/*- * Copyright (c) 1994 John Dyson * Copyright (c) 2001 Matt Dillon * * All Rights Reserved. * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * from: @(#)vm_machdep.c 7.3 (Berkeley) 5/13/91 * Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$ * from: FreeBSD: .../i386/vm_machdep.c,v 1.165 2001/07/04 23:27:04 dillon */ #include __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static int idlezero_enable_default = 0; TUNABLE_INT("vm.idlezero_enable", &idlezero_enable_default); /* Defer setting the enable flag until the kthread is running. */ static int idlezero_enable = 0; SYSCTL_INT(_vm, OID_AUTO, idlezero_enable, CTLFLAG_RW, &idlezero_enable, 0, "Allow the kernel to use idle cpu cycles to zero-out pages"); /* * Implement the pre-zeroed page mechanism. */ #define ZIDLE_LO(v) ((v) * 2 / 3) #define ZIDLE_HI(v) ((v) * 4 / 5) static boolean_t wakeup_needed = FALSE; static int zero_state; static int vm_page_zero_check(void) { if (!idlezero_enable) return (0); /* * Attempt to maintain approximately 1/2 of our free pages in a * PG_ZERO'd state. Add some hysteresis to (attempt to) avoid * generally zeroing a page when the system is near steady-state. * Otherwise we might get 'flutter' during disk I/O / IPC or * fast sleeps. We also do not want to be continuously zeroing * pages because doing so may flush our L1 and L2 caches too much. */ if (zero_state && vm_page_zero_count >= ZIDLE_LO(cnt.v_free_count)) return (0); if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) return (0); return (1); } static void vm_page_zero_idle(void) { mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); zero_state = 0; if (vm_phys_zero_pages_idle()) { if (vm_page_zero_count >= ZIDLE_HI(cnt.v_free_count)) zero_state = 1; } } /* Called by vm_page_free to hint that a new page is available. */ void vm_page_zero_idle_wakeup(void) { mtx_assert(&vm_page_queue_free_mtx, MA_OWNED); if (wakeup_needed && vm_page_zero_check()) { wakeup_needed = FALSE; wakeup(&zero_state); } } static void vm_pagezero(void __unused *arg) { idlezero_enable = idlezero_enable_default; mtx_lock(&vm_page_queue_free_mtx); for (;;) { if (vm_page_zero_check()) { vm_page_zero_idle(); #ifndef PREEMPTION if (sched_runnable()) { thread_lock(curthread); mi_switch(SW_VOL | SWT_IDLE, NULL); thread_unlock(curthread); } #endif } else { wakeup_needed = TRUE; msleep(&zero_state, &vm_page_queue_free_mtx, 0, "pgzero", hz * 300); } } } static struct proc *pagezero_proc; static void pagezero_start(void __unused *arg) { int error; struct thread *td; error = kproc_create(vm_pagezero, NULL, &pagezero_proc, RFSTOPPED, 0, "pagezero"); if (error) panic("pagezero_start: error %d\n", error); /* * We're an idle task, don't count us in the load. */ PROC_LOCK(pagezero_proc); pagezero_proc->p_flag |= P_NOLOAD; PROC_UNLOCK(pagezero_proc); td = FIRST_THREAD_IN_PROC(pagezero_proc); thread_lock(td); sched_class(td, PRI_IDLE); sched_prio(td, PRI_MAX_IDLE); sched_add(td, SRQ_BORING); thread_unlock(td); } SYSINIT(pagezero, SI_SUB_KTHREAD_VM, SI_ORDER_ANY, pagezero_start, NULL);