FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_hpts.c

     /*-
      * Copyright (c) 2016-2018 Netflix, Inc.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
      * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     */
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_inet.h"
    #include "opt_inet6.h"
    #include "opt_rss.h"
    
    /**
     * Some notes about usage.
     *
     * The tcp_hpts system is designed to provide a high precision timer
     * system for tcp. Its main purpose is to provide a mechanism for
     * pacing packets out onto the wire. It can be used in two ways
     * by a given TCP stack (and those two methods can be used simultaneously).
     *
     * First, and probably the main thing its used by Rack and BBR, it can
     * be used to call tcp_output() of a transport stack at some time in the future.
     * The normal way this is done is that tcp_output() of the stack schedules
     * itself to be called again by calling tcp_hpts_insert(tcpcb, slot). The
     * slot is the time from now that the stack wants to be called but it
     * must be converted to tcp_hpts's notion of slot. This is done with
     * one of the macros HPTS_MS_TO_SLOTS or HPTS_USEC_TO_SLOTS. So a typical
     * call from the tcp_output() routine might look like:
     *
     * tcp_hpts_insert(tp, HPTS_USEC_TO_SLOTS(550));
     *
     * The above would schedule tcp_ouput() to be called in 550 useconds.
     * Note that if using this mechanism the stack will want to add near
     * its top a check to prevent unwanted calls (from user land or the
     * arrival of incoming ack's). So it would add something like:
     *
     * if (tcp_in_hpts(inp))
     *    return;
     *
     * to prevent output processing until the time alotted has gone by.
     * Of course this is a bare bones example and the stack will probably
     * have more consideration then just the above.
     *
     * In order to run input queued segments from the HPTS context the
     * tcp stack must define an input function for
     * tfb_do_queued_segments(). This function understands
     * how to dequeue a array of packets that were input and
     * knows how to call the correct processing routine.
     *
     * Locking in this is important as well so most likely the
     * stack will need to define the tfb_do_segment_nounlock()
     * splitting tfb_do_segment() into two parts. The main processing
     * part that does not unlock the INP and returns a value of 1 or 0.
     * It returns 0 if all is well and the lock was not released. It
     * returns 1 if we had to destroy the TCB (a reset received etc).
     * The remains of tfb_do_segment() then become just a simple call
     * to the tfb_do_segment_nounlock() function and check the return
     * code and possibly unlock.
     *
     * The stack must also set the flag on the INP that it supports this
     * feature i.e. INP_SUPPORTS_MBUFQ. The LRO code recoginizes
     * this flag as well and will queue packets when it is set.
     * There are other flags as well INP_MBUF_QUEUE_READY and
     * INP_DONT_SACK_QUEUE. The first flag tells the LRO code
     * that we are in the pacer for output so there is no
     * need to wake up the hpts system to get immediate
     * input. The second tells the LRO code that its okay
     * if a SACK arrives you can still defer input and let
     * the current hpts timer run (this is usually set when
     * a rack timer is up so we know SACK's are happening
     * on the connection already and don't want to wakeup yet).
     *
     * There is a common functions within the rack_bbr_common code
     * version i.e. ctf_do_queued_segments(). This function
     * knows how to take the input queue of packets from
     * tp->t_in_pkts and process them digging out
     * all the arguments, calling any bpf tap and
     * calling into tfb_do_segment_nounlock(). The common
     * function (ctf_do_queued_segments())  requires that
    * you have defined the tfb_do_segment_nounlock() as
    * described above.
    */
   
   #include <sys/param.h>
   #include <sys/bus.h>
   #include <sys/interrupt.h>
   #include <sys/module.h>
   #include <sys/kernel.h>
   #include <sys/hhook.h>
   #include <sys/malloc.h>
   #include <sys/mbuf.h>
   #include <sys/proc.h>           /* for proc0 declaration */
   #include <sys/socket.h>
   #include <sys/socketvar.h>
   #include <sys/sysctl.h>
   #include <sys/systm.h>
   #include <sys/refcount.h>
   #include <sys/sched.h>
   #include <sys/queue.h>
   #include <sys/smp.h>
   #include <sys/counter.h>
   #include <sys/time.h>
   #include <sys/kthread.h>
   #include <sys/kern_prefetch.h>
   
   #include <vm/uma.h>
   #include <vm/vm.h>
   
   #include <net/route.h>
   #include <net/vnet.h>
   
   #ifdef RSS
   #include <net/netisr.h>
   #include <net/rss_config.h>
   #endif
   
   #define TCPSTATES               /* for logging */
   
   #include <netinet/in.h>
   #include <netinet/in_kdtrace.h>
   #include <netinet/in_pcb.h>
   #include <netinet/ip.h>
   #include <netinet/ip_icmp.h>    /* required for icmp_var.h */
   #include <netinet/icmp_var.h>   /* for ICMP_BANDLIM */
   #include <netinet/ip_var.h>
   #include <netinet/ip6.h>
   #include <netinet6/in6_pcb.h>
   #include <netinet6/ip6_var.h>
   #include <netinet/tcp.h>
   #include <netinet/tcp_fsm.h>
   #include <netinet/tcp_seq.h>
   #include <netinet/tcp_timer.h>
   #include <netinet/tcp_var.h>
   #include <netinet/tcpip.h>
   #include <netinet/cc/cc.h>
   #include <netinet/tcp_hpts.h>
   #include <netinet/tcp_log_buf.h>
   
   #ifdef tcp_offload
   #include <netinet/tcp_offload.h>
   #endif
   
   /*
    * The hpts uses a 102400 wheel. The wheel
    * defines the time in 10 usec increments (102400 x 10).
    * This gives a range of 10usec - 1024ms to place
    * an entry within. If the user requests more than
    * 1.024 second, a remaineder is attached and the hpts
    * when seeing the remainder will re-insert the
    * inpcb forward in time from where it is until
    * the remainder is zero.
    */
   
   #define NUM_OF_HPTSI_SLOTS 102400
   
   /* Each hpts has its own p_mtx which is used for locking */
   #define HPTS_MTX_ASSERT(hpts)   mtx_assert(&(hpts)->p_mtx, MA_OWNED)
   #define HPTS_LOCK(hpts)         mtx_lock(&(hpts)->p_mtx)
   #define HPTS_UNLOCK(hpts)       mtx_unlock(&(hpts)->p_mtx)
   struct tcp_hpts_entry {
           /* Cache line 0x00 */
           struct mtx p_mtx;       /* Mutex for hpts */
           struct timeval p_mysleep;       /* Our min sleep time */
           uint64_t syscall_cnt;
           uint64_t sleeping;      /* What the actual sleep was (if sleeping) */
           uint16_t p_hpts_active; /* Flag that says hpts is awake  */
           uint8_t p_wheel_complete; /* have we completed the wheel arc walk? */
           uint32_t p_curtick;     /* Tick in 10 us the hpts is going to */
           uint32_t p_runningslot; /* Current tick we are at if we are running */
           uint32_t p_prev_slot;   /* Previous slot we were on */
           uint32_t p_cur_slot;    /* Current slot in wheel hpts is draining */
           uint32_t p_nxt_slot;    /* The next slot outside the current range of
                                    * slots that the hpts is running on. */
           int32_t p_on_queue_cnt; /* Count on queue in this hpts */
           uint32_t p_lasttick;    /* Last tick before the current one */
           uint8_t p_direct_wake :1, /* boolean */
                   p_on_min_sleep:1, /* boolean */
                   p_hpts_wake_scheduled:1, /* boolean */
                   p_avail:5;
           uint8_t p_fill[3];        /* Fill to 32 bits */
           /* Cache line 0x40 */
           struct hptsh {
                   TAILQ_HEAD(, inpcb)     head;
                   uint32_t                count;
                   uint32_t                gencnt;
           } *p_hptss;                     /* Hptsi wheel */
           uint32_t p_hpts_sleep_time;     /* Current sleep interval having a max
                                            * of 255ms */
           uint32_t overidden_sleep;       /* what was overrided by min-sleep for logging */
           uint32_t saved_lasttick;        /* for logging */
           uint32_t saved_curtick;         /* for logging */
           uint32_t saved_curslot;         /* for logging */
           uint32_t saved_prev_slot;       /* for logging */
           uint32_t p_delayed_by;  /* How much were we delayed by */
           /* Cache line 0x80 */
           struct sysctl_ctx_list hpts_ctx;
           struct sysctl_oid *hpts_root;
           struct intr_event *ie;
           void *ie_cookie;
           uint16_t p_num;         /* The hpts number one per cpu */
           uint16_t p_cpu;         /* The hpts CPU */
           /* There is extra space in here */
           /* Cache line 0x100 */
           struct callout co __aligned(CACHE_LINE_SIZE);
   }               __aligned(CACHE_LINE_SIZE);
   
   static struct tcp_hptsi {
           struct cpu_group **grps;
           struct tcp_hpts_entry **rp_ent; /* Array of hptss */
           uint32_t *cts_last_ran;
           uint32_t grp_cnt;
           uint32_t rp_num_hptss;  /* Number of hpts threads */
   } tcp_pace;
   
   MALLOC_DEFINE(M_TCPHPTS, "tcp_hpts", "TCP hpts");
   #ifdef RSS
   static int tcp_bind_threads = 1;
   #else
   static int tcp_bind_threads = 2;
   #endif
   static int tcp_use_irq_cpu = 0;
   static uint32_t *cts_last_ran;
   static int hpts_does_tp_logging = 0;
   
   static int32_t tcp_hptsi(struct tcp_hpts_entry *hpts, int from_callout);
   static void tcp_hpts_thread(void *ctx);
   static void tcp_init_hptsi(void *st);
   
   int32_t tcp_min_hptsi_time = DEFAULT_MIN_SLEEP;
   static int conn_cnt_thresh = DEFAULT_CONNECTION_THESHOLD;
   static int32_t dynamic_min_sleep = DYNAMIC_MIN_SLEEP;
   static int32_t dynamic_max_sleep = DYNAMIC_MAX_SLEEP;
   
