vm_zeroidle.c

Version: - FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10

    1 /*-
    2  * Copyright (c) 1994 John Dyson
    3  * Copyright (c) 2001 Matt Dillon
    4  *
    5  * All Rights Reserved.
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 4. Neither the name of the University nor the names of its contributors
   15  *    may be used to endorse or promote products derived from this software
   16  *    without specific prior written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
   19  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
   24  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   25  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   26  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   27  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   28  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   29  *
   30  *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
   31  *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
   32  * from: FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon
   33  */
   34 
   35 #include <sys/cdefs.h>
   36 __FBSDID("$FreeBSD: releng/5.4/sys/vm/vm_zeroidle.c 142302 2005-02-23 15:03:56Z ssouhlal $");
   37 
   38 #include <opt_sched.h>
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/kernel.h>
   43 #include <sys/proc.h>
   44 #include <sys/resourcevar.h>
   45 #include <sys/vmmeter.h>
   46 #include <sys/lock.h>
   47 #include <sys/mutex.h>
   48 #include <sys/sched.h>
   49 #include <sys/sysctl.h>
   50 #include <sys/kthread.h>
   51 #include <sys/unistd.h>
   52 
   53 #include <vm/vm.h>
   54 #include <vm/vm_page.h>
   55 
   56 SYSCTL_DECL(_vm_stats_misc);
   57 
   58 static int cnt_prezero;
   59 SYSCTL_INT(_vm_stats_misc, OID_AUTO, cnt_prezero, CTLFLAG_RD,
   60     &cnt_prezero, 0, "");
   61 
   62 static int idlezero_enable_default = 1;
   63 TUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default);
   64 /* Defer setting the enable flag until the kthread is running. */
   65 static int idlezero_enable = 0;
   66 SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, "");
   67 
   68 static int idlezero_maxrun = 16;
   69 SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, "");
   70 TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun);
   71 
   72 /*
   73  * Implement the pre-zeroed page mechanism.
   74  */
   75 
   76 #define ZIDLE_LO(v)     ((v) * 2 / 3)
   77 #define ZIDLE_HI(v)     ((v) * 4 / 5)
   78 
   79 static boolean_t wakeup_needed = FALSE;
   80 static int zero_state;
   81 
   82 static int
   83 vm_page_zero_check(void)
   84 {
   85 
   86         if (!idlezero_enable)
   87                 return (0);
   88         /*
   89          * Attempt to maintain approximately 1/2 of our free pages in a
   90          * PG_ZERO'd state.   Add some hysteresis to (attempt to) avoid
   91          * generally zeroing a page when the system is near steady-state.
   92          * Otherwise we might get 'flutter' during disk I/O / IPC or 
   93          * fast sleeps.  We also do not want to be continuously zeroing
   94          * pages because doing so may flush our L1 and L2 caches too much.
   95          */
   96         if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count))
   97                 return (0);
   98         if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
   99                 return (0);
  100         return (1);
  101 }
  102 
  103 static int
  104 vm_page_zero_idle(void)
  105 {
  106         static int free_rover;
  107         vm_page_t m;
  108 
  109         mtx_lock_spin(&vm_page_queue_free_mtx);
  110         zero_state = 0;
  111         m = vm_pageq_find(PQ_FREE, free_rover, FALSE);
  112         if (m != NULL && (m->flags & PG_ZERO) == 0) {
  113                 vm_pageq_remove_nowakeup(m);
  114                 mtx_unlock_spin(&vm_page_queue_free_mtx);
  115                 pmap_zero_page_idle(m);
  116                 mtx_lock_spin(&vm_page_queue_free_mtx);
  117                 m->flags |= PG_ZERO;
  118                 vm_pageq_enqueue(PQ_FREE + m->pc, m);
  119                 ++vm_page_zero_count;
  120                 ++cnt_prezero;
  121                 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
  122                         zero_state = 1;
  123         }
  124         free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
  125         mtx_unlock_spin(&vm_page_queue_free_mtx);
  126         return (1);
  127 }
  128 
  129 /* Called by vm_page_free to hint that a new page is available. */
  130 void
  131 vm_page_zero_idle_wakeup(void)
  132 {
  133 
  134         mtx_assert(&vm_page_queue_mtx, MA_OWNED);
  135         if (wakeup_needed && vm_page_zero_check()) {
  136                 wakeup_needed = FALSE;
  137                 wakeup(&zero_state);
  138         }
  139 }
  140 
  141 static void
  142 vm_pagezero(void __unused *arg)
  143 {
  144         struct thread *td;
  145 
  146         td = curthread;
  147         idlezero_enable = idlezero_enable_default;
  148 
  149         for (;;) {
  150                 if (vm_page_zero_check()) {
  151                         vm_page_zero_idle();
  152 #ifndef PREEMPTION
  153                         if (sched_runnable()) {
  154                                 mtx_lock_spin(&sched_lock);
  155                                 mi_switch(SW_VOL, NULL);
  156                                 mtx_unlock_spin(&sched_lock);
  157                         }
  158 #endif
  159                 } else {
  160                         vm_page_lock_queues();
  161                         wakeup_needed = TRUE;
  162                         msleep(&zero_state, &vm_page_queue_mtx,
  163                             PDROP | td->td_priority, "pgzero", hz * 300);
  164                 }
  165         }
  166 }
  167 
  168 static struct proc *pagezero_proc;
  169 
  170 static void
  171 pagezero_start(void __unused *arg)
  172 {
  173         int error;
  174         struct thread *td;
  175 
  176         error = kthread_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0,
  177             "pagezero");
  178         if (error)
  179                 panic("pagezero_start: error %d\n", error);
  180         /*
  181          * We're an idle task, don't count us in the load.
  182          */
  183         PROC_LOCK(pagezero_proc);
  184         pagezero_proc->p_flag |= P_NOLOAD;
  185         PROC_UNLOCK(pagezero_proc);
  186         mtx_lock_spin(&sched_lock);
  187         td = FIRST_THREAD_IN_PROC(pagezero_proc);
  188         setrunqueue(td, SRQ_BORING);
  189         td->td_ksegrp->kg_user_pri = PRI_MAX_IDLE;
  190         sched_class(td->td_ksegrp, PRI_IDLE);
  191         sched_prio(td, PRI_MAX_IDLE);
  192         mtx_unlock_spin(&sched_lock);
  193 }
  194 SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL)

Cache object: 050eaab2ec0440d3965c757100e2ca7f

[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.

FreeBSD/Linux Kernel Cross Reference sys/vm/vm_zeroidle.c

FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_zeroidle.c