Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/mm/vmscan.c b/mm/vmscan.c
new file mode 100644
index 0000000..4003c05
--- /dev/null
+++ b/mm/vmscan.c
@@ -0,0 +1,1311 @@
+/*
+ * linux/mm/vmscan.c
+ *
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ *
+ * Swap reorganised 29.12.95, Stephen Tweedie.
+ * kswapd added: 7.1.96 sct
+ * Removed kswapd_ctl limits, and swap out as many pages as needed
+ * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
+ * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
+ * Multiqueue VM started 5.8.00, Rik van Riel.
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/highmem.h>
+#include <linux/file.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h> /* for try_to_release_page(),
+ buffer_heads_over_limit */
+#include <linux/mm_inline.h>
+#include <linux/pagevec.h>
+#include <linux/backing-dev.h>
+#include <linux/rmap.h>
+#include <linux/topology.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/notifier.h>
+#include <linux/rwsem.h>
+
+#include <asm/tlbflush.h>
+#include <asm/div64.h>
+
+#include <linux/swapops.h>
+
+/* possible outcome of pageout() */
+typedef enum {
+ /* failed to write page out, page is locked */
+ PAGE_KEEP,
+ /* move page to the active list, page is locked */
+ PAGE_ACTIVATE,
+ /* page has been sent to the disk successfully, page is unlocked */
+ PAGE_SUCCESS,
+ /* page is clean and locked */
+ PAGE_CLEAN,
+} pageout_t;
+
+struct scan_control {
+ /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
+ unsigned long nr_to_scan;
+
+ /* Incremented by the number of inactive pages that were scanned */
+ unsigned long nr_scanned;
+
+ /* Incremented by the number of pages reclaimed */
+ unsigned long nr_reclaimed;
+
+ unsigned long nr_mapped; /* From page_state */
+
+ /* How many pages shrink_cache() should reclaim */
+ int nr_to_reclaim;
+
+ /* Ask shrink_caches, or shrink_zone to scan at this priority */
+ unsigned int priority;
+
+ /* This context's GFP mask */
+ unsigned int gfp_mask;
+
+ int may_writepage;
+
+ /* This context's SWAP_CLUSTER_MAX. If freeing memory for
+ * suspend, we effectively ignore SWAP_CLUSTER_MAX.
+ * In this context, it doesn't matter that we scan the
+ * whole list at once. */
+ int swap_cluster_max;
+};
+
+/*
+ * The list of shrinker callbacks used by to apply pressure to
+ * ageable caches.
+ */
+struct shrinker {
+ shrinker_t shrinker;
+ struct list_head list;
+ int seeks; /* seeks to recreate an obj */
+ long nr; /* objs pending delete */
+};
+
+#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
+
+#ifdef ARCH_HAS_PREFETCH
+#define prefetch_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetch(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+#ifdef ARCH_HAS_PREFETCHW
+#define prefetchw_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetchw(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+/*
+ * From 0 .. 100. Higher means more swappy.
+ */
+int vm_swappiness = 60;
+static long total_memory;
+
+static LIST_HEAD(shrinker_list);
+static DECLARE_RWSEM(shrinker_rwsem);
+
+/*
+ * Add a shrinker callback to be called from the vm
+ */
+struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
+{
+ struct shrinker *shrinker;
+
+ shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
+ if (shrinker) {
+ shrinker->shrinker = theshrinker;
+ shrinker->seeks = seeks;
+ shrinker->nr = 0;
+ down_write(&shrinker_rwsem);
+ list_add_tail(&shrinker->list, &shrinker_list);
+ up_write(&shrinker_rwsem);
+ }
+ return shrinker;
+}
+EXPORT_SYMBOL(set_shrinker);
+
+/*
+ * Remove one
+ */
+void remove_shrinker(struct shrinker *shrinker)
+{
+ down_write(&shrinker_rwsem);
+ list_del(&shrinker->list);
+ up_write(&shrinker_rwsem);
+ kfree(shrinker);
+}
+EXPORT_SYMBOL(remove_shrinker);
+
+#define SHRINK_BATCH 128
+/*
+ * Call the shrink functions to age shrinkable caches
+ *
+ * Here we assume it costs one seek to replace a lru page and that it also
+ * takes a seek to recreate a cache object. With this in mind we age equal
+ * percentages of the lru and ageable caches. This should balance the seeks
+ * generated by these structures.
+ *
+ * If the vm encounted mapped pages on the LRU it increase the pressure on
+ * slab to avoid swapping.
+ *
+ * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
+ *
+ * `lru_pages' represents the number of on-LRU pages in all the zones which
+ * are eligible for the caller's allocation attempt. It is used for balancing
+ * slab reclaim versus page reclaim.