   
   SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hpts, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
       "TCP Hpts controls");
   SYSCTL_NODE(_net_inet_tcp_hpts, OID_AUTO, stats, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
       "TCP Hpts statistics");
   
   #define timersub(tvp, uvp, vvp)                                         \
           do {                                                            \
                   (vvp)->tv_sec = (tvp)->tv_sec - (uvp)->tv_sec;          \
                   (vvp)->tv_usec = (tvp)->tv_usec - (uvp)->tv_usec;       \
                   if ((vvp)->tv_usec < 0) {                               \
                           (vvp)->tv_sec--;                                \
                           (vvp)->tv_usec += 1000000;                      \
                   }                                                       \
           } while (0)
   
   static int32_t tcp_hpts_precision = 120;
   
   static struct hpts_domain_info {
           int count;
           int cpu[MAXCPU];
   } hpts_domains[MAXMEMDOM];
   
   enum {
           IHPTS_NONE = 0,
           IHPTS_ONQUEUE,
           IHPTS_MOVING,
   };
   
   counter_u64_t hpts_hopelessly_behind;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, hopeless, CTLFLAG_RD,
       &hpts_hopelessly_behind,
       "Number of times hpts could not catch up and was behind hopelessly");
   
   counter_u64_t hpts_loops;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, loops, CTLFLAG_RD,
       &hpts_loops, "Number of times hpts had to loop to catch up");
   
   counter_u64_t back_tosleep;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, no_tcbsfound, CTLFLAG_RD,
       &back_tosleep, "Number of times hpts found no tcbs");
   
   counter_u64_t combined_wheel_wrap;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, comb_wheel_wrap, CTLFLAG_RD,
       &combined_wheel_wrap, "Number of times the wheel lagged enough to have an insert see wrap");
   
   counter_u64_t wheel_wrap;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, wheel_wrap, CTLFLAG_RD,
       &wheel_wrap, "Number of times the wheel lagged enough to have an insert see wrap");
   
   counter_u64_t hpts_direct_call;
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, direct_call, CTLFLAG_RD,
       &hpts_direct_call, "Number of times hpts was called by syscall/trap or other entry");
   
   counter_u64_t hpts_wake_timeout;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, timeout_wakeup, CTLFLAG_RD,
       &hpts_wake_timeout, "Number of times hpts threads woke up via the callout expiring");
   
   counter_u64_t hpts_direct_awakening;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, direct_awakening, CTLFLAG_RD,
       &hpts_direct_awakening, "Number of times hpts threads woke up via the callout expiring");
   
   counter_u64_t hpts_back_tosleep;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, back_tosleep, CTLFLAG_RD,
       &hpts_back_tosleep, "Number of times hpts threads woke up via the callout expiring and went back to sleep no work");
   
   counter_u64_t cpu_uses_flowid;
   counter_u64_t cpu_uses_random;
   
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, cpusel_flowid, CTLFLAG_RD,
       &cpu_uses_flowid, "Number of times when setting cpuid we used the flowid field");
   SYSCTL_COUNTER_U64(_net_inet_tcp_hpts_stats, OID_AUTO, cpusel_random, CTLFLAG_RD,
       &cpu_uses_random, "Number of times when setting cpuid we used the a random value");
   
   TUNABLE_INT("net.inet.tcp.bind_hptss", &tcp_bind_threads);
   TUNABLE_INT("net.inet.tcp.use_irq", &tcp_use_irq_cpu);
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, bind_hptss, CTLFLAG_RD,
       &tcp_bind_threads, 2,
       "Thread Binding tunable");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, use_irq, CTLFLAG_RD,
       &tcp_use_irq_cpu, 0,
       "Use of irq CPU  tunable");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, precision, CTLFLAG_RW,
       &tcp_hpts_precision, 120,
       "Value for PRE() precision of callout");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, cnt_thresh, CTLFLAG_RW,
       &conn_cnt_thresh, 0,
       "How many connections (below) make us use the callout based mechanism");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, logging, CTLFLAG_RW,
       &hpts_does_tp_logging, 0,
       "Do we add to any tp that has logging on pacer logs");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, dyn_minsleep, CTLFLAG_RW,
       &dynamic_min_sleep, 250,
       "What is the dynamic minsleep value?");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, dyn_maxsleep, CTLFLAG_RW,
       &dynamic_max_sleep, 5000,
       "What is the dynamic maxsleep value?");
   
   static int32_t max_pacer_loops = 10;
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, loopmax, CTLFLAG_RW,
       &max_pacer_loops, 10,
       "What is the maximum number of times the pacer will loop trying to catch up");
   
   #define HPTS_MAX_SLEEP_ALLOWED (NUM_OF_HPTSI_SLOTS/2)
   
   static uint32_t hpts_sleep_max = HPTS_MAX_SLEEP_ALLOWED;
   
   static int
   sysctl_net_inet_tcp_hpts_max_sleep(SYSCTL_HANDLER_ARGS)
   {
           int error;
           uint32_t new;
   
           new = hpts_sleep_max;
           error = sysctl_handle_int(oidp, &new, 0, req);
           if (error == 0 && req->newptr) {
                   if ((new < (dynamic_min_sleep/HPTS_TICKS_PER_SLOT)) ||
                        (new > HPTS_MAX_SLEEP_ALLOWED))
                           error = EINVAL;
                   else
                           hpts_sleep_max = new;
           }
           return (error);
   }
   
   static int
   sysctl_net_inet_tcp_hpts_min_sleep(SYSCTL_HANDLER_ARGS)
   {
           int error;
           uint32_t new;
   
           new = tcp_min_hptsi_time;
           error = sysctl_handle_int(oidp, &new, 0, req);
           if (error == 0 && req->newptr) {
                   if (new < LOWEST_SLEEP_ALLOWED)
                           error = EINVAL;
                   else
                           tcp_min_hptsi_time = new;
           }
           return (error);
   }
   
   SYSCTL_PROC(_net_inet_tcp_hpts, OID_AUTO, maxsleep,
       CTLTYPE_UINT | CTLFLAG_RW,
       &hpts_sleep_max, 0,
       &sysctl_net_inet_tcp_hpts_max_sleep, "IU",
       "Maximum time hpts will sleep in slots");
   
   SYSCTL_PROC(_net_inet_tcp_hpts, OID_AUTO, minsleep,
       CTLTYPE_UINT | CTLFLAG_RW,
       &tcp_min_hptsi_time, 0,
       &sysctl_net_inet_tcp_hpts_min_sleep, "IU",
       "The minimum time the hpts must sleep before processing more slots");
   
   static int ticks_indicate_more_sleep = TICKS_INDICATE_MORE_SLEEP;
   static int ticks_indicate_less_sleep = TICKS_INDICATE_LESS_SLEEP;
   static int tcp_hpts_no_wake_over_thresh = 1;
   
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, more_sleep, CTLFLAG_RW,
       &ticks_indicate_more_sleep, 0,
       "If we only process this many or less on a timeout, we need longer sleep on the next callout");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, less_sleep, CTLFLAG_RW,
       &ticks_indicate_less_sleep, 0,
       "If we process this many or more on a timeout, we need less sleep on the next callout");
   SYSCTL_INT(_net_inet_tcp_hpts, OID_AUTO, nowake_over_thresh, CTLFLAG_RW,
       &tcp_hpts_no_wake_over_thresh, 0,
       "When we are over the threshold on the pacer do we prohibit wakeups?");
   
   static void
   tcp_hpts_log(struct tcp_hpts_entry *hpts, struct tcpcb *tp, struct timeval *tv,
                int slots_to_run, int idx, int from_callout)
   {
           union tcp_log_stackspecific log;
           /*
            * Unused logs are
            * 64 bit - delRate, rttProp, bw_inuse
            * 16 bit - cwnd_gain
            *  8 bit - bbr_state, bbr_substate, inhpts;
            */
           memset(&log.u_bbr, 0, sizeof(log.u_bbr));
           log.u_bbr.flex1 = hpts->p_nxt_slot;
           log.u_bbr.flex2 = hpts->p_cur_slot;
           log.u_bbr.flex3 = hpts->p_prev_slot;
           log.u_bbr.flex4 = idx;
           log.u_bbr.flex5 = hpts->p_curtick;
           log.u_bbr.flex6 = hpts->p_on_queue_cnt;
           log.u_bbr.flex7 = hpts->p_cpu;
           log.u_bbr.flex8 = (uint8_t)from_callout;
           log.u_bbr.inflight = slots_to_run;
           log.u_bbr.applimited = hpts->overidden_sleep;
           log.u_bbr.delivered = hpts->saved_curtick;
           log.u_bbr.timeStamp = tcp_tv_to_usectick(tv);
           log.u_bbr.epoch = hpts->saved_curslot;
           log.u_bbr.lt_epoch = hpts->saved_prev_slot;
           log.u_bbr.pkts_out = hpts->p_delayed_by;
           log.u_bbr.lost = hpts->p_hpts_sleep_time;
           log.u_bbr.pacing_gain = hpts->p_cpu;
           log.u_bbr.pkt_epoch = hpts->p_runningslot;
           log.u_bbr.use_lt_bw = 1;
           TCP_LOG_EVENTP(tp, NULL,
                          &tptosocket(tp)->so_rcv,
                          &tptosocket(tp)->so_snd,
                          BBR_LOG_HPTSDIAG, 0,
                          0, &log, false, tv);
   }
   
   static void
   tcp_wakehpts(struct tcp_hpts_entry *hpts)
   {
           HPTS_MTX_ASSERT(hpts);
   
           if (tcp_hpts_no_wake_over_thresh && (hpts->p_on_queue_cnt >= conn_cnt_thresh)) {
                   hpts->p_direct_wake = 0;
                   return;
           }
           if (hpts->p_hpts_wake_scheduled == 0) {
                   hpts->p_hpts_wake_scheduled = 1;
                   swi_sched(hpts->ie_cookie, 0);
           }
   }
   
   static void
   hpts_timeout_swi(void *arg)
   {
           struct tcp_hpts_entry *hpts;
   
           hpts = (struct tcp_hpts_entry *)arg;
           swi_sched(hpts->ie_cookie, 0);
   }
   
   static void
   inp_hpts_insert(struct inpcb *inp, struct tcp_hpts_entry *hpts)
   {
           struct hptsh *hptsh;
   
