vm_zeroidle.c

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    1 /*
    2  * (MPSAFE)
    3  *
    4  * Copyright (c) 1994 John Dyson
    5  * Copyright (c) 2001 Matt Dillon
    6  * Copyright (c) 2010 The DragonFly Project
    7  *
    8  * All Rights Reserved.
    9  *
   10  * This code is derived from software contributed to The DragonFly Project
   11  * by Venkatesh Srinivas <me@endeavour.zapto.org>
   12  *
   13  * Redistribution and use in source and binary forms, with or without
   14  * modification, are permitted provided that the following conditions
   15  * are met:
   16  * 1. Redistributions of source code must retain the above copyright
   17  *    notice, this list of conditions and the following disclaimer.
   18  * 2. Redistributions in binary form must reproduce the above copyright
   19  *    notice, this list of conditions and the following disclaimer in the
   20  *    documentation and/or other materials provided with the distribution.
   21  * 3. Neither the name of the University nor the names of its contributors
   22  *    may be used to endorse or promote products derived from this software
   23  *    without specific prior written permission.
   24  *
   25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
   26  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   27  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   29  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
   31  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   33  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   34  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   35  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   36  *
   37  *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
   38  *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
   39  * from FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon
   40  */
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/kernel.h>
   45 #include <sys/proc.h>
   46 #include <sys/vmmeter.h>
   47 #include <sys/sched.h>
   48 #include <sys/sysctl.h>
   49 #include <sys/thread.h>
   50 #include <sys/kthread.h>
   51 #include <sys/unistd.h>
   52 #include <vm/vm.h>
   53 #include <vm/vm_page.h>
   54 #include <cpu/lwbuf.h>
   55 
   56 #include <sys/thread2.h>
   57 #include <vm/vm_page2.h>
   58 
   59 /*
   60  * Implement the pre-zeroed page mechanism.
   61  */
   62 #define ZIDLE_LO(v)     ((v) * 2 / 3)
   63 #define ZIDLE_HI(v)     ((v) * 4 / 5)
   64 
   65 /* Number of bytes to zero between reschedule checks */
   66 #define IDLEZERO_RUN    (64)
   67 
   68 /* Maximum number of pages per second to zero */
   69 #define NPAGES_RUN      (20000)
   70 
   71 static int idlezero_enable = 1;
   72 TUNABLE_INT("vm.idlezero_enable", &idlezero_enable);
   73 SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0,
   74            "Allow the kernel to use idle CPU cycles to zero pages");
   75 static int idlezero_rate = NPAGES_RUN;
   76 SYSCTL_INT(_vm, OID_AUTO, idlezero_rate, CTLFLAG_RW, &idlezero_rate, 0,
   77            "Maximum pages per second to zero");
   78 static int idlezero_nocache = -1;
   79 SYSCTL_INT(_vm, OID_AUTO, idlezero_nocache, CTLFLAG_RW, &idlezero_nocache, 0,
   80            "Maximum pages per second to zero");
   81 
   82 static int idlezero_count = 0;
   83 SYSCTL_INT(_vm, OID_AUTO, idlezero_count, CTLFLAG_RD, &idlezero_count, 0,
   84            "The number of physical pages prezeroed at idle time");
   85 
   86 enum zeroidle_state {
   87         STATE_IDLE,
   88         STATE_GET_PAGE,
   89         STATE_ZERO_PAGE,
   90         STATE_RELEASE_PAGE
   91 };
   92 
   93 #define DEFAULT_SLEEP_TIME      (hz / 10)
   94 #define LONG_SLEEP_TIME         (hz * 10)
   95 
   96 static int zero_state;
   97 
   98 /*
   99  * Attempt to maintain approximately 1/2 of our free pages in a
  100  * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid
  101  * generally zeroing a page when the system is near steady-state.
  102  * Otherwise we might get 'flutter' during disk I/O / IPC or
  103  * fast sleeps. We also do not want to be continuously zeroing
  104  * pages because doing so may flush our L1 and L2 caches too much.
  105  *
  106  * Returns non-zero if pages should be zerod.
  107  */
  108 static int
  109 vm_page_zero_check(void)
  110 {
  111         if (idlezero_enable == 0)
  112                 return (0);
  113         if (zero_state == 0) {
  114                 /*
  115                  * Wait for the count to fall to LO before starting
  116                  * to zero pages.
  117                  */
  118                 if (vm_page_zero_count <= ZIDLE_LO(vmstats.v_free_count))
  119                         zero_state = 1;
  120         } else {
  121                 /*
  122                  * Once we are zeroing pages wait for the count to
  123                  * increase to HI before we stop zeroing pages.
  124                  */
  125                 if (vm_page_zero_count >= ZIDLE_HI(vmstats.v_free_count))
  126                         zero_state = 0;
  127         }
  128         return (zero_state);
  129 }
  130 
  131 /*
  132  * vm_pagezero should sleep for a longer time when idlezero is disabled or
  133  * when there is an excess of zeroed pages.
  134  */
  135 static int
  136 vm_page_zero_time(void)
  137 {
  138         if (idlezero_enable == 0)
  139                 return (LONG_SLEEP_TIME);
  140         if (vm_page_zero_count >= ZIDLE_HI(vmstats.v_free_count))
  141                 return (LONG_SLEEP_TIME);
  142         return (DEFAULT_SLEEP_TIME);
  143 }
  144 
  145 /*
  146  * MPSAFE thread
  147  */
  148 static void
  149 vm_pagezero(void __unused *arg)
  150 {
  151         vm_page_t m = NULL;
  152         struct lwbuf *lwb = NULL;
  153         struct lwbuf lwb_cache;
  154         enum zeroidle_state state = STATE_IDLE;
  155         char *pg = NULL;
  156         int npages = 0;
  157         int sleep_time; 
  158         int i = 0;
  159 
  160         /*
  161          * Adjust thread parameters before entering our loop.  The thread
  162          * is started with the MP lock held and with normal kernel thread
  163          * priority.
  164          *
  165          * Also put us on the last cpu for now.
  166          *
  167          * For now leave the MP lock held, the VM routines cannot be called
  168          * with it released until tokenization is finished.
  169          */
  170         lwkt_setpri_self(TDPRI_IDLE_WORK);
  171         lwkt_setcpu_self(globaldata_find(ncpus - 1));
  172         sleep_time = DEFAULT_SLEEP_TIME;
  173 
  174         /*
  175          * Loop forever
  176          */
  177         for (;;) {
  178                 switch(state) {
  179                 case STATE_IDLE:
  180                         /*
  181                          * Wait for work.
  182                          */
  183                         tsleep(&zero_state, 0, "pgzero", sleep_time);
  184                         if (vm_page_zero_check())
  185                                 npages = idlezero_rate / 10;
  186                         sleep_time = vm_page_zero_time();
  187                         if (npages)
  188                                 state = STATE_GET_PAGE; /* Fallthrough */
  189                         break;
  190                 case STATE_GET_PAGE:
  191                         /*
  192                          * Acquire page to zero
  193                          */
  194                         if (--npages == 0) {
  195                                 state = STATE_IDLE;
  196                         } else {
  197                                 m = vm_page_free_fromq_fast();
  198                                 if (m == NULL) {
  199                                         state = STATE_IDLE;
  200                                 } else {
  201                                         state = STATE_ZERO_PAGE;
  202                                         lwb = lwbuf_alloc(m, &lwb_cache);
  203                                         pg = (char *)lwbuf_kva(lwb);
  204                                         i = 0;
  205                                 }
  206                         }
  207                         break;
  208                 case STATE_ZERO_PAGE:
  209                         /*
  210                          * Zero-out the page
  211                          */
  212                         while (i < PAGE_SIZE) {
  213                                 if (idlezero_nocache == 1)
  214                                         bzeront(&pg[i], IDLEZERO_RUN);
  215                                 else
  216                                         bzero(&pg[i], IDLEZERO_RUN);
  217                                 i += IDLEZERO_RUN;
  218                                 lwkt_yield();
  219                         }
  220                         state = STATE_RELEASE_PAGE;
  221                         break;
  222                 case STATE_RELEASE_PAGE:
  223                         lwbuf_free(lwb);
  224                         vm_page_flag_set(m, PG_ZERO);
  225                         vm_page_free_toq(m);
  226                         state = STATE_GET_PAGE;
  227                         ++idlezero_count;
  228                         break;
  229                 }
  230                 lwkt_yield();
  231         }
  232 }
  233 
  234 static void
  235 pagezero_start(void __unused *arg)
  236 {
  237         int error;
  238         struct thread *td;
  239 
  240         if (idlezero_nocache < 0 && (cpu_mi_feature & CPU_MI_BZERONT))
  241                 idlezero_nocache = 1;
  242 
  243         error = kthread_create(vm_pagezero, NULL, &td, "pagezero");
  244         if (error)
  245                 panic("pagezero_start: error %d", error);
  246 }
  247 
  248 SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL);

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

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