163 lines
4.7 KiB
C
163 lines
4.7 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.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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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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* from: FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <opt_sched.h>
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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/vmmeter.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/sched.h>
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#include <sys/sysctl.h>
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#include <sys/kthread.h>
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#include <sys/unistd.h>
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#include <vm/vm.h>
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#include <vm/vm_param.h>
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#include <vm/vm_page.h>
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#include <vm/vm_phys.h>
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static int idlezero_enable_default = 0;
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/* Defer setting the enable flag until the kthread is running. */
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static int idlezero_enable = 0;
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SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RWTUN, &idlezero_enable, 0,
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"Allow the kernel to use idle cpu cycles to zero-out pages");
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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 boolean_t wakeup_needed = FALSE;
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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(vm_cnt.v_free_count))
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return (0);
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if (vm_page_zero_count >= ZIDLE_HI(vm_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 void
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vm_page_zero_idle(void)
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{
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mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
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zero_state = 0;
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if (vm_phys_zero_pages_idle()) {
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if (vm_page_zero_count >= ZIDLE_HI(vm_cnt.v_free_count))
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zero_state = 1;
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}
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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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mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
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if (wakeup_needed && vm_page_zero_check()) {
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wakeup_needed = FALSE;
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wakeup(&zero_state);
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}
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}
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static void
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vm_pagezero(void __unused *arg)
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{
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idlezero_enable = idlezero_enable_default;
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mtx_lock(&vm_page_queue_free_mtx);
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for (;;) {
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if (vm_page_zero_check()) {
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vm_page_zero_idle();
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#ifndef PREEMPTION
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if (sched_runnable()) {
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thread_lock(curthread);
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mi_switch(SW_VOL | SWT_IDLE, NULL);
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thread_unlock(curthread);
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}
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#endif
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} else {
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wakeup_needed = TRUE;
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msleep(&zero_state, &vm_page_queue_free_mtx, 0,
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"pgzero", hz * 300);
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}
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}
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}
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static void
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pagezero_start(void __unused *arg)
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{
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int error;
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struct proc *p;
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struct thread *td;
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error = kproc_create(vm_pagezero, NULL, &p, RFSTOPPED, 0, "pagezero");
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if (error)
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panic("pagezero_start: error %d\n", error);
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td = FIRST_THREAD_IN_PROC(p);
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thread_lock(td);
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/* We're an idle task, don't count us in the load. */
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td->td_flags |= TDF_NOLOAD;
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sched_class(td, PRI_IDLE);
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sched_prio(td, PRI_MAX_IDLE);
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sched_add(td, SRQ_BORING);
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thread_unlock(td);
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}
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SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL);
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