           INP_WLOCK_ASSERT(inp);
           HPTS_MTX_ASSERT(hpts);
           MPASS(hpts->p_cpu == inp->inp_hpts_cpu);
           MPASS(!(inp->inp_flags & INP_DROPPED));
   
           hptsh = &hpts->p_hptss[inp->inp_hptsslot];
   
           if (inp->inp_in_hpts == IHPTS_NONE) {
                   inp->inp_in_hpts = IHPTS_ONQUEUE;
                   in_pcbref(inp);
           } else if (inp->inp_in_hpts == IHPTS_MOVING) {
                   inp->inp_in_hpts = IHPTS_ONQUEUE;
           } else
                   MPASS(inp->inp_in_hpts == IHPTS_ONQUEUE);
           inp->inp_hpts_gencnt = hptsh->gencnt;
   
           TAILQ_INSERT_TAIL(&hptsh->head, inp, inp_hpts);
           hptsh->count++;
           hpts->p_on_queue_cnt++;
   }
   
   static struct tcp_hpts_entry *
   tcp_hpts_lock(struct inpcb *inp)
   {
           struct tcp_hpts_entry *hpts;
   
           INP_LOCK_ASSERT(inp);
   
           hpts = tcp_pace.rp_ent[inp->inp_hpts_cpu];
           HPTS_LOCK(hpts);
   
           return (hpts);
   }
   
   static void
   inp_hpts_release(struct inpcb *inp)
   {
           bool released __diagused;
   
           inp->inp_in_hpts = IHPTS_NONE;
           released = in_pcbrele_wlocked(inp);
           MPASS(released == false);
   }
   
   /*
    * Called normally with the INP_LOCKED but it
    * does not matter, the hpts lock is the key
    * but the lock order allows us to hold the
    * INP lock and then get the hpts lock.
    */
   void
   tcp_hpts_remove(struct inpcb *inp)
   {
           struct tcp_hpts_entry *hpts;
           struct hptsh *hptsh;
   
           INP_WLOCK_ASSERT(inp);
   
           hpts = tcp_hpts_lock(inp);
           if (inp->inp_in_hpts == IHPTS_ONQUEUE) {
                   hptsh = &hpts->p_hptss[inp->inp_hptsslot];
                   inp->inp_hpts_request = 0;
                   if (__predict_true(inp->inp_hpts_gencnt == hptsh->gencnt)) {
                           TAILQ_REMOVE(&hptsh->head, inp, inp_hpts);
                           MPASS(hptsh->count > 0);
                           hptsh->count--;
                           MPASS(hpts->p_on_queue_cnt > 0);
                           hpts->p_on_queue_cnt--;
                           inp_hpts_release(inp);
                   } else {
                           /*
                            * tcp_hptsi() now owns the TAILQ head of this inp.
                            * Can't TAILQ_REMOVE, just mark it.
                            */
   #ifdef INVARIANTS
                           struct inpcb *tmp;
   
                           TAILQ_FOREACH(tmp, &hptsh->head, inp_hpts)
                                   MPASS(tmp != inp);
   #endif
                           inp->inp_in_hpts = IHPTS_MOVING;
                           inp->inp_hptsslot = -1;
                   }
           } else if (inp->inp_in_hpts == IHPTS_MOVING) {
                   /*
                    * Handle a special race condition:
                    * tcp_hptsi() moves inpcb to detached tailq
                    * tcp_hpts_remove() marks as IHPTS_MOVING, slot = -1
                    * tcp_hpts_insert() sets slot to a meaningful value
                    * tcp_hpts_remove() again (we are here!), then in_pcbdrop()
                    * tcp_hptsi() finds pcb with meaningful slot and INP_DROPPED
                    */
                   inp->inp_hptsslot = -1;
           }
           HPTS_UNLOCK(hpts);
   }
   
   bool
   tcp_in_hpts(struct inpcb *inp)
   {
   
           return (inp->inp_in_hpts == IHPTS_ONQUEUE);
   }
   
   static inline int
   hpts_slot(uint32_t wheel_slot, uint32_t plus)
   {
           /*
            * Given a slot on the wheel, what slot
            * is that plus ticks out?
            */
           KASSERT(wheel_slot < NUM_OF_HPTSI_SLOTS, ("Invalid tick %u not on wheel", wheel_slot));
           return ((wheel_slot + plus) % NUM_OF_HPTSI_SLOTS);
   }
   
   static inline int
   tick_to_wheel(uint32_t cts_in_wticks)
   {
           /*
            * Given a timestamp in ticks (so by
            * default to get it to a real time one
            * would multiply by 10.. i.e the number
            * of ticks in a slot) map it to our limited
            * space wheel.
            */
           return (cts_in_wticks % NUM_OF_HPTSI_SLOTS);
   }
   
   static inline int
   hpts_slots_diff(int prev_slot, int slot_now)
   {
           /*
            * Given two slots that are someplace
            * on our wheel. How far are they apart?
            */
           if (slot_now > prev_slot)
                   return (slot_now - prev_slot);
           else if (slot_now == prev_slot)
                   /*
                    * Special case, same means we can go all of our
                    * wheel less one slot.
                    */
                   return (NUM_OF_HPTSI_SLOTS - 1);
           else
                   return ((NUM_OF_HPTSI_SLOTS - prev_slot) + slot_now);
   }
   
   /*
    * Given a slot on the wheel that is the current time
    * mapped to the wheel (wheel_slot), what is the maximum
    * distance forward that can be obtained without
    * wrapping past either prev_slot or running_slot
    * depending on the htps state? Also if passed
    * a uint32_t *, fill it with the slot location.
    *
    * Note if you do not give this function the current
    * time (that you think it is) mapped to the wheel slot
    * then the results will not be what you expect and
    * could lead to invalid inserts.
    */
   static inline int32_t
   max_slots_available(struct tcp_hpts_entry *hpts, uint32_t wheel_slot, uint32_t *target_slot)
   {
           uint32_t dis_to_travel, end_slot, pacer_to_now, avail_on_wheel;
   
           if ((hpts->p_hpts_active == 1) &&
               (hpts->p_wheel_complete == 0)) {
                   end_slot = hpts->p_runningslot;
                   /* Back up one tick */
                   if (end_slot == 0)
                           end_slot = NUM_OF_HPTSI_SLOTS - 1;
                   else
                           end_slot--;
                   if (target_slot)
                           *target_slot = end_slot;
           } else {
                   /*
                    * For the case where we are
                    * not active, or we have
                    * completed the pass over
                    * the wheel, we can use the
                    * prev tick and subtract one from it. This puts us
                    * as far out as possible on the wheel.
                    */
                   end_slot = hpts->p_prev_slot;
                   if (end_slot == 0)
                           end_slot = NUM_OF_HPTSI_SLOTS - 1;
                   else
                           end_slot--;
                   if (target_slot)
                           *target_slot = end_slot;
                   /*
                    * Now we have close to the full wheel left minus the
                    * time it has been since the pacer went to sleep. Note
                    * that wheel_tick, passed in, should be the current time
                    * from the perspective of the caller, mapped to the wheel.
                    */
                   if (hpts->p_prev_slot != wheel_slot)
                           dis_to_travel = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);
                   else
                           dis_to_travel = 1;
                   /*
                    * dis_to_travel in this case is the space from when the
                    * pacer stopped (p_prev_slot) and where our wheel_slot
                    * is now. To know how many slots we can put it in we
                    * subtract from the wheel size. We would not want
                    * to place something after p_prev_slot or it will
                    * get ran too soon.
                    */
                   return (NUM_OF_HPTSI_SLOTS - dis_to_travel);
           }
           /*
            * So how many slots are open between p_runningslot -> p_cur_slot
            * that is what is currently un-available for insertion. Special
            * case when we are at the last slot, this gets 1, so that
            * the answer to how many slots are available is all but 1.
            */
           if (hpts->p_runningslot == hpts->p_cur_slot)
                   dis_to_travel = 1;
           else
                   dis_to_travel = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
           /*
            * How long has the pacer been running?
            */
           if (hpts->p_cur_slot != wheel_slot) {
                   /* The pacer is a bit late */
                   pacer_to_now = hpts_slots_diff(hpts->p_cur_slot, wheel_slot);
           } else {
                   /* The pacer is right on time, now == pacers start time */
                   pacer_to_now = 0;
           }
           /*
            * To get the number left we can insert into we simply
            * subtract the distance the pacer has to run from how
            * many slots there are.
            */
           avail_on_wheel = NUM_OF_HPTSI_SLOTS - dis_to_travel;
           /*
            * Now how many of those we will eat due to the pacer's
            * time (p_cur_slot) of start being behind the
            * real time (wheel_slot)?
            */
           if (avail_on_wheel <= pacer_to_now) {
                   /*
                    * Wheel wrap, we can't fit on the wheel, that
                    * is unusual the system must be way overloaded!
                    * Insert into the assured slot, and return special
                    * "".
                    */
                   counter_u64_add(combined_wheel_wrap, 1);
                   *target_slot = hpts->p_nxt_slot;
                   return (0);
           } else {
                   /*
                    * We know how many slots are open
                    * on the wheel (the reverse of what
                    * is left to run. Take away the time
                    * the pacer started to now (wheel_slot)
                    * and that tells you how many slots are
                    * open that can be inserted into that won't
                    * be touched by the pacer until later.
                    */
                   return (avail_on_wheel - pacer_to_now);
           }
   }
   
