vm_zeroidle.c revision 116226
1/*- 2 * Copyright (c) 1994 John Dyson 3 * Copyright (c) 2001 Matt Dillon 4 * 5 * All rights reserved. Terms for use and redistribution 6 * are covered by the BSD Copyright as found in /usr/src/COPYRIGHT. 7 * 8 * from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91 9 * Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$ 10 */ 11 12#include <sys/cdefs.h> 13__FBSDID("$FreeBSD: head/sys/vm/vm_zeroidle.c 116226 2003-06-11 23:50:51Z obrien $"); 14 15#include <sys/param.h> 16#include <sys/systm.h> 17#include <sys/kernel.h> 18#include <sys/proc.h> 19#include <sys/resourcevar.h> 20#include <sys/vmmeter.h> 21#include <sys/lock.h> 22#include <sys/mutex.h> 23#include <sys/sched.h> 24#include <sys/sysctl.h> 25#include <sys/kthread.h> 26 27#include <vm/vm.h> 28#include <vm/vm_page.h> 29 30SYSCTL_DECL(_vm_stats_misc); 31 32static int cnt_prezero; 33SYSCTL_INT(_vm_stats_misc, OID_AUTO, 34 cnt_prezero, CTLFLAG_RD, &cnt_prezero, 0, ""); 35 36static int idlezero_enable = 1; 37SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, ""); 38TUNABLE_INT("vm.idlezero_enable", &idlezero_enable); 39 40static int idlezero_maxrun = 16; 41SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, ""); 42TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun); 43 44/* 45 * Implement the pre-zeroed page mechanism. 46 */ 47 48#define ZIDLE_LO(v) ((v) * 2 / 3) 49#define ZIDLE_HI(v) ((v) * 4 / 5) 50 51static int zero_state; 52 53static int 54vm_page_zero_check(void) 55{ 56 57 if (!idlezero_enable) 58 return 0; 59 /* 60 * Attempt to maintain approximately 1/2 of our free pages in a 61 * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid 62 * generally zeroing a page when the system is near steady-state. 63 * Otherwise we might get 'flutter' during disk I/O / IPC or 64 * fast sleeps. We also do not want to be continuously zeroing 65 * pages because doing so may flush our L1 and L2 caches too much. 66 */ 67 if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) 68 return 0; 69 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 70 return 0; 71 return 1; 72} 73 74static int 75vm_page_zero_idle(void) 76{ 77 static int free_rover; 78 vm_page_t m; 79 80 mtx_lock_spin(&vm_page_queue_free_mtx); 81 zero_state = 0; 82 m = vm_pageq_find(PQ_FREE, free_rover, FALSE); 83 if (m != NULL && (m->flags & PG_ZERO) == 0) { 84 vm_pageq_remove_nowakeup(m); 85 mtx_unlock_spin(&vm_page_queue_free_mtx); 86 pmap_zero_page_idle(m); 87 mtx_lock_spin(&vm_page_queue_free_mtx); 88 m->flags |= PG_ZERO; 89 vm_pageq_enqueue(PQ_FREE + m->pc, m); 90 ++vm_page_zero_count; 91 ++cnt_prezero; 92 if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) 93 zero_state = 1; 94 } 95 free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK; 96 mtx_unlock_spin(&vm_page_queue_free_mtx); 97 return 1; 98} 99 100 101/* Called by vm_page_free to hint that a new page is available */ 102void 103vm_page_zero_idle_wakeup(void) 104{ 105 106 if (idlezero_enable && vm_page_zero_check()) 107 wakeup(&zero_state); 108} 109 110static void 111vm_pagezero(void) 112{ 113 struct thread *td; 114 struct proc *p; 115 struct rtprio rtp; 116 int pages = 0; 117 int pri; 118 119 td = curthread; 120 p = td->td_proc; 121 rtp.prio = RTP_PRIO_MAX; 122 rtp.type = RTP_PRIO_IDLE; 123 mtx_lock_spin(&sched_lock); 124 rtp_to_pri(&rtp, td->td_ksegrp); 125 pri = td->td_priority; 126 mtx_unlock_spin(&sched_lock); 127 PROC_LOCK(p); 128 p->p_flag |= P_NOLOAD; 129 PROC_UNLOCK(p); 130 131 for (;;) { 132 if (vm_page_zero_check()) { 133 pages += vm_page_zero_idle(); 134 if (pages > idlezero_maxrun || sched_runnable()) { 135 mtx_lock_spin(&sched_lock); 136 td->td_proc->p_stats->p_ru.ru_nvcsw++; 137 mi_switch(); 138 mtx_unlock_spin(&sched_lock); 139 pages = 0; 140 } 141 } else { 142 tsleep(&zero_state, pri, "pgzero", hz * 300); 143 pages = 0; 144 } 145 } 146} 147 148static struct proc *pagezero_proc; 149static struct kproc_desc pagezero_kp = { 150 "pagezero", 151 vm_pagezero, 152 &pagezero_proc 153}; 154SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &pagezero_kp) 155