Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_zeroidle.c
Version:
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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/5.3/sys/vm/vm_zeroidle.c 135018 2004-09-10 00:04:18Z scottl $"); 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 int zero_state; 80 81 static int 82 vm_page_zero_check(void) 83 { 84 85 if (!idlezero_enable) 86 return (0); 87 /* 88 * Attempt to maintain approximately 1/2 of our free pages in a 89 * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid 90 * generally zeroing a page when the system is near steady-state. 91 * Otherwise we might get 'flutter' during disk I/O / IPC or 92 * fast sleeps. We also do not want to be continuously zeroing 93 * pages because doing so may flush our L1 and L2 caches too much. 94 */ 95 if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) 96 return (0); 97 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 98 return (0); 99 return (1); 100 } 101 102 static int 103 vm_page_zero_idle(void) 104 { 105 static int free_rover; 106 vm_page_t m; 107 108 mtx_lock_spin(&vm_page_queue_free_mtx); 109 zero_state = 0; 110 m = vm_pageq_find(PQ_FREE, free_rover, FALSE); 111 if (m != NULL && (m->flags & PG_ZERO) == 0) { 112 vm_pageq_remove_nowakeup(m); 113 mtx_unlock_spin(&vm_page_queue_free_mtx); 114 pmap_zero_page_idle(m); 115 mtx_lock_spin(&vm_page_queue_free_mtx); 116 m->flags |= PG_ZERO; 117 vm_pageq_enqueue(PQ_FREE + m->pc, m); 118 ++vm_page_zero_count; 119 ++cnt_prezero; 120 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 121 zero_state = 1; 122 } 123 free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK; 124 mtx_unlock_spin(&vm_page_queue_free_mtx); 125 return (1); 126 } 127 128 /* Called by vm_page_free to hint that a new page is available. */ 129 void 130 vm_page_zero_idle_wakeup(void) 131 { 132 133 if (idlezero_enable && vm_page_zero_check()) 134 wakeup(&zero_state); 135 } 136 137 static void 138 vm_pagezero(void __unused *arg) 139 { 140 struct proc *p; 141 struct rtprio rtp; 142 struct thread *td; 143 int pages, pri; 144 145 td = curthread; 146 p = td->td_proc; 147 rtp.prio = RTP_PRIO_MAX; 148 rtp.type = RTP_PRIO_IDLE; 149 pages = 0; 150 mtx_lock_spin(&sched_lock); 151 rtp_to_pri(&rtp, td->td_ksegrp); 152 pri = td->td_priority; 153 mtx_unlock_spin(&sched_lock); 154 idlezero_enable = idlezero_enable_default; 155 156 for (;;) { 157 if (vm_page_zero_check()) { 158 pages += vm_page_zero_idle(); 159 #ifndef PREEMPTION 160 if (pages > idlezero_maxrun || sched_runnable()) { 161 mtx_lock_spin(&sched_lock); 162 mi_switch(SW_VOL, NULL); 163 mtx_unlock_spin(&sched_lock); 164 pages = 0; 165 } 166 #endif 167 } else { 168 tsleep(&zero_state, pri, "pgzero", hz * 300); 169 pages = 0; 170 } 171 } 172 } 173 174 static struct proc *pagezero_proc; 175 176 static void 177 pagezero_start(void __unused *arg) 178 { 179 int error; 180 181 error = kthread_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0, 182 "pagezero"); 183 if (error) 184 panic("pagezero_start: error %d\n", error); 185 /* 186 * We're an idle task, don't count us in the load. 187 */ 188 PROC_LOCK(pagezero_proc); 189 pagezero_proc->p_flag |= P_NOLOAD; 190 PROC_UNLOCK(pagezero_proc); 191 mtx_lock_spin(&sched_lock); 192 setrunqueue(FIRST_THREAD_IN_PROC(pagezero_proc), SRQ_BORING); 193 mtx_unlock_spin(&sched_lock); 194 } 195 SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL)
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