/*- * Copyright (c) 1991 Regents of the University of California. * All rights reserved. * Copyright (c) 1994 John S. Dyson * All rights reserved. * Copyright (c) 1994 David Greenman * All rights reserved. * Copyright (c) 2005 Yahoo! Technologies Norway AS * All rights reserved. * * This code is derived from software contributed to Berkeley by * The Mach Operating System project at Carnegie-Mellon University. * * 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 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 REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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_pageout.c 7.4 (Berkeley) 5/7/91 * * * Copyright (c) 1987, 1990 Carnegie-Mellon University. * All rights reserved. * * Authors: Avadis Tevanian, Jr., Michael Wayne Young * * Permission to use, copy, modify and distribute this software and * its documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. */ /* * The proverbial page-out daemon. */ #include __FBSDID("$FreeBSD$"); #include "opt_vm.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * System initialization */ /* the kernel process "vm_pageout"*/ static void vm_pageout(void); static int vm_pageout_clean(vm_page_t); static void vm_pageout_scan(int pass); struct proc *pageproc; static struct kproc_desc page_kp = { "pagedaemon", vm_pageout, &pageproc }; SYSINIT(pagedaemon, SI_SUB_KTHREAD_PAGE, SI_ORDER_FIRST, kproc_start, &page_kp); #if !defined(NO_SWAPPING) /* the kernel process "vm_daemon"*/ static void vm_daemon(void); static struct proc *vmproc; static struct kproc_desc vm_kp = { "vmdaemon", vm_daemon, &vmproc }; SYSINIT(vmdaemon, SI_SUB_KTHREAD_VM, SI_ORDER_FIRST, kproc_start, &vm_kp); #endif int vm_pages_needed; /* Event on which pageout daemon sleeps */ int vm_pageout_deficit; /* Estimated number of pages deficit */ int vm_pageout_pages_needed; /* flag saying that the pageout daemon needs pages */ #if !defined(NO_SWAPPING) static int vm_pageout_req_swapout; /* XXX */ static int vm_daemon_needed; static struct mtx vm_daemon_mtx; /* Allow for use by vm_pageout before vm_daemon is initialized. */ MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF); #endif static int vm_max_launder = 32; static int vm_pageout_stats_max=0, vm_pageout_stats_interval = 0; static int vm_pageout_full_stats_interval = 0; static int vm_pageout_algorithm=0; static int defer_swap_pageouts=0; static int disable_swap_pageouts=0; #if defined(NO_SWAPPING) static int vm_swap_enabled=0; static int vm_swap_idle_enabled=0; #else static int vm_swap_enabled=1; static int vm_swap_idle_enabled=0; #endif SYSCTL_INT(_vm, VM_PAGEOUT_ALGORITHM, pageout_algorithm, CTLFLAG_RW, &vm_pageout_algorithm, 0, "LRU page mgmt"); SYSCTL_INT(_vm, OID_AUTO, max_launder, CTLFLAG_RW, &vm_max_launder, 0, "Limit dirty flushes in pageout"); SYSCTL_INT(_vm, OID_AUTO, pageout_stats_max, CTLFLAG_RW, &vm_pageout_stats_max, 0, "Max pageout stats scan length"); SYSCTL_INT(_vm, OID_AUTO, pageout_full_stats_interval, CTLFLAG_RW, &vm_pageout_full_stats_interval, 0, "Interval for full stats scan"); SYSCTL_INT(_vm, OID_AUTO, pageout_stats_interval, CTLFLAG_RW, &vm_pageout_stats_interval, 0, "Interval for partial stats scan"); #if defined(NO_SWAPPING) SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RD, &vm_swap_enabled, 0, "Enable entire process swapout"); SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RD, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); #else SYSCTL_INT(_vm, VM_SWAPPING_ENABLED, swap_enabled, CTLFLAG_RW, &vm_swap_enabled, 0, "Enable entire process swapout"); SYSCTL_INT(_vm, OID_AUTO, swap_idle_enabled, CTLFLAG_RW, &vm_swap_idle_enabled, 0, "Allow swapout on idle criteria"); #endif SYSCTL_INT(_vm, OID_AUTO, defer_swapspace_pageouts, CTLFLAG_RW, &defer_swap_pageouts, 0, "Give preference to dirty pages in mem"); SYSCTL_INT(_vm, OID_AUTO, disable_swapspace_pageouts, CTLFLAG_RW, &disable_swap_pageouts, 0, "Disallow swapout of dirty pages"); static int pageout_lock_miss; SYSCTL_INT(_vm, OID_AUTO, pageout_lock_miss, CTLFLAG_RD, &pageout_lock_miss, 0, "vget() lock misses during pageout"); #define VM_PAGEOUT_PAGE_COUNT 16 int vm_pageout_page_count = VM_PAGEOUT_PAGE_COUNT; int vm_page_max_wired; /* XXX max # of wired pages system-wide */ SYSCTL_INT(_vm, OID_AUTO, max_wired, CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count"); #if !defined(NO_SWAPPING) static void vm_pageout_map_deactivate_pages(vm_map_t, long); static void vm_pageout_object_deactivate_pages(pmap_t, vm_object_t, long); static void vm_req_vmdaemon(int req); #endif static void vm_pageout_page_stats(void); /* * vm_pageout_fallback_object_lock: * * Lock vm object currently associated with `m'. VM_OBJECT_TRYLOCK is * known to have failed and page queue must be either PQ_ACTIVE or * PQ_INACTIVE. To avoid lock order violation, unlock the page queues * while locking the vm object. Use marker page to detect page queue * changes and maintain notion of next page on page queue. Return * TRUE if no changes were detected, FALSE otherwise. vm object is * locked on return. * * This function depends on both the lock portion of struct vm_object * and normal struct vm_page being type stable. */ boolean_t vm_pageout_fallback_object_lock(vm_page_t m, vm_page_t *next) { struct vm_page marker; boolean_t unchanged; u_short queue; vm_object_t object; /* * Initialize our marker */ bzero(&marker, sizeof(marker)); marker.flags = PG_FICTITIOUS | PG_MARKER; marker.oflags = VPO_BUSY; marker.queue = m->queue; marker.wire_count = 1; queue = m->queue; object = m->object; TAILQ_INSERT_AFTER(&vm_page_queues[queue].pl, m, &marker, pageq); vm_page_unlock_queues(); VM_OBJECT_LOCK(object); vm_page_lock_queues(); /* Page queue might have changed. */ *next = TAILQ_NEXT(&marker, pageq); unchanged = (m->queue == queue && m->object == object && &marker == TAILQ_NEXT(m, pageq)); TAILQ_REMOVE(&vm_page_queues[queue].pl, &marker, pageq); return (unchanged); } /* * vm_pageout_clean: * * Clean the page and remove it from the laundry. * * We set the busy bit to cause potential page faults on this page to * block. Note the careful timing, however, the busy bit isn't set till * late and we cannot do anything that will mess with the page. */ static int vm_pageout_clean(m) vm_page_t m; { vm_object_t object; vm_page_t mc[2*vm_pageout_page_count]; int pageout_count; int ib, is, page_base; vm_pindex_t pindex = m->pindex; mtx_assert(&vm_page_queue_mtx, MA_OWNED); VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); /* * It doesn't cost us anything to pageout OBJT_DEFAULT or OBJT_SWAP * with the new swapper, but we could have serious problems paging * out other object types if there is insufficient memory. * * Unfortunately, checking free memory here is far too late, so the * check has been moved up a procedural level. */ /* * Can't clean the page if it's busy or held. */ if ((m->hold_count != 0) || ((m->busy != 0) || (m->oflags & VPO_BUSY))) { return 0; } mc[vm_pageout_page_count] = m; pageout_count = 1; page_base = vm_pageout_page_count; ib = 1; is = 1; /* * Scan object for clusterable pages. * * We can cluster ONLY if: ->> the page is NOT * clean, wired, busy, held, or mapped into a * buffer, and one of the following: * 1) The page is inactive, or a seldom used * active page. * -or- * 2) we force the issue. * * During heavy mmap/modification loads the pageout * daemon can really fragment the underlying file * due to flushing pages out of order and not trying * align the clusters (which leave sporatic out-of-order * holes). To solve this problem we do the reverse scan * first and attempt to align our cluster, then do a * forward scan if room remains. */ object = m->object; more: while (ib && pageout_count < vm_pageout_page_count) { vm_page_t p; if (ib > pindex) { ib = 0; break; } if ((p = vm_page_lookup(object, pindex - ib)) == NULL) { ib = 0; break; } if ((p->oflags & VPO_BUSY) || p->busy) { ib = 0; break; } vm_page_test_dirty(p); if ((p->dirty & p->valid) == 0 || p->queue != PQ_INACTIVE || p->wire_count != 0 || /* may be held by buf cache */ p->hold_count != 0) { /* may be undergoing I/O */ ib = 0; break; } mc[--page_base] = p; ++pageout_count; ++ib; /* * alignment boundry, stop here and switch directions. Do * not clear ib. */ if ((pindex - (ib - 1)) % vm_pageout_page_count == 0) break; } while (pageout_count < vm_pageout_page_count && pindex + is < object->size) { vm_page_t p; if ((p = vm_page_lookup(object, pindex + is)) == NULL) break; if ((p->oflags & VPO_BUSY) || p->busy) { break; } vm_page_test_dirty(p); if ((p->dirty & p->valid) == 0 || p->queue != PQ_INACTIVE || p->wire_count != 0 || /* may be held by buf cache */ p->hold_count != 0) { /* may be undergoing I/O */ break; } mc[page_base + pageout_count] = p; ++pageout_count; ++is; } /* * If we exhausted our forward scan, continue with the reverse scan * when possible, even past a page boundry. This catches boundry * conditions. */ if (ib && pageout_count < vm_pageout_page_count) goto more; /* * we allow reads during pageouts... */ return (vm_pageout_flush(&mc[page_base], pageout_count, 0)); } /* * vm_pageout_flush() - launder the given pages * * The given pages are laundered. Note that we setup for the start of * I/O ( i.e. busy the page ), mark it read-only, and bump the object * reference count all in here rather then in the parent. If we want * the parent to do more sophisticated things we may have to change * the ordering. */ int vm_pageout_flush(vm_page_t *mc, int count, int flags) { vm_object_t object = mc[0]->object; int pageout_status[count]; int numpagedout = 0; int i; mtx_assert(&vm_page_queue_mtx, MA_OWNED); VM_OBJECT_LOCK_ASSERT(object, MA_OWNED); /* * Initiate I/O. Bump the vm_page_t->busy counter and * mark the pages read-only. * * We do not have to fixup the clean/dirty bits here... we can * allow the pager to do it after the I/O completes. * * NOTE! mc[i]->dirty may be partial or fragmented due to an * edge case with file fragments. */ for (i = 0; i < count; i++) { KASSERT(mc[i]->valid == VM_PAGE_BITS_ALL, ("vm_pageout_flush: partially invalid page %p index %d/%d", mc[i], i, count)); vm_page_io_start(mc[i]); pmap_remove_write(mc[i]); } vm_page_unlock_queues(); vm_object_pip_add(object, count); vm_pager_put_pages(object, mc, count, flags, pageout_status); vm_page_lock_queues(); for (i = 0; i < count; i++) { vm_page_t mt = mc[i]; KASSERT(pageout_status[i] == VM_PAGER_PEND || (mt->flags & PG_WRITEABLE) == 0, ("vm_pageout_flush: page %p is not write protected", mt)); switch (pageout_status[i]) { case VM_PAGER_OK: case VM_PAGER_PEND: numpagedout++; break; case VM_PAGER_BAD: /* * Page outside of range of object. Right now we * essentially lose the changes by pretending it * worked. */ vm_page_undirty(mt); break; case VM_PAGER_ERROR: case VM_PAGER_FAIL: /* * If page couldn't be paged out, then reactivate the * page so it doesn't clog the inactive list. (We * will try paging out it again later). */ vm_page_activate(mt); break; case VM_PAGER_AGAIN: break; } /* * If the operation is still going, leave the page busy to * block all other accesses. Also, leave the paging in * progress indicator set so that we don't attempt an object * collapse. */ if (pageout_status[i] != VM_PAGER_PEND) { vm_object_pip_wakeup(object); vm_page_io_finish(mt); if (vm_page_count_severe()) vm_page_try_to_cache(mt); } } return numpagedout; } #if !defined(NO_SWAPPING) /* * vm_pageout_object_deactivate_pages * * deactivate enough pages to satisfy the inactive target * requirements or if vm_page_proc_limit is set, then * deactivate all of the pages in the object and its * backing_objects. * * The object and map must be locked. */ static void vm_pageout_object_deactivate_pages(pmap, first_object, desired) pmap_t pmap; vm_object_t first_object; long desired; { vm_object_t backing_object, object; vm_page_t p, next; int actcount, rcount, remove_mode; VM_OBJECT_LOCK_ASSERT(first_object, MA_OWNED); if (first_object->type == OBJT_DEVICE || first_object->type == OBJT_PHYS) return; for (object = first_object;; object = backing_object) { if (pmap_resident_count(pmap) <= desired) goto unlock_return; if (object->paging_in_progress) goto unlock_return; remove_mode = 0; if (object->shadow_count > 1) remove_mode = 1; /* * scan the objects entire memory queue */ rcount = object->resident_page_count; p = TAILQ_FIRST(&object->memq); vm_page_lock_queues(); while (p && (rcount-- > 0)) { if (pmap_resident_count(pmap) <= desired) { vm_page_unlock_queues(); goto unlock_return; } next = TAILQ_NEXT(p, listq); cnt.v_pdpages++; if (p->wire_count != 0 || p->hold_count != 0 || p->busy != 0 || (p->oflags & VPO_BUSY) || (p->flags & PG_UNMANAGED) || !pmap_page_exists_quick(pmap, p)) { p = next; continue; } actcount = pmap_ts_referenced(p); if (actcount) { vm_page_flag_set(p, PG_REFERENCED); } else if (p->flags & PG_REFERENCED) { actcount = 1; } if ((p->queue != PQ_ACTIVE) && (p->flags & PG_REFERENCED)) { vm_page_activate(p); p->act_count += actcount; vm_page_flag_clear(p, PG_REFERENCED); } else if (p->queue == PQ_ACTIVE) { if ((p->flags & PG_REFERENCED) == 0) { p->act_count -= min(p->act_count, ACT_DECLINE); if (!remove_mode && (vm_pageout_algorithm || (p->act_count == 0))) { pmap_remove_all(p); vm_page_deactivate(p); } else { vm_page_requeue(p); } } else { vm_page_activate(p); vm_page_flag_clear(p, PG_REFERENCED); if (p->act_count < (ACT_MAX - ACT_ADVANCE)) p->act_count += ACT_ADVANCE; vm_page_requeue(p); } } else if (p->queue == PQ_INACTIVE) { pmap_remove_all(p); } p = next; } vm_page_unlock_queues(); if ((backing_object = object->backing_object) == NULL) goto unlock_return; VM_OBJECT_LOCK(backing_object); if (object != first_object) VM_OBJECT_UNLOCK(object); } unlock_return: if (object != first_object) VM_OBJECT_UNLOCK(object); } /* * deactivate some number of pages in a map, try to do it fairly, but * that is really hard to do. */ static void vm_pageout_map_deactivate_pages(map, desired) vm_map_t map; long desired; { vm_map_entry_t tmpe; vm_object_t obj, bigobj; int nothingwired; if (!vm_map_trylock(map)) return; bigobj = NULL; nothingwired = TRUE; /* * first, search out the biggest object, and try to free pages from * that. */ tmpe = map->header.next; while (tmpe != &map->header) { if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { obj = tmpe->object.vm_object; if (obj != NULL && VM_OBJECT_TRYLOCK(obj)) { if (obj->shadow_count <= 1 && (bigobj == NULL || bigobj->resident_page_count < obj->resident_page_count)) { if (bigobj != NULL) VM_OBJECT_UNLOCK(bigobj); bigobj = obj; } else VM_OBJECT_UNLOCK(obj); } } if (tmpe->wired_count > 0) nothingwired = FALSE; tmpe = tmpe->next; } if (bigobj != NULL) { vm_pageout_object_deactivate_pages(map->pmap, bigobj, desired); VM_OBJECT_UNLOCK(bigobj); } /* * Next, hunt around for other pages to deactivate. We actually * do this search sort of wrong -- .text first is not the best idea. */ tmpe = map->header.next; while (tmpe != &map->header) { if (pmap_resident_count(vm_map_pmap(map)) <= desired) break; if ((tmpe->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) { obj = tmpe->object.vm_object; if (obj != NULL) { VM_OBJECT_LOCK(obj); vm_pageout_object_deactivate_pages(map->pmap, obj, desired); VM_OBJECT_UNLOCK(obj); } } tmpe = tmpe->next; } /* * Remove all mappings if a process is swapped out, this will free page * table pages. */ if (desired == 0 && nothingwired) { pmap_remove(vm_map_pmap(map), vm_map_min(map), vm_map_max(map)); } vm_map_unlock(map); } #endif /* !defined(NO_SWAPPING) */ /* * vm_pageout_scan does the dirty work for the pageout daemon. */ static void vm_pageout_scan(int pass) { vm_page_t m, next; struct vm_page marker; int page_shortage, maxscan, pcount; int addl_page_shortage, addl_page_shortage_init; vm_object_t object; int actcount; int vnodes_skipped = 0; int maxlaunder; /* * Decrease registered cache sizes. */ EVENTHANDLER_INVOKE(vm_lowmem, 0); /* * We do this explicitly after the caches have been drained above. */ uma_reclaim(); addl_page_shortage_init = atomic_readandclear_int(&vm_pageout_deficit); /* * Calculate the number of pages we want to either free or move * to the cache. */ page_shortage = vm_paging_target() + addl_page_shortage_init; /* * Initialize our marker */ bzero(&marker, sizeof(marker)); marker.flags = PG_FICTITIOUS | PG_MARKER; marker.oflags = VPO_BUSY; marker.queue = PQ_INACTIVE; marker.wire_count = 1; /* * Start scanning the inactive queue for pages we can move to the * cache or free. The scan will stop when the target is reached or * we have scanned the entire inactive queue. Note that m->act_count * is not used to form decisions for the inactive queue, only for the * active queue. * * maxlaunder limits the number of dirty pages we flush per scan. * For most systems a smaller value (16 or 32) is more robust under * extreme memory and disk pressure because any unnecessary writes * to disk can result in extreme performance degredation. However, * systems with excessive dirty pages (especially when MAP_NOSYNC is * used) will die horribly with limited laundering. If the pageout * daemon cannot clean enough pages in the first pass, we let it go * all out in succeeding passes. */ if ((maxlaunder = vm_max_launder) <= 1) maxlaunder = 1; if (pass) maxlaunder = 10000; vm_page_lock_queues(); rescan0: addl_page_shortage = addl_page_shortage_init; maxscan = cnt.v_inactive_count; for (m = TAILQ_FIRST(&vm_page_queues[PQ_INACTIVE].pl); m != NULL && maxscan-- > 0 && page_shortage > 0; m = next) { cnt.v_pdpages++; if (VM_PAGE_GETQUEUE(m) != PQ_INACTIVE) { goto rescan0; } next = TAILQ_NEXT(m, pageq); object = m->object; /* * skip marker pages */ if (m->flags & PG_MARKER) continue; /* * A held page may be undergoing I/O, so skip it. */ if (m->hold_count) { vm_page_requeue(m); addl_page_shortage++; continue; } /* * Don't mess with busy pages, keep in the front of the * queue, most likely are being paged out. */ if (!VM_OBJECT_TRYLOCK(object) && (!vm_pageout_fallback_object_lock(m, &next) || m->hold_count != 0)) { VM_OBJECT_UNLOCK(object); addl_page_shortage++; continue; } if (m->busy || (m->oflags & VPO_BUSY)) { VM_OBJECT_UNLOCK(object); addl_page_shortage++; continue; } /* * If the object is not being used, we ignore previous * references. */ if (object->ref_count == 0) { vm_page_flag_clear(m, PG_REFERENCED); pmap_clear_reference(m); /* * Otherwise, if the page has been referenced while in the * inactive queue, we bump the "activation count" upwards, * making it less likely that the page will be added back to * the inactive queue prematurely again. Here we check the * page tables (or emulated bits, if any), given the upper * level VM system not knowing anything about existing * references. */ } else if (((m->flags & PG_REFERENCED) == 0) && (actcount = pmap_ts_referenced(m))) { vm_page_activate(m); VM_OBJECT_UNLOCK(object); m->act_count += (actcount + ACT_ADVANCE); continue; } /* * If the upper level VM system knows about any page * references, we activate the page. We also set the * "activation count" higher than normal so that we will less * likely place pages