   
   #ifdef INVARIANTS
   static void
   check_if_slot_would_be_wrong(struct tcp_hpts_entry *hpts, struct inpcb *inp, uint32_t inp_hptsslot, int line)
   {
           /*
            * Sanity checks for the pacer with invariants
            * on insert.
            */
           KASSERT(inp_hptsslot < NUM_OF_HPTSI_SLOTS,
                   ("hpts:%p inp:%p slot:%d > max",
                    hpts, inp, inp_hptsslot));
           if ((hpts->p_hpts_active) &&
               (hpts->p_wheel_complete == 0)) {
                   /*
                    * If the pacer is processing a arc
                    * of the wheel, we need to make
                    * sure we are not inserting within
                    * that arc.
                    */
                   int distance, yet_to_run;
   
                   distance = hpts_slots_diff(hpts->p_runningslot, inp_hptsslot);
                   if (hpts->p_runningslot != hpts->p_cur_slot)
                           yet_to_run = hpts_slots_diff(hpts->p_runningslot, hpts->p_cur_slot);
                   else
                           yet_to_run = 0; /* processing last slot */
                   KASSERT(yet_to_run <= distance,
                           ("hpts:%p inp:%p slot:%d distance:%d yet_to_run:%d rs:%d cs:%d",
                            hpts, inp, inp_hptsslot,
                            distance, yet_to_run,
                            hpts->p_runningslot, hpts->p_cur_slot));
           }
   }
   #endif
   
   uint32_t
   tcp_hpts_insert_diag(struct inpcb *inp, uint32_t slot, int32_t line, struct hpts_diag *diag)
   {
           struct tcp_hpts_entry *hpts;
           struct timeval tv;
           uint32_t slot_on, wheel_cts, last_slot, need_new_to = 0;
           int32_t wheel_slot, maxslots;
           bool need_wakeup = false;
   
           INP_WLOCK_ASSERT(inp);
           MPASS(!tcp_in_hpts(inp));
           MPASS(!(inp->inp_flags & INP_DROPPED));
   
           /*
            * We now return the next-slot the hpts will be on, beyond its
            * current run (if up) or where it was when it stopped if it is
            * sleeping.
            */
           hpts = tcp_hpts_lock(inp);
           microuptime(&tv);
           if (diag) {
                   memset(diag, 0, sizeof(struct hpts_diag));
                   diag->p_hpts_active = hpts->p_hpts_active;
                   diag->p_prev_slot = hpts->p_prev_slot;
                   diag->p_runningslot = hpts->p_runningslot;
                   diag->p_nxt_slot = hpts->p_nxt_slot;
                   diag->p_cur_slot = hpts->p_cur_slot;
                   diag->p_curtick = hpts->p_curtick;
                   diag->p_lasttick = hpts->p_lasttick;
                   diag->slot_req = slot;
                   diag->p_on_min_sleep = hpts->p_on_min_sleep;
                   diag->hpts_sleep_time = hpts->p_hpts_sleep_time;
           }
           if (slot == 0) {
                   /* Ok we need to set it on the hpts in the current slot */
                   inp->inp_hpts_request = 0;
                   if ((hpts->p_hpts_active == 0) || (hpts->p_wheel_complete)) {
                           /*
                            * A sleeping hpts we want in next slot to run
                            * note that in this state p_prev_slot == p_cur_slot
                            */
                           inp->inp_hptsslot = hpts_slot(hpts->p_prev_slot, 1);
                           if ((hpts->p_on_min_sleep == 0) &&
                               (hpts->p_hpts_active == 0))
                                   need_wakeup = true;
                   } else
                           inp->inp_hptsslot = hpts->p_runningslot;
                   if (__predict_true(inp->inp_in_hpts != IHPTS_MOVING))
                           inp_hpts_insert(inp, hpts);
                   if (need_wakeup) {
                           /*
                            * Activate the hpts if it is sleeping and its
                            * timeout is not 1.
                            */
                           hpts->p_direct_wake = 1;
                           tcp_wakehpts(hpts);
                   }
                   slot_on = hpts->p_nxt_slot;
                   HPTS_UNLOCK(hpts);
   
                   return (slot_on);
           }
           /* Get the current time relative to the wheel */
           wheel_cts = tcp_tv_to_hptstick(&tv);
           /* Map it onto the wheel */
           wheel_slot = tick_to_wheel(wheel_cts);
           /* Now what's the max we can place it at? */
           maxslots = max_slots_available(hpts, wheel_slot, &last_slot);
           if (diag) {
                   diag->wheel_slot = wheel_slot;
                   diag->maxslots = maxslots;
                   diag->wheel_cts = wheel_cts;
           }
           if (maxslots == 0) {
                   /* The pacer is in a wheel wrap behind, yikes! */
                   if (slot > 1) {
                           /*
                            * Reduce by 1 to prevent a forever loop in
                            * case something else is wrong. Note this
                            * probably does not hurt because the pacer
                            * if its true is so far behind we will be
                            * > 1second late calling anyway.
                            */
                           slot--;
                   }
                   inp->inp_hptsslot = last_slot;
                   inp->inp_hpts_request = slot;
           } else  if (maxslots >= slot) {
                   /* It all fits on the wheel */
                   inp->inp_hpts_request = 0;
                   inp->inp_hptsslot = hpts_slot(wheel_slot, slot);
           } else {
                   /* It does not fit */
                   inp->inp_hpts_request = slot - maxslots;
                   inp->inp_hptsslot = last_slot;
           }
           if (diag) {
                   diag->slot_remaining = inp->inp_hpts_request;
                   diag->inp_hptsslot = inp->inp_hptsslot;
           }
   #ifdef INVARIANTS
           check_if_slot_would_be_wrong(hpts, inp, inp->inp_hptsslot, line);
   #endif
           if (__predict_true(inp->inp_in_hpts != IHPTS_MOVING))
                   inp_hpts_insert(inp, hpts);
           if ((hpts->p_hpts_active == 0) &&
               (inp->inp_hpts_request == 0) &&
               (hpts->p_on_min_sleep == 0)) {
                   /*
                    * The hpts is sleeping and NOT on a minimum
                    * sleep time, we need to figure out where
                    * it will wake up at and if we need to reschedule
                    * its time-out.
                    */
                   uint32_t have_slept, yet_to_sleep;
   
                   /* Now do we need to restart the hpts's timer? */
                   have_slept = hpts_slots_diff(hpts->p_prev_slot, wheel_slot);
                   if (have_slept < hpts->p_hpts_sleep_time)
                           yet_to_sleep = hpts->p_hpts_sleep_time - have_slept;
                   else {
                           /* We are over-due */
                           yet_to_sleep = 0;
                           need_wakeup = 1;
                   }
                   if (diag) {
                           diag->have_slept = have_slept;
                           diag->yet_to_sleep = yet_to_sleep;
                   }
                   if (yet_to_sleep &&
                       (yet_to_sleep > slot)) {
                           /*
                            * We need to reschedule the hpts's time-out.
                            */
                           hpts->p_hpts_sleep_time = slot;
                           need_new_to = slot * HPTS_TICKS_PER_SLOT;
                   }
           }
           /*
            * Now how far is the hpts sleeping to? if active is 1, its
            * up and ticking we do nothing, otherwise we may need to
            * reschedule its callout if need_new_to is set from above.
            */
           if (need_wakeup) {
                   hpts->p_direct_wake = 1;
                   tcp_wakehpts(hpts);
                   if (diag) {
                           diag->need_new_to = 0;
                           diag->co_ret = 0xffff0000;
                   }
           } else if (need_new_to) {
                   int32_t co_ret;
                   struct timeval tv;
                   sbintime_t sb;
   
                   tv.tv_sec = 0;
                   tv.tv_usec = 0;
                   while (need_new_to > HPTS_USEC_IN_SEC) {
                           tv.tv_sec++;
                           need_new_to -= HPTS_USEC_IN_SEC;
                   }
                   tv.tv_usec = need_new_to;
                   sb = tvtosbt(tv);
                   co_ret = callout_reset_sbt_on(&hpts->co, sb, 0,
                                                 hpts_timeout_swi, hpts, hpts->p_cpu,
                                                 (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
                   if (diag) {
                           diag->need_new_to = need_new_to;
                           diag->co_ret = co_ret;
                   }
           }
           slot_on = hpts->p_nxt_slot;
           HPTS_UNLOCK(hpts);
   
           return (slot_on);
   }
   
   uint16_t
   hpts_random_cpu(struct inpcb *inp){
           /*
            * No flow type set distribute the load randomly.
            */
           uint16_t cpuid;
           uint32_t ran;
   
           /*
            * Shortcut if it is already set. XXXGL: does it happen?
            */
           if (inp->inp_hpts_cpu_set) {
                   return (inp->inp_hpts_cpu);
           }
           /* Nothing set use a random number */
           ran = arc4random();
           cpuid = (((ran & 0xffff) % mp_ncpus) % tcp_pace.rp_num_hptss);
           return (cpuid);
   }
   
   static uint16_t
   hpts_cpuid(struct inpcb *inp, int *failed)
   {
           u_int cpuid;
  #ifdef NUMA
          struct hpts_domain_info *di;
  #endif
  
          *failed = 0;
          if (inp->inp_hpts_cpu_set) {
                  return (inp->inp_hpts_cpu);
          }
          /*
           * If we are using the irq cpu set by LRO or
           * the driver then it overrides all other domains.
           */
          if (tcp_use_irq_cpu) {
                  if (inp->inp_irq_cpu_set == 0) {
                          *failed = 1;
                          return(0);
                  }
                  return(inp->inp_irq_cpu);
          }
          /* If one is set the other must be the same */
  #ifdef RSS
          cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
          if (cpuid == NETISR_CPUID_NONE)
                  return (hpts_random_cpu(inp));
          else
                  return (cpuid);
  #endif
          /*
           * We don't have a flowid -> cpuid mapping, so cheat and just map
           * unknown cpuids to curcpu.  Not the best, but apparently better
           * than defaulting to swi 0.
           */
          if (inp->inp_flowtype == M_HASHTYPE_NONE) {
                  counter_u64_add(cpu_uses_random, 1);
                  return (hpts_random_cpu(inp));
          }
          /*
           * Hash to a thread based on the flowid.  If we are using numa,
           * then restrict the hash to the numa domain where the inp lives.
           */
  
  #ifdef NUMA
          if ((vm_ndomains == 1) ||
              (inp->inp_numa_domain == M_NODOM)) {
  #endif
                  cpuid = inp->inp_flowid % mp_ncpus;
  #ifdef NUMA
          } else {
                  /* Hash into the cpu's that use that domain */
                  di = &hpts_domains[inp->inp_numa_domain];
                  cpuid = di->cpu[inp->inp_flowid % di->count];
          }
  #endif
          counter_u64_add(cpu_uses_flowid, 1);
          return (cpuid);
  }
  
  #ifdef not_longer_used_gleb
  static void
  tcp_drop_in_pkts(struct tcpcb *tp)
  {
          struct mbuf *m, *n;
  
          m = tp->t_in_pkt;
          if (m)
                  n = m->m_nextpkt;
          else
                  n = NULL;
          tp->t_in_pkt = NULL;
          while (m) {
                  m_freem(m);
                  m = n;
                  if (m)
                          n = m->m_nextpkt;
          }
  }
  #endif
  
  static void
  tcp_hpts_set_max_sleep(struct tcp_hpts_entry *hpts, int wrap_loop_cnt)
  {
          uint32_t t = 0, i;
  
          if ((hpts->p_on_queue_cnt) && (wrap_loop_cnt < 2)) {
                  /*
                   * Find next slot that is occupied and use that to
                   * be the sleep time.
                   */
                  for (i = 0, t = hpts_slot(hpts->p_cur_slot, 1); i < NUM_OF_HPTSI_SLOTS; i++) {
                          if (TAILQ_EMPTY(&hpts->p_hptss[t].head) == 0) {
                                  break;
                          }
                          t = (t + 1) % NUM_OF_HPTSI_SLOTS;
                  }
                  KASSERT((i != NUM_OF_HPTSI_SLOTS), ("Hpts:%p cnt:%d but none found", hpts, hpts->p_on_queue_cnt));
                  hpts->p_hpts_sleep_time = min((i + 1), hpts_sleep_max);
          } else {
                  /* No one on the wheel sleep for all but 400 slots or sleep max  */
                  hpts->p_hpts_sleep_time = hpts_sleep_max;
          }
  }
  
  static int32_t
  tcp_hptsi(struct tcp_hpts_entry *hpts, int from_callout)
  {
          struct tcpcb *tp;
          struct inpcb *inp;
          struct timeval tv;
          int32_t slots_to_run, i, error;
          int32_t loop_cnt = 0;
          int32_t did_prefetch = 0;
          int32_t prefetch_ninp = 0;
          int32_t prefetch_tp = 0;
          int32_t wrap_loop_cnt = 0;
          int32_t slot_pos_of_endpoint = 0;
          int32_t orig_exit_slot;
          int8_t completed_measure = 0, seen_endpoint = 0;
  
          HPTS_MTX_ASSERT(hpts);
          NET_EPOCH_ASSERT();
          /* record previous info for any logging */
          hpts->saved_lasttick = hpts->p_lasttick;
          hpts->saved_curtick = hpts->p_curtick;
          hpts->saved_curslot = hpts->p_cur_slot;
          hpts->saved_prev_slot = hpts->p_prev_slot;
  
          hpts->p_lasttick = hpts->p_curtick;
          hpts->p_curtick = tcp_gethptstick(&tv);
          cts_last_ran[hpts->p_num] = tcp_tv_to_usectick(&tv);
          orig_exit_slot = hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
          if ((hpts->p_on_queue_cnt == 0) ||
              (hpts->p_lasttick == hpts->p_curtick)) {
                  /*
                   * No time has yet passed,
                   * or nothing to do.
                   */
                  hpts->p_prev_slot = hpts->p_cur_slot;
                  hpts->p_lasttick = hpts->p_curtick;
                  goto no_run;
          }
  again:
          hpts->p_wheel_complete = 0;
          HPTS_MTX_ASSERT(hpts);
          slots_to_run = hpts_slots_diff(hpts->p_prev_slot, hpts->p_cur_slot);
          if (((hpts->p_curtick - hpts->p_lasttick) >
               ((NUM_OF_HPTSI_SLOTS-1) * HPTS_TICKS_PER_SLOT)) &&
              (hpts->p_on_queue_cnt != 0)) {
                  /*
                   * Wheel wrap is occuring, basically we
                   * are behind and the distance between
                   * run's has spread so much it has exceeded
                   * the time on the wheel (1.024 seconds). This
                   * is ugly and should NOT be happening. We
                   * need to run the entire wheel. We last processed
                   * p_prev_slot, so that needs to be the last slot
                   * we run. The next slot after that should be our
                   * reserved first slot for new, and then starts
                   * the running position. Now the problem is the
                   * reserved "not to yet" place does not exist
                   * and there may be inp's in there that need
                   * running. We can merge those into the
                   * first slot at the head.
                   */
                  wrap_loop_cnt++;
                  hpts->p_nxt_slot = hpts_slot(hpts->p_prev_slot, 1);
                  hpts->p_runningslot = hpts_slot(hpts->p_prev_slot, 2);
                  /*
                   * Adjust p_cur_slot to be where we are starting from
                   * hopefully we will catch up (fat chance if something
                   * is broken this bad :( )
                   */
                  hpts->p_cur_slot = hpts->p_prev_slot;
                  /*
                   * The next slot has guys to run too, and that would
                   * be where we would normally start, lets move them into
                   * the next slot (p_prev_slot + 2) so that we will
                   * run them, the extra 10usecs of late (by being
                   * put behind) does not really matter in this situation.
                   */
                  TAILQ_FOREACH(inp, &hpts->p_hptss[hpts->p_nxt_slot].head,
                      inp_hpts) {
                          MPASS(inp->inp_hptsslot == hpts->p_nxt_slot);
                          MPASS(inp->inp_hpts_gencnt ==
                              hpts->p_hptss[hpts->p_nxt_slot].gencnt);
                          MPASS(inp->inp_in_hpts == IHPTS_ONQUEUE);
  
                          /*
                           * Update gencnt and nextslot accordingly to match
                           * the new location. This is safe since it takes both
                           * the INP lock and the pacer mutex to change the
                           * inp_hptsslot and inp_hpts_gencnt.
                           */
                          inp->inp_hpts_gencnt =
                              hpts->p_hptss[hpts->p_runningslot].gencnt;
                          inp->inp_hptsslot = hpts->p_runningslot;
                  }
                  TAILQ_CONCAT(&hpts->p_hptss[hpts->p_runningslot].head,
                      &hpts->p_hptss[hpts->p_nxt_slot].head, inp_hpts);
                  hpts->p_hptss[hpts->p_runningslot].count +=
                      hpts->p_hptss[hpts->p_nxt_slot].count;
                  hpts->p_hptss[hpts->p_nxt_slot].count = 0;
                  hpts->p_hptss[hpts->p_nxt_slot].gencnt++;
                  slots_to_run = NUM_OF_HPTSI_SLOTS - 1;
                  counter_u64_add(wheel_wrap, 1);
          } else {
                  /*
                   * Nxt slot is always one after p_runningslot though
                   * its not used usually unless we are doing wheel wrap.
                   */
                  hpts->p_nxt_slot = hpts->p_prev_slot;
                  hpts->p_runningslot = hpts_slot(hpts->p_prev_slot, 1);
          }
          if (hpts->p_on_queue_cnt == 0) {
                  goto no_one;
          }
          for (i = 0; i < slots_to_run; i++) {
                  struct inpcb *inp, *ninp;
                  TAILQ_HEAD(, inpcb) head = TAILQ_HEAD_INITIALIZER(head);
                  struct hptsh *hptsh;
                  uint32_t runningslot;
  
                  /*
                   * Calculate our delay, if there are no extra ticks there
                   * was not any (i.e. if slots_to_run == 1, no delay).
                   */
                  hpts->p_delayed_by = (slots_to_run - (i + 1)) *
                      HPTS_TICKS_PER_SLOT;
  
                  runningslot = hpts->p_runningslot;
                  hptsh = &hpts->p_hptss[runningslot];
                  TAILQ_SWAP(&head, &hptsh->head, inpcb, inp_hpts);
                  hpts->p_on_queue_cnt -= hptsh->count;
                  hptsh->count = 0;
                  hptsh->gencnt++;
  
                  HPTS_UNLOCK(hpts);
  
                  TAILQ_FOREACH_SAFE(inp, &head, inp_hpts, ninp) {
                          bool set_cpu;
  
                          if (ninp != NULL) {
                                  /* We prefetch the next inp if possible */
                                  kern_prefetch(ninp, &prefetch_ninp);
                                  prefetch_ninp = 1;
                          }
  
                          /* For debugging */
                          if (seen_endpoint == 0) {
                                  seen_endpoint = 1;
                                  orig_exit_slot = slot_pos_of_endpoint =
                                      runningslot;
                          } else if (completed_measure == 0) {
                                  /* Record the new position */
                                  orig_exit_slot = runningslot;
                          }
  
                          INP_WLOCK(inp);
                          if (inp->inp_hpts_cpu_set == 0) {
                                  set_cpu = true;
                          } else {
                                  set_cpu = false;
                          }
  
                          if (__predict_false(inp->inp_in_hpts == IHPTS_MOVING)) {
                                  if (inp->inp_hptsslot == -1) {
                                          inp->inp_in_hpts = IHPTS_NONE;
                                          if (in_pcbrele_wlocked(inp) == false)
                                                  INP_WUNLOCK(inp);
                                  } else {
                                          HPTS_LOCK(hpts);
                                          inp_hpts_insert(inp, hpts);
                                          HPTS_UNLOCK(hpts);
                                          INP_WUNLOCK(inp);
                                  }
                                  continue;
                          }
  
                          MPASS(inp->inp_in_hpts == IHPTS_ONQUEUE);
                          MPASS(!(inp->inp_flags & INP_DROPPED));
                          KASSERT(runningslot == inp->inp_hptsslot,
                                  ("Hpts:%p inp:%p slot mis-aligned %u vs %u",
                                   hpts, inp, runningslot, inp->inp_hptsslot));
  
