/* * Copyright (c) 1991 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 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_page.c 7.4 (Berkeley) 5/7/91 * $FreeBSD$ */ /* * 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. */ /* * GENERAL RULES ON VM_PAGE MANIPULATION * * - a pageq mutex is required when adding or removing a page from a * page queue (vm_page_queue[]), regardless of other mutexes or the * busy state of a page. * * - a hash chain mutex is required when associating or disassociating * a page from the VM PAGE CACHE hash table (vm_page_buckets), * regardless of other mutexes or the busy state of a page. * * - either a hash chain mutex OR a busied page is required in order * to modify the page flags. A hash chain mutex must be obtained in * order to busy a page. A page's flags cannot be modified by a * hash chain mutex if the page is marked busy. * * - The object memq mutex is held when inserting or removing * pages from an object (vm_page_insert() or vm_page_remove()). This * is different from the object's main mutex. * * Generally speaking, you have to be aware of side effects when running * vm_page ops. A vm_page_lookup() will return with the hash chain * locked, whether it was able to lookup the page or not. vm_page_free(), * vm_page_cache(), vm_page_activate(), and a number of other routines * will release the hash chain mutex for you. Intermediate manipulation * routines such as vm_page_flag_set() expect the hash chain to be held * on entry and the hash chain will remain held on return. * * pageq scanning can only occur with the pageq in question locked. * We have a known bottleneck with the active queue, but the cache * and free queues are actually arrays already. */ /* * Resident memory management module. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Associated with page of user-allocatable memory is a * page structure. */ static struct mtx vm_page_buckets_mtx; static struct vm_page **vm_page_buckets; /* Array of buckets */ static int vm_page_bucket_count; /* How big is array? */ static int vm_page_hash_mask; /* Mask for hash function */ struct mtx vm_page_queue_mtx; struct mtx vm_page_queue_free_mtx; vm_page_t vm_page_array = 0; int vm_page_array_size = 0; long first_page = 0; int vm_page_zero_count = 0; /* * vm_set_page_size: * * Sets the page size, perhaps based upon the memory * size. Must be called before any use of page-size * dependent functions. */ void vm_set_page_size(void) { if (cnt.v_page_size == 0) cnt.v_page_size = PAGE_SIZE; if (((cnt.v_page_size - 1) & cnt.v_page_size) != 0) panic("vm_set_page_size: page size not a power of two"); } /* * vm_page_startup: * * Initializes the resident memory module. * * Allocates memory for the page cells, and * for the object/offset-to-page hash table headers. * Each page cell is initialized and placed on the free list. */ vm_offset_t vm_page_startup(vm_offset_t starta, vm_offset_t enda, vm_offset_t vaddr) { vm_offset_t mapped; struct vm_page **bucket; vm_size_t npages, page_range; vm_offset_t new_end; int i; vm_offset_t pa; int nblocks; vm_offset_t last_pa; /* the biggest memory array is the second group of pages */ vm_offset_t end; vm_offset_t biggestone, biggestsize; vm_offset_t total; vm_size_t bootpages; total = 0; biggestsize = 0; biggestone = 0; nblocks = 0; vaddr = round_page(vaddr); for (i = 0; phys_avail[i + 1]; i += 2) { phys_avail[i] = round_page(phys_avail[i]); phys_avail[i + 1] = trunc_page(phys_avail[i + 1]); } for (i = 0; phys_avail[i + 1]; i += 2) { vm_size_t size = phys_avail[i + 1] - phys_avail[i]; if (size > biggestsize) { biggestone = i; biggestsize = size; } ++nblocks; total += size; } end = phys_avail[biggestone+1]; /* * Initialize the locks. */ mtx_init(&vm_page_queue_mtx, "vm page queue mutex", NULL, MTX_DEF); mtx_init(&vm_page_queue_free_mtx, "vm page queue free mutex", NULL, MTX_SPIN); /* * Initialize the queue headers for the free queue, the active queue * and the inactive queue. */ vm_pageq_init(); /* * Allocate memory for use when boot strapping the kernel memory allocator */ bootpages = UMA_BOOT_PAGES * UMA_SLAB_SIZE; new_end = end - bootpages; new_end = trunc_page(new_end); mapped = pmap_map(&vaddr, new_end, end, VM_PROT_READ | VM_PROT_WRITE); bzero((caddr_t) mapped, end - new_end); uma_startup((caddr_t)mapped); end = new_end; /* * Allocate (and initialize) the hash table buckets. * * The number of buckets MUST BE a power of 2, and the actual value is * the next power of 2 greater than the number of physical pages in * the system. * * We make the hash table approximately 2x the number of pages to * reduce the chain length. This is about the same size using the * singly-linked list as the 1x hash table we were using before * using TAILQ but the chain length will be smaller. * * Note: This computation can be tweaked if desired. */ if (vm_page_bucket_count == 0) { vm_page_bucket_count = 1; while (vm_page_bucket_count < atop(total)) vm_page_bucket_count <<= 1; } vm_page_bucket_count <<= 1; vm_page_hash_mask = vm_page_bucket_count - 1; /* * Validate these addresses. */ new_end = end - vm_page_bucket_count * sizeof(struct vm_page *); new_end = trunc_page(new_end); mapped = pmap_map(&vaddr, new_end, end, VM_PROT_READ | VM_PROT_WRITE); bzero((caddr_t) mapped, end - new_end); mtx_init(&vm_page_buckets_mtx, "vm page buckets mutex", NULL, MTX_SPIN); vm_page_buckets = (struct vm_page **)mapped; bucket = vm_page_buckets; for (i = 0; i < vm_page_bucket_count; i++) { *bucket = NULL; bucket++; } /* * Compute the number of pages of memory that will be available for * use (taking into account the overhead of a page structure per * page). */ first_page = phys_avail[0] / PAGE_SIZE; page_range = phys_avail[(nblocks - 1) * 2 + 1] / PAGE_SIZE - first_page; npages = (total - (page_range * sizeof(struct vm_page)) - (end - new_end)) / PAGE_SIZE; end = new_end; /* * Initialize the mem entry structures now, and put them in the free * queue. */ new_end = trunc_page(end - page_range * sizeof(struct vm_page)); mapped = pmap_map(&vaddr, new_end, end, VM_PROT_READ | VM_PROT_WRITE); vm_page_array = (vm_page_t) mapped; /* * Clear all of the page structures */ bzero((caddr_t) vm_page_array, page_range * sizeof(struct vm_page)); vm_page_array_size = page_range; /* * Construct the free queue(s) in descending order (by physical * address) so that the first 16MB of physical memory is allocated * last rather than first. On large-memory machines, this avoids * the exhaustion of low physical memory before isa_dmainit has run. */ cnt.v_page_count = 0; cnt.v_free_count = 0; for (i = 0; phys_avail[i + 1] && npages > 0; i += 2) { pa = phys_avail[i]; if (i == biggestone) last_pa = new_end; else last_pa = phys_avail[i + 1]; while (pa < last_pa && npages-- > 0) { vm_pageq_add_new_page(pa); pa += PAGE_SIZE; } } return (vaddr); } /* * vm_page_hash: * * Distributes the object/offset key pair among hash buckets. * * NOTE: This macro depends on vm_page_bucket_count being a power of 2. * This routine may not block. * * We try to randomize the hash based on the object to spread the pages * out in the hash table without it costing us too much. */ static __inline int vm_page_hash(vm_object_t object, vm_pindex_t pindex) { int i = ((uintptr_t)object + pindex) ^ object->hash_rand; return (i & vm_page_hash_mask); } void vm_page_flag_set(vm_page_t m, unsigned short bits) { GIANT_REQUIRED; m->flags |= bits; } void vm_page_flag_clear(vm_page_t m, unsigned short bits) { GIANT_REQUIRED; m->flags &= ~bits; } void vm_page_busy(vm_page_t m) { KASSERT((m->flags & PG_BUSY) == 0, ("vm_page_busy: page already busy!!!")); vm_page_flag_set(m, PG_BUSY); } /* * vm_page_flash: * * wakeup anyone waiting for the page. */ void vm_page_flash(vm_page_t m) { if (m->flags & PG_WANTED) { vm_page_flag_clear(m, PG_WANTED); wakeup(m); } } /* * vm_page_wakeup: * * clear the PG_BUSY flag and wakeup anyone waiting for the * page. * */ void vm_page_wakeup(vm_page_t m) { KASSERT(m->flags & PG_BUSY, ("vm_page_wakeup: page not busy!!!")); vm_page_flag_clear(m, PG_BUSY); vm_page_flash(m); } /* * * */ void vm_page_io_start(vm_page_t m) { GIANT_REQUIRED; m->busy++; } void vm_page_io_finish(vm_page_t m) { GIANT_REQUIRED; m->busy--; if (m->busy == 0) vm_page_flash(m); } /* * Keep page from being freed by the page daemon * much of the same effect as wiring, except much lower * overhead and should be used only for *very* temporary * holding ("wiring"). */ void vm_page_hold(vm_page_t mem) { GIANT_REQUIRED; mem->hold_count++; } void vm_page_unhold(vm_page_t mem) { GIANT_REQUIRED; --mem->hold_count; KASSERT(mem->hold_count >= 0, ("vm_page_unhold: hold count < 0!!!")); if (mem->hold_count == 0 && mem->queue == PQ_HOLD) vm_page_free_toq(mem); } /* * vm_page_protect: * * Reduce the protection of a page. This routine never raises the * protection and therefore can be safely called if the page is already * at VM_PROT_NONE (it will be a NOP effectively ). */ void vm_page_protect(vm_page_t mem, int prot) { if (prot == VM_PROT_NONE) { if (mem->flags & (PG_WRITEABLE|PG_MAPPED)) { pmap_page_protect(mem, VM_PROT_NONE); vm_page_flag_clear(mem, PG_WRITEABLE|PG_MAPPED); } } else if ((prot == VM_PROT_READ) && (mem->flags & PG_WRITEABLE)) { pmap_page_protect(mem, VM_PROT_READ); vm_page_flag_clear(mem, PG_WRITEABLE); } } /* * vm_page_zero_fill: * * Zero-fill the specified page. * Written as a standard pagein routine, to * be used by the zero-fill object. */ boolean_t vm_page_zero_fill(vm_page_t m) { pmap_zero_page(m); return (TRUE); } /* * vm_page_zero_fill_area: * * Like vm_page_zero_fill but only fill the specified area. */ boolean_t vm_page_zero_fill_area(vm_page_t m, int off, int size) { pmap_zero_page_area(m, off, size); return (TRUE); } /* * vm_page_copy: * * Copy one page to another */ void vm_page_copy(vm_page_t src_m, vm_page_t dest_m) { pmap_copy_page(src_m, dest_m); dest_m->valid = VM_PAGE_BITS_ALL; } /* * vm_page_free: * * Free a page * * The clearing of PG_ZERO is a temporary safety until the code can be * reviewed to determine that PG_ZERO is being properly cleared on * write faults or maps. PG_ZERO was previously cleared in * vm_page_alloc(). */ void vm_page_free(vm_page_t m) { vm_page_flag_clear(m, PG_ZERO); vm_page_free_toq(m); vm_page_zero_idle_wakeup(); } /* * vm_page_free_zero: * * Free a page to the zerod-pages queue */ void vm_page_free_zero(vm_page_t m) { vm_page_flag_set(m, PG_ZERO); vm_page_free_toq(m); } /* * vm_page_sleep_busy: * * Wait until page is no longer PG_BUSY or (if also_m_busy is TRUE) * m->busy is zero. Returns TRUE if it had to sleep ( including if * it almost had to sleep and made temporary spl*() mods), FALSE * otherwise. * * This routine assumes that interrupts can only remove the busy * status from a page, not set the busy status or change it from * PG_BUSY to m->busy or vise versa (which would create a timing * window). */ int vm_page_sleep_busy(vm_page_t m, int also_m_busy, const char *msg) { GIANT_REQUIRED; if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) { int s = splvm(); if ((m->flags & PG_BUSY) || (also_m_busy && m->busy)) { /* * Page is busy. Wait and retry. */ vm_page_flag_set(m, PG_WANTED | PG_REFERENCED); tsleep(m, PVM, msg, 0); } splx(s); return (TRUE); /* not reached */ } return (FALSE); } /* * vm_page_dirty: * * make page all dirty */ void vm_page_dirty(vm_page_t m) { KASSERT(m->queue - m->pc != PQ_CACHE, ("vm_page_dirty: page in cache!")); m->dirty = VM_PAGE_BITS_ALL; } /* * vm_page_undirty: * * Set page to not be dirty. Note: does not clear pmap modify bits */ void vm_page_undirty(vm_page_t m) { m->dirty = 0; } /* * vm_page_insert: [ internal use only ] * * Inserts the given mem entry into the object and object list. * * The pagetables are not updated but will presumably fault the page * in if necessary, or if a kernel page the caller will at some point * enter the page into the kernel's pmap. We are not allowed to block * here so we *can't* do this anyway. * * The object and page must be locked, and must be splhigh. * This routine may not block. */ void vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex) { struct vm_page **bucket; GIANT_REQUIRED; if (m->object != NULL) panic("vm_page_insert: already inserted"); /* * Record the object/offset pair in this page */ m->object = object; m->pindex = pindex; /* * Insert it into the object_object/offset hash table */ bucket = &vm_page_buckets[vm_page_hash(object, pindex)]; mtx_lock_spin(&vm_page_buckets_mtx); m->hnext = *bucket; *bucket = m; mtx_unlock_spin(&vm_page_buckets_mtx); /* * Now link into the object's list of backed pages. */ TAILQ_INSERT_TAIL(&object->memq, m, listq); object->generation++; /* * show that the object has one more resident page. */ object->resident_page_count++; /* * Since we are inserting a new and possibly dirty page, * update the object's OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY flags. */ if (m->flags & PG_WRITEABLE) vm_object_set_writeable_dirty(object); } /* * vm_page_remove: * NOTE: used by device pager as well -wfj * * Removes the given mem entry from the object/offset-page * table and the object page list, but do not invalidate/terminate * the backing store. * * The object and page must be locked, and at splhigh. * The underlying pmap entry (if any) is NOT removed here. * This routine may not block. */ void vm_page_remove(vm_page_t m) { vm_object_t object; vm_page_t *bucket; GIANT_REQUIRED; if (m->object == NULL) return; if ((m->flags & PG_BUSY) == 0) { panic("vm_page_remove: page not busy"); } /* * Basically destroy the page. */ vm_page_wakeup(m); object = m->object; /* * Remove from the object_object/offset hash table. The object * must be on the hash queue, we will panic if it isn't */ bucket = &vm_page_buckets[vm_page_hash(m->object, m->pindex)]; mtx_lock_spin(&vm_page_buckets_mtx); while (*bucket != m) { if (*bucket == NULL) panic("vm_page_remove(): page not found in hash"); bucket = &(*bucket)->hnext; } *bucket = m->hnext; m->hnext = NULL; mtx_unlock_spin(&vm_page_buckets_mtx); /* * Now remove from the object's list of backed pages. */ TAILQ_REMOVE(&object->memq, m, listq); /* * And show that the object has one fewer resident page. */ object->resident_page_count--; object->generation++; m->object = NULL; } /* * vm_page_lookup: * * Returns the page associated with the object/offset * pair specified; if none is found, NULL is returned. * * The object must be locked. No side effects. * This routine may not block. * This is a critical path routine */ vm_page_t vm_page_lookup(vm_object_t object, vm_pindex_t pindex) { vm_page_t m; struct vm_page **bucket; /* * Search the hash table for this object/offset pair */ bucket = &vm_page_buckets[vm_page_hash(object, pindex)]; mtx_lock_spin(&vm_page_buckets_mtx); for (m = *bucket; m != NULL; m = m->hnext) if (m->object == object && m->pindex == pindex) break; mtx_unlock_spin(&vm_page_buckets_mtx); return (m); } /* * vm_page_rename: * * Move the given memory entry from its * current object to the specified target object/offset. * * The object must be locked. * This routine may not block. * * Note: this routine will raise itself to splvm(), the caller need not. * * Note: swap associated with the page must be invalidated by the move. We * have to do this for several reasons: (1) we aren't freeing the * page, (2) we are dirtying the page, (3) the VM system is probably * moving the page from object A to B, and will then later move * the backing store from A to B and we can't have a conflict. * * Note: we *always* dirty the page. It is necessary both for the * fact that we moved it, and because we may be invalidating * swap. If the page is on the cache, we have to deactivate it * or vm_page_dirty() will panic. Dirty pages are not allowed * on the cache. */ void vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex) { int s; s = splvm(); vm_page_lock_queues(); vm_page_remove(m); vm_page_insert(m, new_object, new_pindex); if (m->queue - m->pc == PQ_CACHE) vm_page_deactivate(m); vm_page_dirty(m); vm_page_unlock_queues(); splx(s); } /* * vm_page_select_cache: * * Find a page on the cache queue with color optimization. As pages * might be found, but not applicable, they are deactivated. This * keeps us from using potentially busy cached pages. * * This routine must be called at splvm(). * This routine may not block. */ static vm_page_t vm_page_select_cache(vm_object_t object, vm_pindex_t pindex) { vm_page_t m; mtx_assert(&vm_page_queue_mtx, MA_OWNED); while (TRUE) { m = vm_pageq_find( PQ_CACHE, (pindex + object->pg_color) & PQ_L2_MASK, FALSE ); if (m && ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy || m->hold_count || m->wire_count)) { vm_page_deactivate(m); continue; } return m; } } /* * vm_page_select_free: * * Find a free or zero page, with specified preference. * * This routine must be called at splvm(). * This routine may not block. */ static __inline vm_page_t vm_page_select_free(vm_object_t object, vm_pindex_t pindex, boolean_t prefer_zero) { vm_page_t m; m = vm_pageq_find( PQ_FREE, (pindex + object->pg_color) & PQ_L2_MASK, prefer_zero ); return (m); } /* * vm_page_alloc: * * Allocate and return a memory cell associated * with this VM object/offset pair. * * page_req classes: * VM_ALLOC_NORMAL normal process request * VM_ALLOC_SYSTEM system *really* needs a page * VM_ALLOC_INTERRUPT interrupt time request * VM_ALLOC_ZERO zero page * * This routine may not block. * * Additional special handling is required when called from an * interrupt (VM_ALLOC_INTERRUPT). We are not allowed to mess with * the page cache in this case. */ vm_page_t vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req) { vm_page_t m = NULL; int page_req, s; GIANT_REQUIRED; KASSERT(!vm_page_lookup(object, pindex), ("vm_page_alloc: page already allocated")); page_req = req & VM_ALLOC_CLASS_MASK; /* * The pager is allowed to eat deeper into the free page list. */ if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) { page_req = VM_ALLOC_SYSTEM; }; s = splvm(); loop: mtx_lock_spin(&vm_page_queue_free_mtx); if (cnt.v_free_count > cnt.v_free_reserved) { /* * Allocate from the free queue if there are plenty of pages * in it. */ m = vm_page_select_free(object, pindex, (req & VM_ALLOC_ZERO) != 0); } else if ( (page_req == VM_ALLOC_SYSTEM && cnt.v_cache_count == 0 && cnt.v_free_count > cnt.v_interrupt_free_min) || (page_req == VM_ALLOC_INTERRUPT && cnt.v_free_count > 0) ) { /* * Interrupt or system, dig deeper into the free list. */ m = vm_page_select_free(object, pindex, FALSE); } else if (page_req != VM_ALLOC_INTERRUPT) { mtx_unlock_spin(&vm_page_queue_free_mtx); /* * Allocatable from cache (non-interrupt only). On success, * we must free the page and try again, thus ensuring that * cnt.v_*_free_min counters are replenished. */ vm_page_lock_queues(); if ((m = vm_page_select_cache(object, pindex)) == NULL) { vm_page_unlock_queues(); splx(s); #if defined(DIAGNOSTIC) if (cnt.v_cache_count > 0) printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count); #endif vm_pageout_deficit++; pagedaemon_wakeup(); return (NULL); } KASSERT(m->dirty == 0, ("Found dirty cache page %p", m)); vm_page_busy(m); vm_page_protect(m, VM_PROT_NONE); vm_page_free(m); vm_page_unlock_queues(); goto loop; } else { /* * Not allocatable from cache from interrupt, give up. */ mtx_unlock_spin(&vm_page_queue_free_mtx); splx(s); vm_pageout_deficit++; pagedaemon_wakeup(); return (NULL); } /* * At this point we had better have found a good page. */ KASSERT( m != NULL, ("vm_page_alloc(): missing page on free queue\n") ); /* * Remove from free queue */ vm_pageq_remove_nowakeup(m); /* * Initialize structure. Only the PG_ZERO flag is inherited. */ if (m->flags & PG_ZERO) { vm_page_zero_count--; m->flags = PG_ZERO | PG_BUSY; } else { m->flags = PG_BUSY; } if (req & VM_ALLOC_WIRED) { cnt.v_wire_count++; m->wire_count = 1; } else m->wire_count = 0; m->hold_count = 0; m->act_count = 0; m->busy = 0; m->valid = 0; KASSERT(m->dirty == 0, ("vm_page_alloc: free/cache page %p was dirty", m)); mtx_unlock_spin(&vm_page_queue_free_mtx); /* * vm_page_insert() is safe prior to the splx(). Note also that * inserting a page here does not insert it into the pmap (which * could cause us to block allocating memory). We cannot block * anywhere. */ vm_page_insert(m, object, pindex); /* * Don't wakeup too often - wakeup the pageout daemon when * we would be nearly out of memory. */ if (vm_paging_needed()) pagedaemon_wakeup(); splx(s); return (m); } /* * vm_wait: (also see VM_WAIT macro) * * Block until free pages are available for allocation * - Called in various places before memory allocations. */ void vm_wait(void) { int s; s = splvm(); if (curproc == pageproc) { vm_pageout_pages_needed = 1; tsleep(&vm_pageout_pages_needed, PSWP, "VMWait", 0); } else { if (!vm_pages_needed) { vm_pages_needed = 1; wakeup(&vm_pages_needed); } tsleep(&cnt.v_free_count, PVM, "vmwait", 0); } splx(s); } /* * vm_waitpfault: (also see VM_WAITPFAULT macro) * * Block until free pages are available for allocation * - Called only in vm_fault so that processes page faulting * can be easily tracked. * - Sleeps at a lower priority than vm_wait() so that vm_wait()ing * processes will be able to grab memory first. Do not change * this balance without careful testing first. */ void vm_waitpfault(void) { int s; s = splvm(); if (!vm_pages_needed) { vm_pages_needed = 1; wakeup(&vm_pages_needed); } tsleep(&cnt.v_free_count, PUSER, "pfault", 0); splx(s); } /* * vm_page_activate: * * Put the specified page on the active list (if appropriate). * Ensure that act_count is at least ACT_INIT but do not otherwise * mess with it. * * The page queues must be locked. * This routine may not block. */ void vm_page_activate(vm_page_t m) { int s; GIANT_REQUIRED; s = splvm(); if (m->queue != PQ_ACTIVE) { if ((m->queue - m->pc) == PQ_CACHE) cnt.v_reactivated++; vm_pageq_remove(m); if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) { if (m->act_count < ACT_INIT) m->act_count = ACT_INIT; vm_pageq_enqueue(PQ_ACTIVE, m); } } else { if (m->act_count < ACT_INIT) m->act_count = ACT_INIT; } splx(s); } /* * vm_page_free_wakeup: * * Helper routine for vm_page_free_toq() and vm_page_cache(). This * routine is called when a page has been added to the cache or free * queues. * * This routine may not block. * This routine must be called at splvm() */ static __inline void vm_page_free_wakeup(void) { /* * if pageout daemon needs pages, then tell it that there are * some free. */ if (vm_pageout_pages_needed && cnt.v_cache_count + cnt.v_free_count >= cnt.v_pageout_free_min) { wakeup(&vm_pageout_pages_needed); vm_pageout_pages_needed = 0; } /* * wakeup processes that are waiting on memory if we hit a * high water mark. And wakeup scheduler process if we have * lots of memory. this process will swapin processes. */ if (vm_pages_needed && !vm_page_count_min()) { vm_pages_needed = 0; wakeup(&cnt.v_free_count); } } /* * vm_page_free_toq: * * Returns the given page to the PQ_FREE list, * disassociating it with any VM object. * * Object and page must be locked prior to entry. * This routine may not block. */ void vm_page_free_toq(vm_page_t m) { int s; struct vpgqueues *pq; vm_object_t object = m->object; GIANT_REQUIRED; s = splvm(); cnt.v_tfree++; if (m->busy || ((m->queue - m->pc) == PQ_FREE)) { printf( "vm_page_free: pindex(%lu), busy(%d), PG_BUSY(%d), hold(%d)\n", (u_long)m->pindex, m->busy, (m->flags & PG_BUSY) ? 1 : 0, m->hold_count); if ((m->queue - m->pc) == PQ_FREE) panic("vm_page_free: freeing free page"); else panic("vm_page_free: freeing busy page"); } /* * unqueue, then remove page. Note that we cannot destroy * the page here because we do not want to call the pager's * callback routine until after we've put the page on the * appropriate free queue. */ vm_pageq_remove_nowakeup(m); vm_page_remove(m); /* * If fictitious remove object association and * return, otherwise delay object association removal. */ if ((m->flags & PG_FICTITIOUS) != 0) { splx(s); return; } m->valid = 0; vm_page_undirty(m); if (m->wire_count != 0) { if (m->wire_count > 1) { panic("vm_page_free: invalid wire count (%d), pindex: 0x%lx", m->wire_count, (long)m->pindex); } panic("vm_page_free: freeing wired page\n"); } /* * If we've exhausted the object's resident pages we want to free * it up. */ if (object && (object->type == OBJT_VNODE) && ((object->flags & OBJ_DEAD) == 0) ) { struct vnode *vp = (struct vnode *)object->handle; if (vp && VSHOULDFREE(vp)) vfree(vp); } /* * Clear the UNMANAGED flag when freeing an unmanaged page. */ if (m->flags & PG_UNMANAGED) { m->flags &= ~PG_UNMANAGED; } else { #ifdef __alpha__ pmap_page_is_free(m); #endif } if (m->hold_count != 0) { m->flags &= ~PG_ZERO; m->queue = PQ_HOLD; } else m->queue = PQ_FREE + m->pc; pq = &vm_page_queues[m->queue]; mtx_lock_spin(&vm_page_queue_free_mtx); pq->lcnt++; ++(*pq->cnt); /* * Put zero'd pages on the end ( where we look for zero'd pages * first ) and non-zerod pages at the head. */ if (m->flags & PG_ZERO) { TAILQ_INSERT_TAIL(&pq->pl, m, pageq); ++vm_page_zero_count; } else { TAILQ_INSERT_HEAD(&pq->pl, m, pageq); } mtx_unlock_spin(&vm_page_queue_free_mtx); vm_page_free_wakeup(); splx(s); } /* * vm_page_unmanage: * * Prevent PV management from being done on the page. The page is * removed from the paging queues as if it were wired, and as a * consequence of no longer being managed the pageout daemon will not * touch it (since there is no way to locate the pte mappings for the * page). madvise() calls that mess with the pmap will also no longer * operate on the page. * * Beyond that the page is still reasonably 'normal'. Freeing the page * will clear the flag. * * This routine is used by OBJT_PHYS objects - objects using unswappable * physical memory as backing store rather then swap-backed memory and * will eventually be extended to support 4MB unmanaged physical * mappings. */ void vm_page_unmanage(vm_page_t m) { int s; s = splvm(); mtx_assert(&vm_page_queue_mtx, MA_OWNED); if ((m->flags & PG_UNMANAGED) == 0) { if (m->wire_count == 0) vm_pageq_remove(m); } vm_page_flag_set(m, PG_UNMANAGED); splx(s); } /* * vm_page_wire: * * Mark this page as wired down by yet * another map, removing it from paging queues * as necessary. * * The page queues must be locked. * This routine may not block. */ void vm_page_wire(vm_page_t m) { int s; /* * Only bump the wire statistics if the page is not already wired, * and only unqueue the page if it is on some queue (if it is unmanaged * it is already off the queues). */ s = splvm(); mtx_assert(&vm_page_queue_mtx, MA_OWNED); if (m->wire_count == 0) { if ((m->flags & PG_UNMANAGED) == 0) vm_pageq_remove(m); cnt.v_wire_count++; } m->wire_count++; KASSERT(m->wire_count != 0, ("vm_page_wire: wire_count overflow m=%p", m)); splx(s); vm_page_flag_set(m, PG_MAPPED); } /* * vm_page_unwire: * * Release one wiring of this page, potentially * enabling it to be paged again. * * Many pages placed on the inactive queue should actually go * into the cache, but it is difficult to figure out which. What * we do instead, if the inactive target is well met, is to put * clean pages at the head of the inactive queue instead of the tail. * This will cause them to be moved to the cache more quickly and * if not actively re-referenced, freed more quickly. If we just * stick these pages at the end of the inactive queue, heavy filesystem * meta-data accesses can cause an unnecessary paging load on memory bound * processes. This optimization causes one-time-use metadata to be * reused more quickly. * * BUT, if we are in a low-memory situation we have no choice but to * put clean pages on the cache queue. * * A number of routines use vm_page_unwire() to guarantee that the page * will go into either the inactive or active queues, and will NEVER * be placed in the cache - for example, just after dirtying a page. * dirty pages in the cache are not allowed. * * The page queues must be locked. * This routine may not block. */ void vm_page_unwire(vm_page_t m, int activate) { int s; s = splvm(); mtx_assert(&vm_page_queue_mtx, MA_OWNED); if (m->wire_count > 0) { m->wire_count--; if (m->wire_count == 0) { cnt.v_wire_count--; if (m->flags & PG_UNMANAGED) { ; } else if (activate) vm_pageq_enqueue(PQ_ACTIVE, m); else { vm_page_flag_clear(m, PG_WINATCFLS); vm_pageq_enqueue(PQ_INACTIVE, m); } } } else { panic("vm_page_unwire: invalid wire count: %d\n", m->wire_count); } splx(s); } /* * Move the specified page to the inactive queue. If the page has * any associated swap, the swap is deallocated. * * Normally athead is 0 resulting in LRU operation. athead is set * to 1 if we want this page to be 'as if it were placed in the cache', * except without unmapping it from the process address space. * * This routine may not block. */ static __inline void _vm_page_deactivate(vm_page_t m, int athead) { int s; GIANT_REQUIRED; /* * Ignore if already inactive. */ if (m->queue == PQ_INACTIVE) return; s = splvm(); if (m->wire_count == 0 && (m->flags & PG_UNMANAGED) == 0) { if ((m->queue - m->pc) == PQ_CACHE) cnt.v_reactivated++; vm_page_flag_clear(m, PG_WINATCFLS); vm_pageq_remove(m); if (athead) TAILQ_INSERT_HEAD(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); else TAILQ_INSERT_TAIL(&vm_page_queues[PQ_INACTIVE].pl, m, pageq); m->queue = PQ_INACTIVE; vm_page_queues[PQ_INACTIVE].lcnt++; cnt.v_inactive_count++; } splx(s); } void vm_page_deactivate(vm_page_t m) { _vm_page_deactivate(m, 0); } /* * vm_page_try_to_cache: * * Returns 0 on failure, 1 on success */ int vm_page_try_to_cache(vm_page_t m) { GIANT_REQUIRED; if (m->dirty || m->hold_count || m->busy || m->wire_count || (m->flags & (PG_BUSY|PG_UNMANAGED))) { return (0); } vm_page_test_dirty(m); if (m->dirty) return (0); vm_page_cache(m); return (1); } /* * vm_page_try_to_free() * * Attempt to free the page. If we cannot free it, we do nothing. * 1 is returned on success, 0 on failure. */ int vm_page_try_to_free(vm_page_t m) { if (m->dirty || m->hold_count || m->busy || m->wire_count || (m->flags & (PG_BUSY|PG_UNMANAGED))) { return (0); } vm_page_test_dirty(m); if (m->dirty) return (0); vm_page_busy(m); vm_page_protect(m, VM_PROT_NONE); vm_page_free(m); return (1); } /* * vm_page_cache * * Put the specified page onto the page cache queue (if appropriate). * * This routine may not block. */ void vm_page_cache(vm_page_t m) { int s; GIANT_REQUIRED; if ((m->flags & (PG_BUSY|PG_UNMANAGED)) || m->busy || m->wire_count) { printf("vm_page_cache: attempting to cache busy page\n"); return; } if ((m->queue - m->pc) == PQ_CACHE) return; /* * Remove all pmaps and indicate that the page is not * writeable or mapped. */ vm_page_protect(m, VM_PROT_NONE); if (m->dirty != 0) { panic("vm_page_cache: caching a dirty page, pindex: %ld", (long)m->pindex); } s = splvm(); vm_pageq_remove_nowakeup(m); vm_pageq_enqueue(PQ_CACHE + m->pc, m); vm_page_free_wakeup(); splx(s); } /* * vm_page_dontneed * * Cache, deactivate, or do nothing as appropriate. This routine * is typically used by madvise() MADV_DONTNEED. * * Generally speaking we want to move the page into the cache so * it gets reused quickly. However, this can result in a silly syndrome * due to the page recycling too quickly. Small objects will not be * fully cached. On the otherhand, if we move the page to the inactive * queue we wind up with a problem whereby very large objects * unnecessarily blow away our inactive and cache queues. * * The solution is to move the pages based on a fixed weighting. We * either leave them alone, deactivate them, or move them to the cache, * where moving them to the cache has the highest weighting. * By forcing some pages into other queues we eventually force the * system to balance the queues, potentially recovering other unrelated * space from active. The idea is to not force this to happen too * often. */ void vm_page_dontneed(vm_page_t m) { static int dnweight; int dnw; int head; GIANT_REQUIRED; dnw = ++dnweight; /* * occassionally leave the page alone */ if ((dnw & 0x01F0) == 0 || m->queue == PQ_INACTIVE || m->queue - m->pc == PQ_CACHE ) { if (m->act_count >= ACT_INIT) --m->act_count; return; } if (m->dirty == 0) vm_page_test_dirty(m); if (m->dirty || (dnw & 0x0070) == 0) { /* * Deactivate the page 3 times out of 32. */ head = 0; } else { /* * Cache the page 28 times out of every 32. Note that * the page is deactivated instead of cached, but placed * at the head of the queue instead of the tail. */ head = 1; } _vm_page_deactivate(m, head); } /* * Grab a page, waiting until we are waken up due to the page * changing state. We keep on waiting, if the page continues * to be in the object. If the page doesn't exist, allocate it. * * This routine may block. */ vm_page_t vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags) { vm_page_t m; int s, generation; GIANT_REQUIRED; retrylookup: if ((m = vm_page_lookup(object, pindex)) != NULL) { if (m->busy || (m->flags & PG_BUSY)) { generation = object->generation; s = splvm(); while ((object->generation == generation) && (m->busy || (m->flags & PG_BUSY))) { vm_page_flag_set(m, PG_WANTED | PG_REFERENCED); tsleep(m, PVM, "pgrbwt", 0); if ((allocflags & VM_ALLOC_RETRY) == 0) { splx(s); return NULL; } } splx(s); goto retrylookup; } else { vm_page_busy(m); return m; } } m = vm_page_alloc(object, pindex, allocflags & ~VM_ALLOC_RETRY); if (m == NULL) { VM_WAIT; if ((allocflags & VM_ALLOC_RETRY) == 0) return NULL; goto retrylookup; } return m; } /* * Mapping function for valid bits or for dirty bits in * a page. May not block. * * Inputs are required to range within a page. */ __inline int vm_page_bits(int base, int size) { int first_bit; int last_bit; KASSERT( base + size <= PAGE_SIZE, ("vm_page_bits: illegal base/size %d/%d", base, size) ); if (size == 0) /* handle degenerate case */ return (0); first_bit = base >> DEV_BSHIFT; last_bit = (base + size - 1) >> DEV_BSHIFT; return ((2 << last_bit) - (1 << first_bit)); } /* * vm_page_set_validclean: * * Sets portions of a page valid and clean. The arguments are expected * to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive * of any partial chunks touched by the range. The invalid portion of * such chunks will be zero'd. * * This routine may not block. * * (base + size) must be less then or equal to PAGE_SIZE. */ void vm_page_set_validclean(vm_page_t m, int base, int size) { int pagebits; int frag; int endoff; GIANT_REQUIRED; if (size == 0) /* handle degenerate case */ return; /* * If the base is not DEV_BSIZE aligned and the valid * bit is clear, we have to zero out a portion of the * first block. */ if ((frag = base & ~(DEV_BSIZE - 1)) != base && (m->valid & (1 << (base >> DEV_BSHIFT))) == 0) pmap_zero_page_area(m, frag, base - frag); /* * If the ending offset is not DEV_BSIZE aligned and the * valid bit is clear, we have to zero out a portion of * the last block. */ endoff = base + size; if ((frag = endoff & ~(DEV_BSIZE - 1)) != endoff && (m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0) pmap_zero_page_area(m, endoff, DEV_BSIZE - (endoff & (DEV_BSIZE - 1))); /* * Set valid, clear dirty bits. If validating the entire * page we can safely clear the pmap modify bit. We also * use this opportunity to clear the PG_NOSYNC flag. If a process * takes a write fault on a MAP_NOSYNC memory area the flag will * be set again. * * We set valid bits inclusive of any overlap, but we can only * clear dirty bits for DEV_BSIZE chunks that are fully within * the range. */ pagebits = vm_page_bits(base, size); m->valid |= pagebits; #if 0 /* NOT YET */ if ((frag = base & (DEV_BSIZE - 1)) != 0) { frag = DEV_BSIZE - frag; base += frag; size -= frag; if (size < 0) size = 0; } pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1)); #endif m->dirty &= ~pagebits; if (base == 0 && size == PAGE_SIZE) { pmap_clear_modify(m); vm_page_flag_clear(m, PG_NOSYNC); } } #if 0 void vm_page_set_dirty(vm_page_t m, int base, int size) { m->dirty |= vm_page_bits(base, size); } #endif void vm_page_clear_dirty(vm_page_t m, int base, int size) { GIANT_REQUIRED; m->dirty &= ~vm_page_bits(base, size); } /* * vm_page_set_invalid: * * Invalidates DEV_BSIZE'd chunks within a page. Both the * valid and dirty bits for the effected areas are cleared. * * May not block. */ void vm_page_set_invalid(vm_page_t m, int base, int size) { int bits; GIANT_REQUIRED; bits = vm_page_bits(base, size); m->valid &= ~bits; m->dirty &= ~bits; m->object->generation++; } /* * vm_page_zero_invalid() * * The kernel assumes that the invalid portions of a page contain * garbage, but such pages can be mapped into memory by user code. * When this occurs, we must zero out the non-valid portions of the * page so user code sees what it expects. * * Pages are most often semi-valid when the end of a file is mapped * into memory and the file's size is not page aligned. */ void vm_page_zero_invalid(vm_page_t m, boolean_t setvalid) { int b; int i; /* * Scan the valid bits looking for invalid sections that * must be zerod. Invalid sub-DEV_BSIZE'd areas ( where the * valid bit may be set ) have already been zerod by * vm_page_set_validclean(). */ for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) { if (i == (PAGE_SIZE / DEV_BSIZE) || (m->valid & (1 << i)) ) { if (i > b) { pmap_zero_page_area(m, b << DEV_BSHIFT, (i - b) << DEV_BSHIFT); } b = i + 1; } } /* * setvalid is TRUE when we can safely set the zero'd areas * as being valid. We can do this if there are no cache consistancy * issues. e.g. it is ok to do with UFS, but not ok to do with NFS. */ if (setvalid) m->valid = VM_PAGE_BITS_ALL; } /* * vm_page_is_valid: * * Is (partial) page valid? Note that the case where size == 0 * will return FALSE in the degenerate case where the page is * entirely invalid, and TRUE otherwise. * * May not block. */ int vm_page_is_valid(vm_page_t m, int base, int size) { int bits = vm_page_bits(base, size); if (m->valid && ((m->valid & bits) == bits)) return 1; else return 0; } /* * update dirty bits from pmap/mmu. May not block. */ void vm_page_test_dirty(vm_page_t m) { if ((m->dirty != VM_PAGE_BITS_ALL) && pmap_is_modified(m)) { vm_page_dirty(m); } } int so_zerocp_fullpage = 0; void vm_page_cowfault(vm_page_t m) { vm_page_t mnew; vm_object_t object; vm_pindex_t pindex; object = m->object; pindex = m->pindex; vm_page_busy(m); retry_alloc: vm_page_remove(m); mnew = vm_page_alloc(object, pindex, VM_ALLOC_NORMAL); if (mnew == NULL) { vm_page_insert(m, object, pindex); VM_WAIT; goto retry_alloc; } if (m->cow == 0) { /* * check to see if we raced with an xmit complete when * waiting to allocate a page. If so, put things back * the way they were */ vm_page_busy(mnew); vm_page_free(mnew); vm_page_insert(m, object, pindex); } else { /* clear COW & copy page */ if (so_zerocp_fullpage) { mnew->valid = VM_PAGE_BITS_ALL; } else { vm_page_copy(m, mnew); } vm_page_dirty(mnew); vm_page_flag_clear(mnew, PG_BUSY); } } void vm_page_cowclear(vm_page_t m) { /* XXX KDM find out if giant is required here. */ GIANT_REQUIRED; if (m->cow) { atomic_subtract_int(&m->cow, 1); /* * let vm_fault add back write permission lazily */ } /* * sf_buf_free() will free the page, so we needn't do it here */ } void vm_page_cowsetup(vm_page_t m) { /* XXX KDM find out if giant is required here */ GIANT_REQUIRED; atomic_add_int(&m->cow, 1); vm_page_protect(m, VM_PROT_READ); } #include "opt_ddb.h" #ifdef DDB #include #include DB_SHOW_COMMAND(page, vm_page_print_page_info) { db_printf("cnt.v_free_count: %d\n", cnt.v_free_count); db_printf("cnt.v_cache_count: %d\n", cnt.v_cache_count); db_printf("cnt.v_inactive_count: %d\n", cnt.v_inactive_count); db_printf("cnt.v_active_count: %d\n", cnt.v_active_count); db_printf("cnt.v_wire_count: %d\n", cnt.v_wire_count); db_printf("cnt.v_free_reserved: %d\n", cnt.v_free_reserved); db_printf("cnt.v_free_min: %d\n", cnt.v_free_min); db_printf("cnt.v_free_target: %d\n", cnt.v_free_target); db_printf("cnt.v_cache_min: %d\n", cnt.v_cache_min); db_printf("cnt.v_inactive_target: %d\n", cnt.v_inactive_target); } DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info) { int i; db_printf("PQ_FREE:"); for (i = 0; i < PQ_L2_SIZE; i++) { db_printf(" %d", vm_page_queues[PQ_FREE + i].lcnt); } db_printf("\n"); db_printf("PQ_CACHE:"); for (i = 0; i < PQ_L2_SIZE; i++) { db_printf(" %d", vm_page_queues[PQ_CACHE + i].lcnt); } db_printf("\n"); db_printf("PQ_ACTIVE: %d, PQ_INACTIVE: %d\n", vm_page_queues[PQ_ACTIVE].lcnt, vm_page_queues[PQ_INACTIVE].lcnt); } #endif /* DDB */