back onto the inactive queue again. */ if ((m->flags & PG_REFERENCED) != 0) { vm_page_flag_clear(m, PG_REFERENCED); actcount = pmap_ts_referenced(m); vm_page_activate(m); VM_OBJECT_UNLOCK(object); m->act_count += (actcount + ACT_ADVANCE + 1); continue; } /* * If the upper level VM system doesn't know anything about * the page being dirty, we have to check for it again. As * far as the VM code knows, any partially dirty pages are * fully dirty. */ if (m->dirty == 0 && !pmap_is_modified(m)) { /* * Avoid a race condition: Unless write access is * removed from the page, another processor could * modify it before all access is removed by the call * to vm_page_cache() below. If vm_page_cache() finds * that the page has been modified when it removes all * access, it panics because it cannot cache dirty * pages. In principle, we could eliminate just write * access here rather than all access. In the expected * case, when there are no last instant modifications * to the page, removing all access will be cheaper * overall. */ if ((m->flags & PG_WRITEABLE) != 0) pmap_remove_all(m); } else { vm_page_dirty(m); } if (m->valid == 0) { /* * Invalid pages can be easily freed */ vm_page_free(m); cnt.v_dfree++; --page_shortage; } else if (m->dirty == 0) { /* * Clean pages can be placed onto the cache queue. * This effectively frees them. */ vm_page_cache(m); --page_shortage; } else if ((m->flags & PG_WINATCFLS) == 0 && pass == 0) { /* * Dirty pages need to be paged out, but flushing * a page is extremely expensive verses freeing * a clean page. Rather then artificially limiting * the number of pages we can flush, we instead give * dirty pages extra priority on the inactive queue * by forcing them to be cycled through the queue * twice before being flushed, after which the * (now clean) page will cycle through once more * before being freed. This significantly extends * the thrash point for a heavily loaded machine. */ vm_page_flag_set(m, PG_WINATCFLS); vm_page_requeue(m); } else if (maxlaunder > 0) { /* * We always want to try to flush some dirty pages if * we encounter them, to keep the system stable. * Normally this number is small, but under extreme * pressure where there are insufficient clean pages * on the inactive queue, we may have to go all out. */ int swap_pageouts_ok, vfslocked = 0; struct vnode *vp = NULL; struct mount *mp = NULL; if ((object->type != OBJT_SWAP) && (object->type != OBJT_DEFAULT)) { swap_pageouts_ok = 1; } else { swap_pageouts_ok = !(defer_swap_pageouts || disable_swap_pageouts); swap_pageouts_ok |= (!disable_swap_pageouts && defer_swap_pageouts && vm_page_count_min()); } /* * We don't bother paging objects that are "dead". * Those objects are in a "rundown" state. */ if (!swap_pageouts_ok || (object->flags & OBJ_DEAD)) { VM_OBJECT_UNLOCK(object); vm_page_requeue(m); continue; } /* * Following operations may unlock * vm_page_queue_mtx, invalidating the 'next' * pointer. To prevent an inordinate number * of restarts we use our marker to remember * our place. * */ TAILQ_INSERT_AFTER(&vm_page_queues[PQ_INACTIVE].pl, m, &marker, pageq); /* * The object is already known NOT to be dead. It * is possible for the vget() to block the whole * pageout daemon, but the new low-memory handling * code should prevent it. * * The previous code skipped locked vnodes and, worse, * reordered pages in the queue. This results in * completely non-deterministic operation and, on a * busy system, can lead to extremely non-optimal * pageouts. For example, it can cause clean pages * to be freed and dirty pages to be moved to the end * of the queue. Since dirty pages are also moved to * the end of the queue once-cleaned, this gives * way too large a weighting to defering the freeing * of dirty pages. * * We can't wait forever for the vnode lock, we might * deadlock due to a vn_read() getting stuck in * vm_wait while holding this vnode. We skip the * vnode if we can't get it in a reasonable amount * of time. */ if (object->type == OBJT_VNODE) { vp = object->handle; if (vp->v_type == VREG && vn_start_write(vp, &mp, V_NOWAIT) != 0) { mp = NULL; ++pageout_lock_miss; if (object->flags & OBJ_MIGHTBEDIRTY) vnodes_skipped++; goto unlock_and_continue; } vm_page_unlock_queues(); vm_object_reference_locked(object); VM_OBJECT_UNLOCK(object); vfslocked = VFS_LOCK_GIANT(vp->v_mount); if (vget(vp, LK_EXCLUSIVE | LK_TIMELOCK, curthread)) { VM_OBJECT_LOCK(object); vm_page_lock_queues(); ++pageout_lock_miss; if (object->flags & OBJ_MIGHTBEDIRTY) vnodes_skipped++; vp = NULL; goto unlock_and_continue; } VM_OBJECT_LOCK(object); vm_page_lock_queues(); /* * The page might have been moved to another * queue during potential blocking in vget() * above. The page might have been freed and * reused for another vnode. */ if (VM_PAGE_GETQUEUE(m) != PQ_INACTIVE || m->object != object || TAILQ_NEXT(m, pageq) != &marker) { if (object->flags & OBJ_MIGHTBEDIRTY) vnodes_skipped++; goto unlock_and_continue; } /* * The page may have been busied during the * blocking in vget(). We don't move the * page back onto the end of the queue so that * statistics are more correct if we don't. */ if (m->busy || (m->oflags & VPO_BUSY)) { goto unlock_and_continue; } /* * If the page has become held it might * be undergoing I/O, so skip it */ if (m->hold_count) { vm_page_requeue(m); if (object->flags & OBJ_MIGHTBEDIRTY) vnodes_skipped++; goto unlock_and_continue; } } /* * If a page is dirty, then it is either being washed * (but not yet cleaned) or it is still in the * laundry. If it is still in the laundry, then we * start the cleaning operation. * * decrement page_shortage on success to account for * the (future) cleaned page. Otherwise we could wind * up laundering or cleaning too many pages. */ if (vm_pageout_clean(m) != 0) { --page_shortage; --maxlaunder; } unlock_and_continue: VM_OBJECT_UNLOCK(object); if (mp != NULL) { vm_page_unlock_queues(); if (vp != NULL) vput(vp); VFS_UNLOCK_GIANT(vfslocked); vm_object_deallocate(object); vn_finished_write(mp); vm_page_lock_queues(); } next = TAILQ_NEXT(&marker, pageq); TAILQ_REMOVE(&vm_page_queues[PQ_INACTIVE].pl, &marker, pageq); continue; } VM_OBJECT_UNLOCK(object); } /* * Compute the number of pages we want to try to move from the * active queue to the inactive queue. */ page_shortage = vm_paging_target() + cnt.v_inactive_target - cnt.v_inactive_count; page_shortage += addl_page_shortage; /* * Scan the active queue for things we can deactivate. We nominally * track the per-page activity counter and use it to locate * deactivation candidates. */ pcount = cnt.v_active_count; m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); while ((m != NULL) && (pcount-- > 0) && (page_shortage > 0)) { KASSERT(VM_PAGE_INQUEUE2(m, PQ_ACTIVE), ("vm_pageout_scan: page %p isn't active", m)); next = TAILQ_NEXT(m, pageq); object = m->object; if ((m->flags & PG_MARKER) != 0) { m = next; continue; } if (!VM_OBJECT_TRYLOCK(object) && !vm_pageout_fallback_object_lock(m, &next)) { VM_OBJECT_UNLOCK(object); m = next; continue; } /* * Don't deactivate pages that are busy. */ if ((m->busy != 0) || (m->oflags & VPO_BUSY) || (m->hold_count != 0)) { VM_OBJECT_UNLOCK(object); vm_page_requeue(m); m = next; continue; } /* * The count for pagedaemon pages is done after checking the * page for eligibility... */ cnt.v_pdpages++; /* * Check to see "how much" the page has been used. */ actcount = 0; if (object->ref_count != 0) { if (m->flags & PG_REFERENCED) { actcount += 1; } actcount += pmap_ts_referenced(m); if (actcount) { m->act_count += ACT_ADVANCE + actcount; if (m->act_count > ACT_MAX) m->act_count = ACT_MAX; } } /* * Since we have "tested" this bit, we need to clear it now. */ vm_page_flag_clear(m, PG_REFERENCED); /* * Only if an object is currently being used, do we use the * page activation count stats. */ if (actcount && (object->ref_count != 0)) { vm_page_requeue(m); } else { m->act_count -= min(m->act_count, ACT_DECLINE); if (vm_pageout_algorithm || object->ref_count == 0 || m->act_count == 0) { page_shortage--; if (object->ref_count == 0) { pmap_remove_all(m); if (m->dirty == 0) vm_page_cache(m); else vm_page_deactivate(m); } else { vm_page_deactivate(m); } } else { vm_page_requeue(m); } } VM_OBJECT_UNLOCK(object); m = next; } vm_page_unlock_queues(); #if !defined(NO_SWAPPING) /* * Idle process swapout -- run once per second. */ if (vm_swap_idle_enabled) { static long lsec; if (time_second != lsec) { vm_req_vmdaemon(VM_SWAP_IDLE); lsec = time_second; } } #endif /* * If we didn't get enough free pages, and we have skipped a vnode * in a writeable object, wakeup the sync daemon. And kick swapout * if we did not get enough free pages. */ if (vm_paging_target() > 0) { if (vnodes_skipped && vm_page_count_min()) (void) speedup_syncer(); #if !defined(NO_SWAPPING) if (vm_swap_enabled && vm_page_count_target()) vm_req_vmdaemon(VM_SWAP_NORMAL); #endif } /* * If we are critically low on one of RAM or swap and low on * the other, kill the largest process. However, we avoid * doing this on the first pass in order to give ourselves a * chance to flush out dirty vnode-backed pages and to allow * active pages to be moved to the inactive queue and reclaimed. */ if (pass != 0 && ((swap_pager_avail < 64 && vm_page_count_min()) || (swap_pager_full && vm_paging_target() > 0))) vm_pageout_oom(VM_OOM_MEM); } void vm_pageout_oom(int shortage) { struct proc *p, *bigproc; vm_offset_t size, bigsize; struct thread *td; /* * We keep the process bigproc locked once we find it to keep anyone * from messing with it; however, there is a possibility of * deadlock if process B is bigproc and one of it's child processes * attempts to propagate a signal to B while we are waiting for A's * lock while walking this list. To avoid this, we don't block on * the process lock but just skip a process if it is already locked. */ bigproc = NULL; bigsize = 0; sx_slock(&allproc_lock); FOREACH_PROC_IN_SYSTEM(p) { int breakout; if (PROC_TRYLOCK(p) == 0) continue; /* * If this is a system or protected process, skip it. */ if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) || (p->p_flag & P_PROTECTED) || ((p->p_pid < 48) && (swap_pager_avail != 0))) { PROC_UNLOCK(p); continue; } /* * If the process is in a non-running type state, * don't touch it. Check all the threads individually. */ breakout = 0; FOREACH_THREAD_IN_PROC(p, td) { thread_lock(td); if (!TD_ON_RUNQ(td) && !TD_IS_RUNNING(td) && !TD_IS_SLEEPING(td)) { thread_unlock(td); breakout = 1; break; } thread_unlock(td); } if (breakout) { PROC_UNLOCK(p); continue; } /* * get the process size */ if (!vm_map_trylock_read(&p->p_vmspace->vm_map)) { PROC_UNLOCK(p); continue; } size = vmspace_swap_count(p->p_vmspace); vm_map_unlock_read(&p->p_vmspace->vm_map); if (shortage == VM_OOM_MEM) size += vmspace_resident_count(p->p_vmspace); /* * if the this process is bigger than the biggest one * remember it. */ if (size > bigsize) { if (bigproc != NULL) PROC_UNLOCK(bigproc); bigproc = p; bigsize = size; } else PROC_UNLOCK(p); } sx_sunlock(&allproc_lock); if (bigproc != NULL) { killproc(bigproc, "out of swap space"); sched_nice(bigproc, PRIO_MIN); PROC_UNLOCK(bigproc); wakeup(&cnt.v_free_count); } } /* * This routine tries to maintain the pseudo LRU active queue, * so that during long periods of time where there is no paging, * that some statistic accumulation still occurs. This code * helps the situation where paging just starts to occur. */ static void vm_pageout_page_stats() { vm_object_t object; vm_page_t m,next; int pcount,tpcount; /* Number of pages to check */ static int fullintervalcount = 0; int page_shortage; mtx_assert(&vm_page_queue_mtx, MA_OWNED); page_shortage = (cnt.v_inactive_target + cnt.v_cache_max + cnt.v_free_min) - (cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count); if (page_shortage <= 0) return; pcount = cnt.v_active_count; fullintervalcount += vm_pageout_stats_interval; if (fullintervalcount < vm_pageout_full_stats_interval) { tpcount = (int64_t)vm_pageout_stats_max * cnt.v_active_count / cnt.v_page_count; if (pcount > tpcount) pcount = tpcount; } else { fullintervalcount = 0; } m = TAILQ_FIRST(&vm_page_queues[PQ_ACTIVE].pl); while ((m != NULL) && (pcount-- > 0)) { int actcount; KASSERT(VM_PAGE_INQUEUE2(m, PQ_ACTIVE), ("vm_pageout_page_stats: page %p isn't active", m)); next = TAILQ_NEXT(m, pageq); object = m->object; if ((m->flags & PG_MARKER) != 0) { m = next; continue; } if (!VM_OBJECT_TRYLOCK(object) && !vm_pageout_fallback_object_lock(m, &next)) { VM_OBJECT_UNLOCK(object); m = next; continue; } /* * Don't deactivate pages that are busy. */ if ((m->busy != 0) || (m->oflags & VPO_BUSY) || (m->hold_count != 0)) { VM_OBJECT_UNLOCK(object); vm_page_requeue(m); m = next; continue; } actcount = 0; if (m->flags & PG_REFERENCED) { vm_page_flag_clear(m, PG_REFERENCED); actcount += 1; } actcount += pmap_ts_referenced(m); if (actcount) { m->act_count += ACT_ADVANCE + actcount; if (m->act_count > ACT_MAX) m->act_count = ACT_MAX; vm_page_requeue(m); } else { if (m->act_count == 0) { /* * We turn off page access, so that we have * more accurate RSS stats. We don't do this * in the normal page deactivation when the * system is loaded VM wise, because the * cost of the large number of page protect * operations would be higher than the value * of doing the operation. */ pmap_remove_all(m); vm_page_deactivate(m); } else { m->act_count -= min(m->act_count, ACT_DECLINE); vm_page_requeue(m); } } VM_OBJECT_UNLOCK(object); m = next; } } /* * vm_pageout is the high level pageout daemon. */ static void vm_pageout() { int error, pass; /* * Initialize some paging parameters. */ cnt.v_interrupt_free_min = 2; if (cnt.v_page_count < 2000) vm_pageout_page_count = 8; /* * v_free_reserved needs to include enough for the largest * swap pager structures plus enough for any pv_entry structs * when paging. */ if (cnt.v_page_count > 1024) cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200; else cnt.v_free_min = 4; cnt.v_pageout_free_min = (2*MAXBSIZE)/PAGE_SIZE + cnt.v_interrupt_free_min; cnt.v_free_reserved = vm_pageout_page_count + cnt.v_pageout_free_min + (cnt.v_page_count / 768); cnt.v_free_severe = cnt.v_free_min / 2; cnt.v_free_min += cnt.v_free_reserved; cnt.v_free_severe += cnt.v_free_reserved; /* * v_free_target and v_cache_min control pageout hysteresis. Note * that these are more a measure of the VM cache queue hysteresis * then the VM free queue. Specifically, v_free_target is the * high water mark (free+cache pages). * * v_free_reserved + v_cache_min (mostly means v_cache_min) is the * low water mark, while v_free_min is the stop. v_cache_min must * be big enough to handle memory needs while the pageout daemon * is signalled and run to free more pages. */ if (cnt.v_free_count > 6144) cnt.v_free_target = 4 * cnt.v_free_min + cnt.v_free_reserved; else cnt.v_free_target = 2 * cnt.v_free_min + cnt.v_free_reserved; if (cnt.v_free_count > 2048) { cnt.v_cache_min = cnt.v_free_target; cnt.v_cache_max = 2 * cnt.v_cache_min; cnt.v_inactive_target = (3 * cnt.v_free_target) / 2; } else { cnt.v_cache_min = 0; cnt.v_cache_max = 0; cnt.v_inactive_target = cnt.v_free_count / 4; } if (cnt.v_inactive_target > cnt.v_free_count / 3) cnt.v_inactive_target = cnt.v_free_count / 3; /* XXX does not really belong here */ if (vm_page_max_wired == 0) vm_page_max_wired = cnt.v_free_count / 3; if (vm_pageout_stats_max == 0) vm_pageout_stats_max = cnt.v_free_target; /* * Set interval in seconds for stats scan. */ if (vm_pageout_stats_interval == 0) vm_pageout_stats_interval = 5; if (vm_pageout_full_stats_interval == 0) vm_pageout_full_stats_interval = vm_pageout_stats_interval * 4; swap_pager_swap_init(); pass = 0; /* * The pageout daemon is never done, so loop forever. */ while (TRUE) { /* * If we have enough free memory, wakeup waiters. Do * not clear vm_pages_needed until we reach our target, * otherwise we may be woken up over and over again and * waste a lot of cpu. */ mtx_lock(&vm_page_queue_free_mtx); if (vm_pages_needed && !vm_page_count_min()) { if (!vm_paging_needed()) vm_pages_needed = 0; wakeup(&cnt.v_free_count); } if (vm_pages_needed) { /* * Still not done, take a second pass without waiting * (unlimited dirty cleaning), otherwise sleep a bit * and try again. */ ++pass; if (pass > 1) msleep(&vm_pages_needed, &vm_page_queue_free_mtx, PVM, "psleep", hz / 2); } else { /* * Good enough, sleep & handle stats. Prime the pass * for the next run. */ if (pass > 1) pass = 1; else pass = 0; error = msleep(&vm_pages_needed, &vm_page_queue_free_mtx, PVM, "psleep", vm_pageout_stats_interval * hz); if (error && !vm_pages_needed) { mtx_unlock(&vm_page_queue_free_mtx); pass = 0; vm_page_lock_queues(); vm_pageout_page_stats(); vm_page_unlock_queues(); continue; } } if (vm_pages_needed) cnt.v_pdwakeups++; mtx_unlock(&vm_page_queue_free_mtx); vm_pageout_scan(pass); } } /* * Unless the free page queue lock is held by the caller, this function * should be regarded as advisory. Specifically, the caller should * not msleep() on &cnt.v_free_count following this function unless * the free page queue lock is held until the msleep() is performed. */ void pagedaemon_wakeup() { if (!vm_pages_needed && curthread->td_proc != pageproc) { vm_pages_needed = 1; wakeup(&vm_pages_needed); } } #if !defined(NO_SWAPPING) static void vm_req_vmdaemon(int req) { static int lastrun = 0; mtx_lock(&vm_daemon_mtx); vm_pageout_req_swapout |= req; if ((ticks > (lastrun + hz)) || (ticks < lastrun)) { wakeup(&vm_daemon_needed); lastrun = ticks; } mtx_unlock(&vm_daemon_mtx); } static void vm_daemon() { struct rlimit rsslim; struct proc *p; struct thread *td; int breakout, swapout_flags; while (TRUE) { mtx_lock(&vm_daemon_mtx); msleep(&vm_daemon_needed, &vm_daemon_mtx, PPAUSE, "psleep", 0); swapout_flags = vm_pageout_req_swapout; vm_pageout_req_swapout = 0; mtx_unlock(&vm_daemon_mtx); if (swapout_flags) swapout_procs(swapout_flags); /* * scan the processes for exceeding their rlimits or if * process is swapped out -- deactivate pages */ sx_slock(&allproc_lock); FOREACH_PROC_IN_SYSTEM(p) { vm_pindex_t limit, size; /* * if this is a system process or if we have already * looked at this process, skip it. */ PROC_LOCK(p); if (p->p_flag & (P_SYSTEM | P_WEXIT)) { PROC_UNLOCK(p); continue; } /* * if the process is in a non-running type state, * don't touch it. */ breakout = 0; FOREACH_THREAD_IN_PROC(p, td) { thread_lock(td); if (!TD_ON_RUNQ(td) && !TD_IS_RUNNING(td) && !TD_IS_SLEEPING(td)) { thread_unlock(td); breakout = 1; break; } thread_unlock(td); } if (breakout) { PROC_UNLOCK(p); continue; } /* * get a limit */ lim_rlimit(p, RLIMIT_RSS, &rsslim); limit = OFF_TO_IDX( qmin(rsslim.rlim_cur, rsslim.rlim_max)); /* * let processes that are swapped out really be * swapped out set the limit to nothing (will force a * swap-out.) */ if ((p->p_flag & P_INMEM) == 0) limit = 0; /* XXX */ PROC_UNLOCK(p); size = vmspace_resident_count(p->p_vmspace); if (limit >= 0 && size >= limit) { vm_pageout_map_deactivate_pages( &p->p_vmspace->vm_map, limit); } } sx_sunlock(&allproc_lock); } } #endif /* !defined(NO_SWAPPING) */