sys/vm/vm_zeroidle.c

   1 /*
   2  * Copyright (c) 1994 John Dyson
   3  * Copyright (c) 2001 Matt Dillon
   4  * Copyright (c) 2010 The DragonFly Project
   5  *
   6  * All Rights Reserved.
   7  *
   8  * This code is derived from software contributed to The DragonFly Project
   9  * by Venkatesh Srinivas <me@endeavour.zapto.org>
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
  24  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  25  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  27  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  29  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  30  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  31  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  32  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  33  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  34  *
  35  *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
  36  *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
  37  * from FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon
  38  *
  39  * $Id: vm_zeroidle.c,v 1.3 2010/05/12 04:50:45 sv5679 Exp $
  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/thread2.h>
  51 #include <sys/kthread.h>
  52 #include <sys/mplock2.h>
  53 #include <sys/unistd.h>
  54 #include <vm/vm.h>
  55 #include <vm/vm_page.h>
  56 #include <cpu/lwbuf.h>
  57
  58 /*
  59  * Implement the pre-zeroed page mechanism.
  60  */
  61 #define ZIDLE_LO(v)     ((v) * 2 / 3)
  62 #define ZIDLE_HI(v)     ((v) * 4 / 5)
  63
  64 /* Number of bytes to zero between reschedule checks */
  65 #define IDLEZERO_RUN    (32)
  66
  67 /* Maximum number of pages per second to zero */
  68 #define NPAGES_RUN      (20000)
  69
  70
  71 static int idlezero_enable = 0;
  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 = 0;
  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 static int zero_state;
  94
  95 /*
  96  * Attempt to maintain approximately 1/2 of our free pages in a
  97  * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid
  98  * generally zeroing a page when the system is near steady-state.
  99  * Otherwise we might get 'flutter' during disk I/O / IPC or
 100  * fast sleeps. We also do not want to be continuously zeroing
 101  * pages because doing so may flush our L1 and L2 caches too much.
 102  */
 103 static int
 104 vm_page_zero_check(void)
 105 {
 106         if (idlezero_enable == 0)
 107                 return (0);
 108         if (zero_state && vm_page_zero_count >= ZIDLE_LO(vmstats.v_free_count))
 109                 return (0);
 110         if (vm_page_zero_count >= ZIDLE_HI(vmstats.v_free_count))
 111                 return (0);
 112         return (1);
 113 }
 114
 115 static void
 116 vm_pagezero(void __unused *arg)
 117 {
 118         vm_page_t m = NULL;
 119         struct lwbuf *buf = NULL;
 120         enum zeroidle_state state = STATE_IDLE;
 121         char *pg = NULL;
 122         int npages = 0;
 123         int i = 0;
 124
 125         /*
 126          * Adjust thread parameters before entering our loop.  The thread
 127          * is started with the MP lock held and with normal kernel thread
 128          * priority.
 129          *
 130          * Also put us on the last cpu for now.
 131          */
 132         rel_mplock();
 133         lwkt_setpri_self(TDPRI_IDLE_WORK);
 134         lwkt_setcpu_self(globaldata_find(ncpus - 1));
 135
 136         /*
 137          * Loop forever
 138          */
 139         for (;;) {
 140                 switch(state) {
 141                 case STATE_IDLE:
 142                         /*
 143                          * Wait for work.
 144                          */
 145                         tsleep(&zero_state, 0, "pgzero", hz / 10);
 146                         if (vm_page_zero_check())
 147                                 npages = idlezero_rate / 10;
 148                         if (npages)
 149                                 state = STATE_GET_PAGE; /* Fallthrough */
 150                         break;
 151                 case STATE_GET_PAGE:
 152                         /*
 153                          * Acquire page to zero
 154                          */
 155                         if (try_mplock() == 0) {
 156                                 state = STATE_IDLE;
 157                         } else if (--npages == 0) {
 158                                 state = STATE_IDLE;
 159                                 rel_mplock();
 160                         } else {
 161                                 m = vm_page_free_fromq_fast();
 162                                 if (m == NULL) {
 163                                         state = STATE_IDLE;
 164                                 } else {
 165                                         state = STATE_ZERO_PAGE;
 166                                         buf = lwbuf_alloc(m);
 167                                         pg = (char *)lwbuf_kva(buf);
 168                                         i = 0;
 169                                 }
 170                                 rel_mplock();
 171                         }
 172                         break;
 173                 case STATE_ZERO_PAGE:
 174                         /*
 175                          * Zero-out the page, stop immediately if a
 176                          * resched has been requested.
 177                          */
 178                         while (i < PAGE_SIZE) {
 179                                 if (lwkt_check_resched(curthread))
 180                                         break;
 181                                 if (idlezero_nocache == 1)
 182                                         bzeront(&pg[i], IDLEZERO_RUN);
 183                                 else
 184                                         bzero(&pg[i], IDLEZERO_RUN);
 185                                 i += IDLEZERO_RUN;
 186                         }
 187                         if (i == PAGE_SIZE)
 188                                 state = STATE_RELEASE_PAGE;
 189                         break;
 190                 case STATE_RELEASE_PAGE:
 191                         if (try_mplock()) {
 192                                 lwbuf_free(buf);
 193                                 vm_page_flag_set(m, PG_ZERO);
 194                                 vm_page_free_toq(m);
 195                                 state = STATE_GET_PAGE;
 196                                 ++idlezero_count;
 197                                 rel_mplock();
 198                         }
 199                         break;
 200                 }
 201                 lwkt_switch();
 202         }
 203 }
 204
 205 static void
 206 pagezero_start(void __unused *arg)
 207 {
 208         int error;
 209         struct thread *td;
 210
 211         error = kthread_create(vm_pagezero, NULL, &td, "pagezero");
 212         if (error)
 213                 panic("pagezero_start: error %d\n", error);
 214 }
 215
 216 SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL);