/* $NetBSD: uvm_pdaemon.c,v 1.96 2008/12/03 11:43:51 ad Exp $ */ /* * Copyright (c) 1997 Charles D. Cranor and Washington University. * Copyright (c) 1991, 1993, The Regents of the University of California. * * 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 Charles D. Cranor, * Washington University, 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. * * @(#)vm_pageout.c 8.5 (Berkeley) 2/14/94 * from: Id: uvm_pdaemon.c,v 1.1.2.32 1998/02/06 05:26:30 chs Exp * * * Copyright (c) 1987, 1990 Carnegie-Mellon University. * All rights reserved. * * 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. */ /* * uvm_pdaemon.c: the page daemon */ #include __KERNEL_RCSID(0, "$NetBSD: uvm_pdaemon.c,v 1.96 2008/12/03 11:43:51 ad Exp $"); #include "opt_uvmhist.h" #include "opt_readahead.h" #include #include #include #include #include #include #include #include #include #include /* * UVMPD_NUMDIRTYREACTS is how many dirty pages the pagedaemon will reactivate * in a pass thru the inactive list when swap is full. the value should be * "small"... if it's too large we'll cycle the active pages thru the inactive * queue too quickly to for them to be referenced and avoid being freed. */ #define UVMPD_NUMDIRTYREACTS 16 #define UVMPD_NUMTRYLOCKOWNER 16 /* * local prototypes */ static void uvmpd_scan(void); static void uvmpd_scan_queue(void); static void uvmpd_tune(void); unsigned int uvm_pagedaemon_waiters; /* * XXX hack to avoid hangs when large processes fork. */ u_int uvm_extrapages; /* * uvm_wait: wait (sleep) for the page daemon to free some pages * * => should be called with all locks released * => should _not_ be called by the page daemon (to avoid deadlock) */ void uvm_wait(const char *wmsg) { int timo = 0; mutex_spin_enter(&uvm_fpageqlock); /* * check for page daemon going to sleep (waiting for itself) */ if (curlwp == uvm.pagedaemon_lwp && uvmexp.paging == 0) { /* * now we have a problem: the pagedaemon wants to go to * sleep until it frees more memory. but how can it * free more memory if it is asleep? that is a deadlock. * we have two options: * [1] panic now * [2] put a timeout on the sleep, thus causing the * pagedaemon to only pause (rather than sleep forever) * * note that option [2] will only help us if we get lucky * and some other process on the system breaks the deadlock * by exiting or freeing memory (thus allowing the pagedaemon * to continue). for now we panic if DEBUG is defined, * otherwise we hope for the best with option [2] (better * yet, this should never happen in the first place!). */ printf("pagedaemon: deadlock detected!\n"); timo = hz >> 3; /* set timeout */ #if defined(DEBUG) /* DEBUG: panic so we can debug it */ panic("pagedaemon deadlock"); #endif } uvm_pagedaemon_waiters++; wakeup(&uvm.pagedaemon); /* wake the daemon! */ UVM_UNLOCK_AND_WAIT(&uvmexp.free, &uvm_fpageqlock, false, wmsg, timo); } /* * uvm_kick_pdaemon: perform checks to determine if we need to * give the pagedaemon a nudge, and do so if necessary. * * => called with uvm_fpageqlock held. */ void uvm_kick_pdaemon(void) { KASSERT(mutex_owned(&uvm_fpageqlock)); if (uvmexp.free + uvmexp.paging < uvmexp.freemin || (uvmexp.free + uvmexp.paging < uvmexp.freetarg && uvmpdpol_needsscan_p())) { wakeup(&uvm.pagedaemon); } } /* * uvmpd_tune: tune paging parameters * * => called when ever memory is added (or removed?) to the system * => caller must call with page queues locked */ static void uvmpd_tune(void) { int val; UVMHIST_FUNC("uvmpd_tune"); UVMHIST_CALLED(pdhist); /* * try to keep 0.5% of available RAM free, but limit to between * 128k and 1024k per-CPU. XXX: what are these values good for? */ val = uvmexp.npages / 200; val = MAX(val, (128*1024) >> PAGE_SHIFT); val = MIN(val, (1024*1024) >> PAGE_SHIFT); val *= ncpu; /* Make sure there's always a user page free. */ if (val < uvmexp.reserve_kernel + 1) val = uvmexp.reserve_kernel + 1; uvmexp.freemin = val; /* Calculate free target. */ val = (uvmexp.freemin * 4) / 3; if (val <= uvmexp.freemin) val = uvmexp.freemin + 1; uvmexp.freetarg = val + atomic_swap_uint(&uvm_extrapages, 0); uvmexp.wiredmax = uvmexp.npages / 3; UVMHIST_LOG(pdhist, "<- done, freemin=%d, freetarg=%d, wiredmax=%d", uvmexp.freemin, uvmexp.freetarg, uvmexp.wiredmax, 0); } /* * uvm_pageout: the main loop for the pagedaemon */ void uvm_pageout(void *arg) { int bufcnt, npages = 0; int extrapages = 0; struct pool *pp; uint64_t where; UVMHIST_FUNC("uvm_pageout"); UVMHIST_CALLED(pdhist); UVMHIST_LOG(pdhist,"", 0, 0, 0, 0); /* * ensure correct priority and set paging parameters... */ uvm.pagedaemon_lwp = curlwp; mutex_enter(&uvm_pageqlock); npages = uvmexp.npages; uvmpd_tune(); mutex_exit(&uvm_pageqlock); /* * main loop */ for (;;) { bool needsscan, needsfree; mutex_spin_enter(&uvm_fpageqlock); if (uvm_pagedaemon_waiters == 0 || uvmexp.paging > 0) { UVMHIST_LOG(pdhist," <>",0,0,0,0); UVM_UNLOCK_AND_WAIT(&uvm.pagedaemon, &uvm_fpageqlock, false, "pgdaemon", 0); uvmexp.pdwoke++; UVMHIST_LOG(pdhist," <>",0,0,0,0); } else { mutex_spin_exit(&uvm_fpageqlock); } /* * now lock page queues and recompute inactive count */ mutex_enter(&uvm_pageqlock); if (npages != uvmexp.npages || extrapages != uvm_extrapages) { npages = uvmexp.npages; extrapages = uvm_extrapages; mutex_spin_enter(&uvm_fpageqlock); uvmpd_tune(); mutex_spin_exit(&uvm_fpageqlock); } uvmpdpol_tune(); /* * Estimate a hint. Note that bufmem are returned to * system only when entire pool page is empty. */ mutex_spin_enter(&uvm_fpageqlock); bufcnt = uvmexp.freetarg - uvmexp.free; if (bufcnt < 0) bufcnt = 0; UVMHIST_LOG(pdhist," free/ftarg=%d/%d", uvmexp.free, uvmexp.freetarg, 0,0); needsfree = uvmexp.free + uvmexp.paging < uvmexp.freetarg; needsscan = needsfree || uvmpdpol_needsscan_p(); mutex_spin_exit(&uvm_fpageqlock); /* * scan if needed */ if (needsscan) uvmpd_scan(); /* * if there's any free memory to be had, * wake up any waiters. */ mutex_spin_enter(&uvm_fpageqlock); if (uvmexp.free > uvmexp.reserve_kernel || uvmexp.paging == 0) { wakeup(&uvmexp.free); uvm_pagedaemon_waiters = 0; } mutex_spin_exit(&uvm_fpageqlock); /* * scan done. unlock page queues (the only lock we are holding) */ mutex_exit(&uvm_pageqlock); /* * if we don't need free memory, we're done. */ if (!needsfree) continue; /* * start draining pool resources now that we're not * holding any locks. */ pool_drain_start(&pp, &where); /* * kill unused metadata buffers. */ mutex_enter(&bufcache_lock); buf_drain(bufcnt << PAGE_SHIFT); mutex_exit(&bufcache_lock); /* * complete draining the pools. */ pool_drain_end(pp, where); } /*NOTREACHED*/ } /* * uvm_aiodone_worker: a workqueue callback for the aiodone daemon. */ void uvm_aiodone_worker(struct work *wk, void *dummy) { struct buf *bp = (void *)wk; KASSERT(&bp->b_work == wk); /* * process an i/o that's done. */ (*bp->b_iodone)(bp); } void uvm_pageout_start(int npages) { mutex_spin_enter(&uvm_fpageqlock); uvmexp.paging += npages; mutex_spin_exit(&uvm_fpageqlock); } void uvm_pageout_done(int npages) { mutex_spin_enter(&uvm_fpageqlock); KASSERT(uvmexp.paging >= npages); uvmexp.paging -= npages; /* * wake up either of pagedaemon or LWPs waiting for it. */ if (uvmexp.free <= uvmexp.reserve_kernel) { wakeup(&uvm.pagedaemon); } else { wakeup(&uvmexp.free); uvm_pagedaemon_waiters = 0; } mutex_spin_exit(&uvm_fpageqlock); } /* * uvmpd_trylockowner: trylock the page's owner. * * => called with pageq locked. * => resolve orphaned O->A loaned page. * => return the locked mutex on success. otherwise, return NULL. */ kmutex_t * uvmpd_trylockowner(struct vm_page *pg) { struct uvm_object *uobj = pg->uobject; kmutex_t *slock; KASSERT(mutex_owned(&uvm_pageqlock)); if (uobj != NULL) { slock = &uobj->vmobjlock; } else { struct vm_anon *anon = pg->uanon; KASSERT(anon != NULL); slock = &anon->an_lock; } if (!mutex_tryenter(slock)) { return NULL; } if (uobj == NULL) { /* * set PQ_ANON if it isn't set already. */ if ((pg->pqflags & PQ_ANON) == 0) { KASSERT(pg->loan_count > 0); pg->loan_count--; pg->pqflags |= PQ_ANON; /* anon now owns it */ } } return slock; } #if defined(VMSWAP) struct swapcluster { int swc_slot; int swc_nallocated; int swc_nused; struct vm_page *swc_pages[howmany(MAXPHYS, MIN_PAGE_SIZE)]; }; static void swapcluster_init(struct swapcluster *swc) { swc->swc_slot = 0; swc->swc_nused = 0; } static int swapcluster_allocslots(struct swapcluster *swc) { int slot; int npages; if (swc->swc_slot != 0) { return 0; } /* Even with strange MAXPHYS, the shift implicitly rounds down to a page. */ npages = MAXPHYS >> PAGE_SHIFT; slot = uvm_swap_alloc(&npages, true); if (slot == 0) { return ENOMEM; } swc->swc_slot = slot; swc->swc_nallocated = npages; swc->swc_nused = 0; return 0; } static int swapcluster_add(struct swapcluster *swc, struct vm_page *pg) { int slot; struct uvm_object *uobj; KASSERT(swc->swc_slot != 0); KASSERT(swc->swc_nused < swc->swc_nallocated); KASSERT((pg->pqflags & PQ_SWAPBACKED) != 0); slot = swc->swc_slot + swc->swc_nused; uobj = pg->uobject; if (uobj == NULL) { KASSERT(mutex_owned(&pg->uanon->an_lock)); pg->uanon->an_swslot = slot; } else { int result; KASSERT(mutex_owned(&uobj->vmobjlock)); result = uao_set_swslot(uobj, pg->offset >> PAGE_SHIFT, slot); if (result == -1) { return ENOMEM; } } swc->swc_pages[swc->swc_nused] = pg; swc->swc_nused++; return 0; } static void swapcluster_flush(struct swapcluster *swc, bool now) { int slot; int nused; int nallocated; int error; if (swc->swc_slot == 0) { return; } KASSERT(swc->swc_nused <= swc->swc_nallocated); slot = swc->swc_slot; nused = swc->swc_nused; nallocated = swc->swc_nallocated; /* * if this is the final pageout we could have a few * unused swap blocks. if so, free them now. */ if (nused < nallocated) { if (!now) { return; } uvm_swap_free(slot + nused, nallocated - nused); } /* * now start the pageout. */ if (nused > 0) { uvmexp.pdpageouts++; uvm_pageout_start(nused); error = uvm_swap_put(slot, swc->swc_pages, nused, 0); KASSERT(error == 0 || error == ENOMEM); } /* * zero swslot to indicate that we are * no longer building a swap-backed cluster. */ swc->swc_slot = 0; swc->swc_nused = 0; } static int swapcluster_nused(struct swapcluster *swc) { return swc->swc_nused; } /* * uvmpd_dropswap: free any swap allocated to this page. * * => called with owner locked. * => return true if a page had an associated slot. */ static bool uvmpd_dropswap(struct vm_page *pg) { bool result = false; struct vm_anon *anon = pg->uanon; if ((pg->pqflags & PQ_ANON) && anon->an_swslot) { uvm_swap_free(anon->an_swslot, 1); anon->an_swslot = 0; pg->flags &= ~PG_CLEAN; result = true; } else if (pg->pqflags & PQ_AOBJ) { int slot = uao_set_swslot(pg->uobject, pg->offset >> PAGE_SHIFT, 0); if (slot) { uvm_swap_free(slot, 1); pg->flags &= ~PG_CLEAN; result = true; } } return result; } /* * uvmpd_trydropswap: try to free any swap allocated to this page. * * => return true if a slot is successfully freed. */ bool uvmpd_trydropswap(struct vm_page *pg) { kmutex_t *slock; bool result; if ((pg->flags & PG_BUSY) != 0) { return false; } /* * lock the page's owner. */ slock = uvmpd_trylockowner(pg); if (slock == NULL) { return false; } /* * skip this page if it's busy. */ if ((pg->flags & PG_BUSY) != 0) { mutex_exit(slock); return false; } result = uvmpd_dropswap(pg); mutex_exit(slock); return result; } #endif /* defined(VMSWAP) */ /* * uvmpd_scan_queue: scan an replace candidate list for pages * to clean or free. * * => called with page queues locked * => we work on meeting our free target by converting inactive pages * into free pages. * => we handle the building of swap-backed clusters */ static void uvmpd_scan_queue(void) { struct vm_page *p; struct uvm_object *uobj; struct vm_anon *anon; #if defined(VMSWAP) struct swapcluster swc; #endif /* defined(VMSWAP) */ int dirtyreacts; int lockownerfail; kmutex_t *slock; UVMHIST_FUNC("uvmpd_scan_queue"); UVMHIST_CALLED(pdhist); /* * swslot is non-zero if we are building a swap cluster. we want * to stay in the loop while we have a page to scan or we have * a swap-cluster to build. */ #if defined(VMSWAP) swapcluster_init(&swc); #endif /* defined(VMSWAP) */ dirtyreacts = 0; lockownerfail = 0; uvmpdpol_scaninit(); while (/* CONSTCOND */ 1) { /* * see if we've met the free target. */ if (uvmexp.free + uvmexp.paging #if defined(VMSWAP) + swapcluster_nused(&swc) #endif /* defined(VMSWAP) */ >= uvmexp.freetarg << 2 || dirtyreacts == UVMPD_NUMDIRTYREACTS) { UVMHIST_LOG(pdhist," met free target: " "exit loop", 0, 0, 0, 0); break; } p = uvmpdpol_selectvictim(); if (p == NULL) { break; } KASSERT(uvmpdpol_pageisqueued_p(p)); KASSERT(p->wire_count == 0); /* * we are below target and have a new page to consider. */ anon = p->uanon; uobj = p->uobject; /* * first we attempt to lock the object that this page * belongs to. if our attempt fails we skip on to * the next page (no harm done). it is important to * "try" locking the object as we are locking in the * wrong order (pageq -> object) and we don't want to * deadlock. * * the only time we expect to see an ownerless page * (i.e. a page with no uobject and !PQ_ANON) is if an * anon has loaned a page from a uvm_object and the * uvm_object has dropped the ownership. in that * case, the anon can "take over" the loaned page * and make it its own. */ slock = uvmpd_trylockowner(p); if (slock == NULL) { /* * yield cpu to make a chance for an LWP holding * the lock run. otherwise we can busy-loop too long * if the page queue is filled with a lot of pages * from few objects. */ lockownerfail++; if (lockownerfail > UVMPD_NUMTRYLOCKOWNER) { mutex_exit(&uvm_pageqlock); /* XXX Better than yielding but inadequate. */ kpause("livelock", false, 1, NULL); mutex_enter(&uvm_pageqlock); lockownerfail = 0; } continue; } if (p->flags & PG_BUSY) { mutex_exit(slock); uvmexp.pdbusy++; continue; } /* does the page belong to an object? */ if (uobj != NULL) { uvmexp.pdobscan++; } else { #if defined(VMSWAP) KASSERT(anon != NULL); uvmexp.pdanscan++; #else /* defined(VMSWAP) */ panic("%s: anon", __func__); #endif /* defined(VMSWAP) */ } /* * we now have the object and the page queues locked. * if the page is not swap-backed, call the object's * pager to flush and free the page. */ #if defined(READAHEAD_STATS) if ((p->pqflags & PQ_READAHEAD) != 0) { p->pqflags &= ~PQ_READAHEAD; uvm_ra_miss.ev_count++; } #endif /* defined(READAHEAD_STATS) */ if ((p->pqflags & PQ_SWAPBACKED) == 0) { KASSERT(uobj != NULL); mutex_exit(&uvm_pageqlock); (void) (uobj->pgops->pgo_put)(uobj, p->offset, p->offset + PAGE_SIZE, PGO_CLEANIT|PGO_FREE); mutex_enter(&uvm_pageqlock); continue; } /* * the page is swap-backed. remove all the permissions * from the page so we can sync the modified info * without any race conditions. if the page is clean * we can free it now and continue. */ pmap_page_protect(p, VM_PROT_NONE); if ((p->flags & PG_CLEAN) && pmap_clear_modify(p)) { p->flags &= ~(PG_CLEAN); } if (p->flags & PG_CLEAN) { int slot; int pageidx; pageidx = p->offset >> PAGE_SHIFT; uvm_pagefree(p); uvmexp.pdfreed++; /* * for anons, we need to remove the page * from the anon ourselves. for aobjs, * pagefree did that for us. */ if (anon) { KASSERT(anon->an_swslot != 0); anon->an_page = NULL; slot = anon->an_swslot; } else { slot = uao_find_swslot(uobj, pageidx); } mutex_exit(slock); if (slot > 0) { /* this page is now only in swap. */ mutex_enter(&uvm_swap_data_lock); KASSERT(uvmexp.swpgonly < uvmexp.swpginuse); uvmexp.swpgonly++; mutex_exit(&uvm_swap_data_lock); } continue; } #if defined(VMSWAP) /* * this page is dirty, skip it if we'll have met our * free target when all the current pageouts complete. */ if (uvmexp.free + uvmexp.paging > uvmexp.freetarg << 2) { mutex_exit(slock); continue; } /* * free any swap space allocated to the page since * we'll have to write it again with its new data. */ uvmpd_dropswap(p); /* * if all pages in swap are only in swap, * the swap space is full and we can't page out * any more swap-backed pages. reactivate this page * so that we eventually cycle all pages through * the inactive queue. */ if (uvm_swapisfull()) { dirtyreacts++; uvm_pageactivate(p); mutex_exit(slock); continue; } /* * start new swap pageout cluster (if necessary). */ if (swapcluster_allocslots(&swc)) { mutex_exit(slock); dirtyreacts++; /* XXX */ continue; } /* * at this point, we're definitely going reuse this * page. mark the page busy and delayed-free. * we should remove the page from the page queues * so we don't ever look at it again. * adjust counters and such. */ p->flags |= PG_BUSY; UVM_PAGE_OWN(p, "scan_queue"); p->flags |= PG_PAGEOUT; uvm_pagedequeue(p); uvmexp.pgswapout++; mutex_exit(&uvm_pageqlock); /* * add the new page to the cluster. */ if (swapcluster_add(&swc, p)) { p->flags &= ~(PG_BUSY|PG_PAGEOUT); UVM_PAGE_OWN(p, NULL); mutex_enter(&uvm_pageqlock); dirtyreacts++; uvm_pageactivate(p); mutex_exit(slock); continue; } mutex_exit(slock); swapcluster_flush(&swc, false); mutex_enter(&uvm_pageqlock); /* * the pageout is in progress. bump counters and set up * for the next loop. */ uvmexp.pdpending++; #else /* defined(VMSWAP) */ uvm_pageactivate(p); mutex_exit(slock); #endif /* defined(VMSWAP) */ } #if defined(VMSWAP) mutex_exit(&uvm_pageqlock); swapcluster_flush(&swc, true); mutex_enter(&uvm_pageqlock); #endif /* defined(VMSWAP) */ } /* * uvmpd_scan: scan the page queues and attempt to meet our targets. * * => called with pageq's locked */ static void uvmpd_scan(void) { int swap_shortage, pages_freed; UVMHIST_FUNC("uvmpd_scan"); UVMHIST_CALLED(pdhist); uvmexp.pdrevs++; /* * work on meeting our targets. first we work on our free target * by converting inactive pages into free pages. then we work on * meeting our inactive target by converting active pages to * inactive ones. */ UVMHIST_LOG(pdhist, " starting 'free' loop",0,0,0,0); pages_freed = uvmexp.pdfreed; uvmpd_scan_queue(); pages_freed = uvmexp.pdfreed - pages_freed; /* * detect if we're not going to be able to page anything out * until we free some swap resources from active pages. */ swap_shortage = 0; if (uvmexp.free < uvmexp.freetarg && uvmexp.swpginuse >= uvmexp.swpgavail && !uvm_swapisfull() && pages_freed == 0) { swap_shortage = uvmexp.freetarg - uvmexp.free; } uvmpdpol_balancequeue(swap_shortage); /* * swap out some processes if we are still below the minimum * free target. we need to unlock the page queues for this. */ if (uvmexp.free < uvmexp.freemin && uvmexp.nswapdev != 0 && uvm.swapout_enabled) { uvmexp.pdswout++; UVMHIST_LOG(pdhist," free %d < min %d: swapout", uvmexp.free, uvmexp.freemin, 0, 0); mutex_exit(&uvm_pageqlock); uvm_swapout_threads(); mutex_enter(&uvm_pageqlock); } /* * if still below the minimum target, try unloading kernel * modules. */ if (uvmexp.free < uvmexp.freemin) { module_thread_kick(); } } /* * uvm_reclaimable: decide whether to wait for pagedaemon. * * => return true if it seems to be worth to do uvm_wait. * * XXX should be tunable. * XXX should consider pools, etc? */ bool uvm_reclaimable(void) { int filepages; int active, inactive; /* * if swap is not full, no problem. */ if (!uvm_swapisfull()) { return true; } /* * file-backed pages can be reclaimed even when swap is full. * if we have more than 1/16 of pageable memory or 5MB, try to reclaim. * * XXX assume the worst case, ie. all wired pages are file-backed. * * XXX should consider about other reclaimable memory. * XXX ie. pools, traditional buffer cache. */ filepages = uvmexp.filepages + uvmexp.execpages - uvmexp.wired; uvm_estimatepageable(&active, &inactive); if (filepages >= MIN((active + inactive) >> 4, 5 * 1024 * 1024 >> PAGE_SHIFT)) { return true; } /* * kill the process, fail allocation, etc.. */ return false; } void uvm_estimatepageable(int *active, int *inactive) { uvmpdpol_estimatepageable(active, inactive); }