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3516c025ff
on and off since John Dyson left his work-in-progress. It is off by default for now. sysctl vm.zeroidle_enable=1 to turn it on. There are some hacks here to deal with the present lack of preemption - we yield after doing a small number of pages since we wont preempt otherwise. This is basically Matt's algorithm [with hysteresis] with an idle process to call it in a similar way it used to be called from the idle loop. I cleaned up the includes a fair bit here too.
150 lines
3.5 KiB
C
150 lines
3.5 KiB
C
/*-
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* Copyright (c) 1994 John Dyson
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* Copyright (c) 2001 Matt Dillon
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*
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* All rights reserved. Terms for use and redistribution
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* are covered by the BSD Copyright as found in /usr/src/COPYRIGHT.
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*
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* from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91
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* Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/vmmeter.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/sysctl.h>
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#include <sys/kthread.h>
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#include <vm/vm.h>
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#include <vm/vm_page.h>
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SYSCTL_DECL(_vm_stats_misc);
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static int cnt_prezero;
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SYSCTL_INT(_vm_stats_misc, OID_AUTO,
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cnt_prezero, CTLFLAG_RD, &cnt_prezero, 0, "");
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static int idlezero_enable = 0;
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SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, "");
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TUNABLE_INT("vm.idlezero_enable", &idlezero_enable);
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static int idlezero_maxrun = 16;
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SYSCTL_INT(_vm, OID_AUTO, idlezero_maxrun, CTLFLAG_RW, &idlezero_maxrun, 0, "");
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TUNABLE_INT("vm.idlezero_maxrun", &idlezero_maxrun);
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/*
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* Implement the pre-zeroed page mechanism.
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*/
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#define ZIDLE_LO(v) ((v) * 2 / 3)
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#define ZIDLE_HI(v) ((v) * 4 / 5)
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static int zero_state;
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static int
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vm_page_zero_check(void)
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{
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if (!idlezero_enable)
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return 0;
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/*
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* Attempt to maintain approximately 1/2 of our free pages in a
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* PG_ZERO'd state. Add some hysteresis to (attempt to) avoid
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* generally zeroing a page when the system is near steady-state.
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* Otherwise we might get 'flutter' during disk I/O / IPC or
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* fast sleeps. We also do not want to be continuously zeroing
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* pages because doing so may flush our L1 and L2 caches too much.
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*/
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if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count))
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return 0;
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if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
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return 0;
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return 1;
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}
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static int
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vm_page_zero_idle(void)
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{
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static int free_rover;
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vm_page_t m;
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mtx_lock(&Giant);
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zero_state = 0;
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m = vm_pageq_find(PQ_FREE, free_rover, FALSE);
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if (m != NULL && (m->flags & PG_ZERO) == 0) {
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vm_page_queues[m->queue].lcnt--;
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TAILQ_REMOVE(&vm_page_queues[m->queue].pl, m, pageq);
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m->queue = PQ_NONE;
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/* maybe drop out of Giant here */
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pmap_zero_page(VM_PAGE_TO_PHYS(m));
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/* and return here */
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vm_page_flag_set(m, PG_ZERO);
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m->queue = PQ_FREE + m->pc;
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vm_page_queues[m->queue].lcnt++;
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TAILQ_INSERT_TAIL(&vm_page_queues[m->queue].pl, m,
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pageq);
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++vm_page_zero_count;
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++cnt_prezero;
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if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count))
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zero_state = 1;
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}
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free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
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mtx_unlock(&Giant);
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return 1;
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}
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/* Called by vm_page_free to hint that a new page is available */
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void
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vm_page_zero_idle_wakeup(void)
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{
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if (vm_page_zero_check())
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wakeup(&zero_state);
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}
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static void
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vm_pagezero(void)
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{
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struct proc *p = curproc;
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struct rtprio rtp;
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int pages = 0;
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rtp.prio = RTP_PRIO_MAX;
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rtp.type = RTP_PRIO_IDLE;
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PROC_LOCK(p);
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rtp_to_pri(&rtp, &p->p_pri);
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PROC_UNLOCK(p);
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for (;;) {
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if (vm_page_zero_check()) {
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pages += vm_page_zero_idle();
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if (pages > idlezero_maxrun) {
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mtx_lock_spin(&sched_lock);
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setrunqueue(p);
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p->p_stats->p_ru.ru_nvcsw++;
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mi_switch();
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mtx_unlock_spin(&sched_lock);
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pages = 0;
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}
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} else {
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tsleep(&zero_state, PPAUSE, "pgzero", hz * 300);
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pages = 0;
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}
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}
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}
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static struct proc *pagezero;
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static struct kproc_desc pagezero_kp = {
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"pagezero",
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vm_pagezero,
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&pagezero
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};
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SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, kproc_start, &pagezero_kp)
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