                          if (inp->inp_hpts_request) {
                                  /*
                                   * This guy is deferred out further in time
                                   * then our wheel had available on it.
                                   * Push him back on the wheel or run it
                                   * depending.
                                   */
                                  uint32_t maxslots, last_slot, remaining_slots;
  
                                  remaining_slots = slots_to_run - (i + 1);
                                  if (inp->inp_hpts_request > remaining_slots) {
                                          HPTS_LOCK(hpts);
                                          /*
                                           * How far out can we go?
                                           */
                                          maxslots = max_slots_available(hpts,
                                              hpts->p_cur_slot, &last_slot);
                                          if (maxslots >= inp->inp_hpts_request) {
                                                  /* We can place it finally to
                                                   * be processed.  */
                                                  inp->inp_hptsslot = hpts_slot(
                                                      hpts->p_runningslot,
                                                      inp->inp_hpts_request);
                                                  inp->inp_hpts_request = 0;
                                          } else {
                                                  /* Work off some more time */
                                                  inp->inp_hptsslot = last_slot;
                                                  inp->inp_hpts_request -=
                                                      maxslots;
                                          }
                                          inp_hpts_insert(inp, hpts);
                                          HPTS_UNLOCK(hpts);
                                          INP_WUNLOCK(inp);
                                          continue;
                                  }
                                  inp->inp_hpts_request = 0;
                                  /* Fall through we will so do it now */
                          }
  
                          inp_hpts_release(inp);
                          tp = intotcpcb(inp);
                          MPASS(tp);
                          if (set_cpu) {
                                  /*
                                   * Setup so the next time we will move to
                                   * the right CPU. This should be a rare
                                   * event. It will sometimes happens when we
                                   * are the client side (usually not the
                                   * server). Somehow tcp_output() gets called
                                   * before the tcp_do_segment() sets the
                                   * intial state. This means the r_cpu and
                                   * r_hpts_cpu is 0. We get on the hpts, and
                                   * then tcp_input() gets called setting up
                                   * the r_cpu to the correct value. The hpts
                                   * goes off and sees the mis-match. We
                                   * simply correct it here and the CPU will
                                   * switch to the new hpts nextime the tcb
                                   * gets added to the hpts (not this one)
                                   * :-)
                                   */
                                  tcp_set_hpts(inp);
                          }
                          CURVNET_SET(inp->inp_vnet);
                          /* Lets do any logging that we might want to */
                          if (hpts_does_tp_logging && (tp->t_logstate != TCP_LOG_STATE_OFF)) {
                                  tcp_hpts_log(hpts, tp, &tv, slots_to_run, i, from_callout);
                          }
  
                          if (tp->t_fb_ptr != NULL) {
                                  kern_prefetch(tp->t_fb_ptr, &did_prefetch);
                                  did_prefetch = 1;
                          }
                          if ((inp->inp_flags2 & INP_SUPPORTS_MBUFQ) && tp->t_in_pkt) {
                                  error = (*tp->t_fb->tfb_do_queued_segments)(inp->inp_socket, tp, 0);
                                  if (error) {
                                          /* The input killed the connection */
                                          goto skip_pacing;
                                  }
                          }
                          inp->inp_hpts_calls = 1;
                          error = tcp_output(tp);
                          if (error < 0)
                                  goto skip_pacing;
                          inp->inp_hpts_calls = 0;
                          if (ninp) {
                                  /*
                                   * If we have a nxt inp, see if we can
                                   * prefetch it. Note this may seem
                                   * "risky" since we have no locks (other
                                   * than the previous inp) and there no
                                   * assurance that ninp was not pulled while
                                   * we were processing inp and freed. If this
                                   * occurred it could mean that either:
                                   *
                                   * a) Its NULL (which is fine we won't go
                                   * here) <or> b) Its valid (which is cool we
                                   * will prefetch it) <or> c) The inp got
                                   * freed back to the slab which was
                                   * reallocated. Then the piece of memory was
                                   * re-used and something else (not an
                                   * address) is in inp_ppcb. If that occurs
                                   * we don't crash, but take a TLB shootdown
                                   * performance hit (same as if it was NULL
                                   * and we tried to pre-fetch it).
                                   *
                                   * Considering that the likelyhood of <c> is
                                   * quite rare we will take a risk on doing
                                   * this. If performance drops after testing
                                   * we can always take this out. NB: the
                                   * kern_prefetch on amd64 actually has
                                   * protection against a bad address now via
                                   * the DMAP_() tests. This will prevent the
                                   * TLB hit, and instead if <c> occurs just
                                   * cause us to load cache with a useless
                                   * address (to us).
                                   *
                                   * XXXGL: with tcpcb == inpcb, I'm unsure this
                                   * prefetch is still correct and useful.
                                   */
                                  kern_prefetch(ninp, &prefetch_tp);
                                  prefetch_tp = 1;
                          }
                          INP_WUNLOCK(inp);
                  skip_pacing:
                          CURVNET_RESTORE();
                  }
                  if (seen_endpoint) {
                          /*
                           * We now have a accurate distance between
                           * slot_pos_of_endpoint <-> orig_exit_slot
                           * to tell us how late we were, orig_exit_slot
                           * is where we calculated the end of our cycle to
                           * be when we first entered.
                           */
                          completed_measure = 1;
                  }
                  HPTS_LOCK(hpts);
                  hpts->p_runningslot++;
                  if (hpts->p_runningslot >= NUM_OF_HPTSI_SLOTS) {
                          hpts->p_runningslot = 0;
                  }
          }
  no_one:
          HPTS_MTX_ASSERT(hpts);
          hpts->p_delayed_by = 0;
          /*
           * Check to see if we took an excess amount of time and need to run
           * more ticks (if we did not hit eno-bufs).
           */
          hpts->p_prev_slot = hpts->p_cur_slot;
          hpts->p_lasttick = hpts->p_curtick;
          if ((from_callout == 0) || (loop_cnt > max_pacer_loops)) {
                  /*
                   * Something is serious slow we have
                   * looped through processing the wheel
                   * and by the time we cleared the
                   * needs to run max_pacer_loops time
                   * we still needed to run. That means
                   * the system is hopelessly behind and
                   * can never catch up :(
                   *
                   * We will just lie to this thread
                   * and let it thing p_curtick is
                   * correct. When it next awakens
                   * it will find itself further behind.
                   */
                  if (from_callout)
                          counter_u64_add(hpts_hopelessly_behind, 1);
                  goto no_run;
          }
          hpts->p_curtick = tcp_gethptstick(&tv);
          hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
          if (seen_endpoint == 0) {
                  /* We saw no endpoint but we may be looping */
                  orig_exit_slot = hpts->p_cur_slot;
          }
          if ((wrap_loop_cnt < 2) &&
              (hpts->p_lasttick != hpts->p_curtick)) {
                  counter_u64_add(hpts_loops, 1);
                  loop_cnt++;
                  goto again;
          }
  no_run:
          cts_last_ran[hpts->p_num] = tcp_tv_to_usectick(&tv);
          /*
           * Set flag to tell that we are done for
           * any slot input that happens during
           * input.
           */
          hpts->p_wheel_complete = 1;
          /*
           * Now did we spend too long running input and need to run more ticks?
           * Note that if wrap_loop_cnt < 2 then we should have the conditions
           * in the KASSERT's true. But if the wheel is behind i.e. wrap_loop_cnt
           * is greater than 2, then the condtion most likely are *not* true.
           * Also if we are called not from the callout, we don't run the wheel
           * multiple times so the slots may not align either.
           */
          KASSERT(((hpts->p_prev_slot == hpts->p_cur_slot) ||
                   (wrap_loop_cnt >= 2) || (from_callout == 0)),
                  ("H:%p p_prev_slot:%u not equal to p_cur_slot:%u", hpts,
                   hpts->p_prev_slot, hpts->p_cur_slot));
          KASSERT(((hpts->p_lasttick == hpts->p_curtick)
                   || (wrap_loop_cnt >= 2) || (from_callout == 0)),
                  ("H:%p p_lasttick:%u not equal to p_curtick:%u", hpts,
                   hpts->p_lasttick, hpts->p_curtick));
          if (from_callout && (hpts->p_lasttick != hpts->p_curtick)) {
                  hpts->p_curtick = tcp_gethptstick(&tv);
                  counter_u64_add(hpts_loops, 1);
                  hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
                  goto again;
          }
  
          if (from_callout){
                  tcp_hpts_set_max_sleep(hpts, wrap_loop_cnt);
          }
          if (seen_endpoint)
                  return(hpts_slots_diff(slot_pos_of_endpoint, orig_exit_slot));
          else
                  return (0);
  }
  
  void
  __tcp_set_hpts(struct inpcb *inp, int32_t line)
  {
          struct tcp_hpts_entry *hpts;
          int failed;
  
          INP_WLOCK_ASSERT(inp);
          hpts = tcp_hpts_lock(inp);
          if ((inp->inp_in_hpts == 0) &&
              (inp->inp_hpts_cpu_set == 0)) {
                  inp->inp_hpts_cpu = hpts_cpuid(inp, &failed);
                  if (failed == 0)
                          inp->inp_hpts_cpu_set = 1;
          }
          mtx_unlock(&hpts->p_mtx);
  }
  
  static void
  __tcp_run_hpts(struct tcp_hpts_entry *hpts)
  {
          int ticks_ran;
  
          if (hpts->p_hpts_active) {
                  /* Already active */
                  return;
          }
          if (mtx_trylock(&hpts->p_mtx) == 0) {
                  /* Someone else got the lock */
                  return;
          }
          if (hpts->p_hpts_active)
                  goto out_with_mtx;
          hpts->syscall_cnt++;
          counter_u64_add(hpts_direct_call, 1);
          hpts->p_hpts_active = 1;
          ticks_ran = tcp_hptsi(hpts, 0);
          /* We may want to adjust the sleep values here */
          if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                  if (ticks_ran > ticks_indicate_less_sleep) {
                          struct timeval tv;
                          sbintime_t sb;
  
                          hpts->p_mysleep.tv_usec /= 2;
                          if (hpts->p_mysleep.tv_usec < dynamic_min_sleep)
                                  hpts->p_mysleep.tv_usec = dynamic_min_sleep;
                          /* Reschedule with new to value */
                          tcp_hpts_set_max_sleep(hpts, 0);
                          tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
                          /* Validate its in the right ranges */
                          if (tv.tv_usec < hpts->p_mysleep.tv_usec) {
                                  hpts->overidden_sleep = tv.tv_usec;
                                  tv.tv_usec = hpts->p_mysleep.tv_usec;
                          } else if (tv.tv_usec > dynamic_max_sleep) {
                                  /* Lets not let sleep get above this value */
                                  hpts->overidden_sleep = tv.tv_usec;
                                  tv.tv_usec = dynamic_max_sleep;
                          }
                          /*
                           * In this mode the timer is a backstop to
                           * all the userret/lro_flushes so we use
                           * the dynamic value and set the on_min_sleep
                           * flag so we will not be awoken.
                           */
                          sb = tvtosbt(tv);
                          /* Store off to make visible the actual sleep time */
                          hpts->sleeping = tv.tv_usec;
                          callout_reset_sbt_on(&hpts->co, sb, 0,
                                               hpts_timeout_swi, hpts, hpts->p_cpu,
                                               (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
                  } else if (ticks_ran < ticks_indicate_more_sleep) {
                          /* For the further sleep, don't reschedule  hpts */
                          hpts->p_mysleep.tv_usec *= 2;
                          if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                  hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                  }
                  hpts->p_on_min_sleep = 1;
          }
          hpts->p_hpts_active = 0;
  out_with_mtx:
          HPTS_MTX_ASSERT(hpts);
          mtx_unlock(&hpts->p_mtx);
  }
  
  static struct tcp_hpts_entry *
  tcp_choose_hpts_to_run(void)
  {
          int i, oldest_idx, start, end;
          uint32_t cts, time_since_ran, calc;
  
          cts = tcp_get_usecs(NULL);
          time_since_ran = 0;
          /* Default is all one group */
          start = 0;
          end = tcp_pace.rp_num_hptss;
          /*
           * If we have more than one L3 group figure out which one
           * this CPU is in.
           */
          if (tcp_pace.grp_cnt > 1) {
                  for (i = 0; i < tcp_pace.grp_cnt; i++) {
                          if (CPU_ISSET(curcpu, &tcp_pace.grps[i]->cg_mask)) {
                                  start = tcp_pace.grps[i]->cg_first;
                                  end = (tcp_pace.grps[i]->cg_last + 1);
                                  break;
                          }
                  }
          }
          oldest_idx = -1;
          for (i = start; i < end; i++) {
                  if (TSTMP_GT(cts, cts_last_ran[i]))
                          calc = cts - cts_last_ran[i];
                  else
                          calc = 0;
                  if (calc > time_since_ran) {
                          oldest_idx = i;
                          time_since_ran = calc;
                  }
          }
          if (oldest_idx >= 0)
                  return(tcp_pace.rp_ent[oldest_idx]);
          else
                  return(tcp_pace.rp_ent[(curcpu % tcp_pace.rp_num_hptss)]);
  }
  
  
  void
  tcp_run_hpts(void)
  {
          static struct tcp_hpts_entry *hpts;
          struct epoch_tracker et;
  
          NET_EPOCH_ENTER(et);
          hpts = tcp_choose_hpts_to_run();
          __tcp_run_hpts(hpts);
          NET_EPOCH_EXIT(et);
  }
  
  
  static void
  tcp_hpts_thread(void *ctx)
  {
          struct tcp_hpts_entry *hpts;
          struct epoch_tracker et;
          struct timeval tv;
          sbintime_t sb;
          int ticks_ran;
  
          hpts = (struct tcp_hpts_entry *)ctx;
          mtx_lock(&hpts->p_mtx);
          if (hpts->p_direct_wake) {
                  /* Signaled by input or output with low occupancy count. */
                  callout_stop(&hpts->co);
                  counter_u64_add(hpts_direct_awakening, 1);
          } else {
                  /* Timed out, the normal case. */
                  counter_u64_add(hpts_wake_timeout, 1);
                  if (callout_pending(&hpts->co) ||
                      !callout_active(&hpts->co)) {
                          mtx_unlock(&hpts->p_mtx);
                          return;
                  }
          }
          callout_deactivate(&hpts->co);
          hpts->p_hpts_wake_scheduled = 0;
          NET_EPOCH_ENTER(et);
          if (hpts->p_hpts_active) {
                  /*
                   * We are active already. This means that a syscall
                   * trap or LRO is running in behalf of hpts. In that case
                   * we need to double our timeout since there seems to be
                   * enough activity in the system that we don't need to
                   * run as often (if we were not directly woken).
                   */
                  if (hpts->p_direct_wake == 0) {
                          counter_u64_add(hpts_back_tosleep, 1);
                          if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                                  hpts->p_mysleep.tv_usec *= 2;
                                  if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                          hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                                  tv.tv_usec = hpts->p_mysleep.tv_usec;
                                  hpts->p_on_min_sleep = 1;
                          } else {
                                  /*
                                   * Here we have low count on the wheel, but
                                   * somehow we still collided with one of the
                                   * connections. Lets go back to sleep for a
                                   * min sleep time, but clear the flag so we
                                   * can be awoken by insert.
                                   */
                                  hpts->p_on_min_sleep = 0;
                                  tv.tv_usec = tcp_min_hptsi_time;
                          }
                  } else {
                          /*
                           * Directly woken most likely to reset the
                           * callout time.
                           */
                          tv.tv_sec = 0;
                          tv.tv_usec = hpts->p_mysleep.tv_usec;
                  }
                  goto back_to_sleep;
          }
          hpts->sleeping = 0;
          hpts->p_hpts_active = 1;
          ticks_ran = tcp_hptsi(hpts, 1);
          tv.tv_sec = 0;
          tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
          if (hpts->p_on_queue_cnt >= conn_cnt_thresh) {
                  if(hpts->p_direct_wake == 0) {
                          /*
                           * Only adjust sleep time if we were
                           * called from the callout i.e. direct_wake == 0.
                           */
                          if (ticks_ran < ticks_indicate_more_sleep) {
                                  hpts->p_mysleep.tv_usec *= 2;
                                  if (hpts->p_mysleep.tv_usec > dynamic_max_sleep)
                                          hpts->p_mysleep.tv_usec = dynamic_max_sleep;
                          } else if (ticks_ran > ticks_indicate_less_sleep) {
                                  hpts->p_mysleep.tv_usec /= 2;
                                  if (hpts->p_mysleep.tv_usec < dynamic_min_sleep)
                                          hpts->p_mysleep.tv_usec = dynamic_min_sleep;
                          }
                  }
                  if (tv.tv_usec < hpts->p_mysleep.tv_usec) {
                          hpts->overidden_sleep = tv.tv_usec;
                          tv.tv_usec = hpts->p_mysleep.tv_usec;
                  } else if (tv.tv_usec > dynamic_max_sleep) {
                          /* Lets not let sleep get above this value */
                          hpts->overidden_sleep = tv.tv_usec;
                          tv.tv_usec = dynamic_max_sleep;
                  }
                  /*
                   * In this mode the timer is a backstop to
                   * all the userret/lro_flushes so we use
                   * the dynamic value and set the on_min_sleep
                   * flag so we will not be awoken.
                   */
                  hpts->p_on_min_sleep = 1;
          } else if (hpts->p_on_queue_cnt == 0)  {
                  /*
                   * No one on the wheel, please wake us up
                   * if you insert on the wheel.
                   */
                  hpts->p_on_min_sleep = 0;
                  hpts->overidden_sleep = 0;
          } else {
                  /*
                   * We hit here when we have a low number of
                   * clients on the wheel (our else clause).
                   * We may need to go on min sleep, if we set
                   * the flag we will not be awoken if someone
                   * is inserted ahead of us. Clearing the flag
                   * means we can be awoken. This is "old mode"
                   * where the timer is what runs hpts mainly.
                   */
                  if (tv.tv_usec < tcp_min_hptsi_time) {
                          /*
                           * Yes on min sleep, which means
                           * we cannot be awoken.
                           */
                          hpts->overidden_sleep = tv.tv_usec;
                          tv.tv_usec = tcp_min_hptsi_time;
                          hpts->p_on_min_sleep = 1;
                  } else {
                          /* Clear the min sleep flag */
                          hpts->overidden_sleep = 0;
                          hpts->p_on_min_sleep = 0;
                  }
          }
          HPTS_MTX_ASSERT(hpts);
          hpts->p_hpts_active = 0;
  back_to_sleep:
          hpts->p_direct_wake = 0;
          sb = tvtosbt(tv);
          /* Store off to make visible the actual sleep time */
          hpts->sleeping = tv.tv_usec;
          callout_reset_sbt_on(&hpts->co, sb, 0,
                               hpts_timeout_swi, hpts, hpts->p_cpu,
                               (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
          NET_EPOCH_EXIT(et);
          mtx_unlock(&hpts->p_mtx);
  }
  
  #undef  timersub
  
  static int32_t
  hpts_count_level(struct cpu_group *cg)
  {
          int32_t count_l3, i;
  
          count_l3 = 0;
          if (cg->cg_level == CG_SHARE_L3)
                  count_l3++;
          /* Walk all the children looking for L3 */
          for (i = 0; i < cg->cg_children; i++) {
                  count_l3 += hpts_count_level(&cg->cg_child[i]);
          }
          return (count_l3);
  }
  
  static void
  hpts_gather_grps(struct cpu_group **grps, int32_t *at, int32_t max, struct cpu_group *cg)
  {
          int32_t idx, i;
  
          idx = *at;
          if (cg->cg_level == CG_SHARE_L3) {
                  grps[idx] = cg;
                  idx++;
                  if (idx == max) {
                          *at = idx;
                          return;
                  }
          }
          *at = idx;
          /* Walk all the children looking for L3 */
          for (i = 0; i < cg->cg_children; i++) {
                  hpts_gather_grps(grps, at, max, &cg->cg_child[i]);
          }
  }
  
  static void
  tcp_init_hptsi(void *st)
  {
          struct cpu_group *cpu_top;
          int32_t error __diagused;
          int32_t i, j, bound = 0, created = 0;
          size_t sz, asz;
          struct timeval tv;
          sbintime_t sb;
          struct tcp_hpts_entry *hpts;
          struct pcpu *pc;
          char unit[16];
          uint32_t ncpus = mp_ncpus ? mp_ncpus : MAXCPU;
          int count, domain;
  
  #ifdef SMP
          cpu_top = smp_topo();
  #else
          cpu_top = NULL;
  #endif
          tcp_pace.rp_num_hptss = ncpus;
          hpts_hopelessly_behind = counter_u64_alloc(M_WAITOK);
          hpts_loops = counter_u64_alloc(M_WAITOK);
          back_tosleep = counter_u64_alloc(M_WAITOK);
          combined_wheel_wrap = counter_u64_alloc(M_WAITOK);
          wheel_wrap = counter_u64_alloc(M_WAITOK);
          hpts_wake_timeout = counter_u64_alloc(M_WAITOK);
          hpts_direct_awakening = counter_u64_alloc(M_WAITOK);
          hpts_back_tosleep = counter_u64_alloc(M_WAITOK);
          hpts_direct_call = counter_u64_alloc(M_WAITOK);
          cpu_uses_flowid = counter_u64_alloc(M_WAITOK);
          cpu_uses_random = counter_u64_alloc(M_WAITOK);
  
          sz = (tcp_pace.rp_num_hptss * sizeof(struct tcp_hpts_entry *));
          tcp_pace.rp_ent = malloc(sz, M_TCPHPTS, M_WAITOK | M_ZERO);
          sz = (sizeof(uint32_t) * tcp_pace.rp_num_hptss);
          cts_last_ran = malloc(sz, M_TCPHPTS, M_WAITOK);
          tcp_pace.grp_cnt = 0;
          if (cpu_top == NULL) {
                  tcp_pace.grp_cnt = 1;
          } else {
                  /* Find out how many cache level 3 domains we have */
                  count = 0;
                  tcp_pace.grp_cnt = hpts_count_level(cpu_top);
                  if (tcp_pace.grp_cnt == 0) {
                          tcp_pace.grp_cnt = 1;
                  }
                  sz = (tcp_pace.grp_cnt * sizeof(struct cpu_group *));
                  tcp_pace.grps = malloc(sz, M_TCPHPTS, M_WAITOK);
                  /* Now populate the groups */
                  if (tcp_pace.grp_cnt == 1) {
                          /*
                           * All we need is the top level all cpu's are in
                           * the same cache so when we use grp[0]->cg_mask
                           * with the cg_first <-> cg_last it will include
                           * all cpu's in it. The level here is probably
                           * zero which is ok.
                           */
                          tcp_pace.grps[0] = cpu_top;
                  } else {
                          /*
                           * Here we must find all the level three cache domains
                           * and setup our pointers to them.
                           */
                          count = 0;
                          hpts_gather_grps(tcp_pace.grps, &count, tcp_pace.grp_cnt, cpu_top);
                  }
          }
          asz = sizeof(struct hptsh) * NUM_OF_HPTSI_SLOTS;
          for (i = 0; i < tcp_pace.rp_num_hptss; i++) {
                  tcp_pace.rp_ent[i] = malloc(sizeof(struct tcp_hpts_entry),
                      M_TCPHPTS, M_WAITOK | M_ZERO);
                  tcp_pace.rp_ent[i]->p_hptss = malloc(asz, M_TCPHPTS, M_WAITOK);
                  hpts = tcp_pace.rp_ent[i];
                  /*
                   * Init all the hpts structures that are not specifically
                   * zero'd by the allocations. Also lets attach them to the
                   * appropriate sysctl block as well.
                   */
                  mtx_init(&hpts->p_mtx, "tcp_hpts_lck",
                      "hpts", MTX_DEF | MTX_DUPOK);
                  for (j = 0; j < NUM_OF_HPTSI_SLOTS; j++) {
                          TAILQ_INIT(&hpts->p_hptss[j].head);
                          hpts->p_hptss[j].count = 0;
                          hpts->p_hptss[j].gencnt = 0;
                  }
                  sysctl_ctx_init(&hpts->hpts_ctx);
                  sprintf(unit, "%d", i);
                  hpts->hpts_root = SYSCTL_ADD_NODE(&hpts->hpts_ctx,
                      SYSCTL_STATIC_CHILDREN(_net_inet_tcp_hpts),
                      OID_AUTO,
                      unit,
                      CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                      "");
                  SYSCTL_ADD_INT(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "out_qcnt", CTLFLAG_RD,
                      &hpts->p_on_queue_cnt, 0,
                      "Count TCB's awaiting output processing");
                  SYSCTL_ADD_U16(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "active", CTLFLAG_RD,
                      &hpts->p_hpts_active, 0,
                      "Is the hpts active");
                  SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "curslot", CTLFLAG_RD,
                      &hpts->p_cur_slot, 0,
                      "What the current running pacers goal");
                  SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "runtick", CTLFLAG_RD,
                      &hpts->p_runningslot, 0,
                      "What the running pacers current slot is");
                  SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "curtick", CTLFLAG_RD,
                      &hpts->p_curtick, 0,
                      "What the running pacers last tick mapped to the wheel was");
                  SYSCTL_ADD_UINT(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "lastran", CTLFLAG_RD,
                      &cts_last_ran[i], 0,
                      "The last usec tick that this hpts ran");
                  SYSCTL_ADD_LONG(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "cur_min_sleep", CTLFLAG_RD,
                      &hpts->p_mysleep.tv_usec,
                      "What the running pacers is using for p_mysleep.tv_usec");
                  SYSCTL_ADD_U64(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "now_sleeping", CTLFLAG_RD,
                      &hpts->sleeping, 0,
                      "What the running pacers is actually sleeping for");
                  SYSCTL_ADD_U64(&hpts->hpts_ctx,
                      SYSCTL_CHILDREN(hpts->hpts_root),
                      OID_AUTO, "syscall_cnt", CTLFLAG_RD,
                      &hpts->syscall_cnt, 0,
                      "How many times we had syscalls on this hpts");
  
                  hpts->p_hpts_sleep_time = hpts_sleep_max;
                  hpts->p_num = i;
                  hpts->p_curtick = tcp_gethptstick(&tv);
                  cts_last_ran[i] = tcp_tv_to_usectick(&tv);
                  hpts->p_prev_slot = hpts->p_cur_slot = tick_to_wheel(hpts->p_curtick);
                  hpts->p_cpu = 0xffff;
                  hpts->p_nxt_slot = hpts_slot(hpts->p_cur_slot, 1);
                  callout_init(&hpts->co, 1);
          }
          /* Don't try to bind to NUMA domains if we don't have any */
          if (vm_ndomains == 1 && tcp_bind_threads == 2)
                  tcp_bind_threads = 0;
  
          /*
           * Now lets start ithreads to handle the hptss.
           */
          for (i = 0; i < tcp_pace.rp_num_hptss; i++) {
                  hpts = tcp_pace.rp_ent[i];
                  hpts->p_cpu = i;
  
                  error = swi_add(&hpts->ie, "hpts",
                      tcp_hpts_thread, (void *)hpts,
                      SWI_NET, INTR_MPSAFE, &hpts->ie_cookie);
                  KASSERT(error == 0,
                          ("Can't add hpts:%p i:%d err:%d",
                           hpts, i, error));
                  created++;
                  hpts->p_mysleep.tv_sec = 0;
                  hpts->p_mysleep.tv_usec = tcp_min_hptsi_time;
                  if (tcp_bind_threads == 1) {
                          if (intr_event_bind(hpts->ie, i) == 0)
                                  bound++;
                  } else if (tcp_bind_threads == 2) {
                          /* Find the group for this CPU (i) and bind into it */
                          for (j = 0; j < tcp_pace.grp_cnt; j++) {
                                  if (CPU_ISSET(i, &tcp_pace.grps[j]->cg_mask)) {
                                          if (intr_event_bind_ithread_cpuset(hpts->ie,
                                                  &tcp_pace.grps[j]->cg_mask) == 0) {
                                                  bound++;
                                                  pc = pcpu_find(i);
                                                  domain = pc->pc_domain;
                                                  count = hpts_domains[domain].count;
                                                  hpts_domains[domain].cpu[count] = i;
                                                  hpts_domains[domain].count++;
                                                  break;
                                          }
                                  }
                          }
                  }
                  tv.tv_sec = 0;
                  tv.tv_usec = hpts->p_hpts_sleep_time * HPTS_TICKS_PER_SLOT;
                  hpts->sleeping = tv.tv_usec;
                  sb = tvtosbt(tv);
                  callout_reset_sbt_on(&hpts->co, sb, 0,
                                       hpts_timeout_swi, hpts, hpts->p_cpu,
                                       (C_DIRECT_EXEC | C_PREL(tcp_hpts_precision)));
          }
          /*
           * If we somehow have an empty domain, fall back to choosing
           * among all htps threads.
           */
          for (i = 0; i < vm_ndomains; i++) {
                  if (hpts_domains[i].count == 0) {
                          tcp_bind_threads = 0;
                          break;
                  }
          }
          printf("TCP Hpts created %d swi interrupt threads and bound %d to %s\n",
              created, bound,
              tcp_bind_threads == 2 ? "NUMA domains" : "cpus");
  #ifdef INVARIANTS
          printf("HPTS is in INVARIANT mode!!\n");
  #endif
  }
  
  SYSINIT(tcphptsi, SI_SUB_SOFTINTR, SI_ORDER_ANY, tcp_init_hptsi, NULL);
  MODULE_VERSION(tcphpts, 1);

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