+ */
+static int shrink_slab(unsigned long scanned, unsigned int gfp_mask,
+ unsigned long lru_pages)
+{
+ struct shrinker *shrinker;
+
+ if (scanned == 0)
+ scanned = SWAP_CLUSTER_MAX;
+
+ if (!down_read_trylock(&shrinker_rwsem))
+ return 0;
+
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ unsigned long long delta;
+ unsigned long total_scan;
+
+ delta = (4 * scanned) / shrinker->seeks;
+ delta *= (*shrinker->shrinker)(0, gfp_mask);
+ do_div(delta, lru_pages + 1);
+ shrinker->nr += delta;
+ if (shrinker->nr < 0)
+ shrinker->nr = LONG_MAX; /* It wrapped! */
+
+ total_scan = shrinker->nr;
+ shrinker->nr = 0;
+
+ while (total_scan >= SHRINK_BATCH) {
+ long this_scan = SHRINK_BATCH;
+ int shrink_ret;
+
+ shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
+ if (shrink_ret == -1)
+ break;
+ mod_page_state(slabs_scanned, this_scan);
+ total_scan -= this_scan;
+
+ cond_resched();
+ }
+
+ shrinker->nr += total_scan;
+ }
+ up_read(&shrinker_rwsem);
+ return 0;
+}
+
+/* Called without lock on whether page is mapped, so answer is unstable */
+static inline int page_mapping_inuse(struct page *page)
+{
+ struct address_space *mapping;
+
+ /* Page is in somebody's page tables. */
+ if (page_mapped(page))
+ return 1;
+
+ /* Be more reluctant to reclaim swapcache than pagecache */
+ if (PageSwapCache(page))
+ return 1;
+
+ mapping = page_mapping(page);
+ if (!mapping)
+ return 0;
+
+ /* File is mmap'd by somebody? */
+ return mapping_mapped(mapping);
+}
+
+static inline int is_page_cache_freeable(struct page *page)
+{
+ return page_count(page) - !!PagePrivate(page) == 2;
+}
+
+static int may_write_to_queue(struct backing_dev_info *bdi)
+{
+ if (current_is_kswapd())
+ return 1;
+ if (current_is_pdflush()) /* This is unlikely, but why not... */
+ return 1;
+ if (!bdi_write_congested(bdi))
+ return 1;
+ if (bdi == current->backing_dev_info)
+ return 1;
+ return 0;
+}
+
+/*
+ * We detected a synchronous write error writing a page out. Probably
+ * -ENOSPC. We need to propagate that into the address_space for a subsequent
+ * fsync(), msync() or close().
+ *
+ * The tricky part is that after writepage we cannot touch the mapping: nothing
+ * prevents it from being freed up. But we have a ref on the page and once
+ * that page is locked, the mapping is pinned.
+ *
+ * We're allowed to run sleeping lock_page() here because we know the caller has
+ * __GFP_FS.
+ */
+static void handle_write_error(struct address_space *mapping,
+ struct page *page, int error)
+{
+ lock_page(page);
+ if (page_mapping(page) == mapping) {
+ if (error == -ENOSPC)
+ set_bit(AS_ENOSPC, &mapping->flags);
+ else
+ set_bit(AS_EIO, &mapping->flags);
+ }
+ unlock_page(page);
+}
+
+/*
+ * pageout is called by shrink_list() for each dirty page. Calls ->writepage().
+ */
+static pageout_t pageout(struct page *page, struct address_space *mapping)
+{
+ /*
+ * If the page is dirty, only perform writeback if that write
+ * will be non-blocking. To prevent this allocation from being
+ * stalled by pagecache activity. But note that there may be
+ * stalls if we need to run get_block(). We could test
+ * PagePrivate for that.
+ *
+ * If this process is currently in generic_file_write() against
+ * this page's queue, we can perform writeback even if that
+ * will block.
+ *
+ * If the page is swapcache, write it back even if that would
+ * block, for some throttling. This happens by accident, because
+ * swap_backing_dev_info is bust: it doesn't reflect the
+ * congestion state of the swapdevs. Easy to fix, if needed.
+ * See swapfile.c:page_queue_congested().
+ */
+ if (!is_page_cache_freeable(page))
+ return PAGE_KEEP;
+ if (!mapping) {
+ /*
+ * Some data journaling orphaned pages can have
+ * page->mapping == NULL while being dirty with clean buffers.
+ */
+ if (PageDirty(page) && PagePrivate(page)) {
+ if (try_to_free_buffers(page)) {
+ ClearPageDirty(page);
+ printk("%s: orphaned page\n", __FUNCTION__);
+ return PAGE_CLEAN;
+ }
+ }
+ return PAGE_KEEP;
+ }
+ if (mapping->a_ops->writepage == NULL)
+ return PAGE_ACTIVATE;
+ if (!may_write_to_queue(mapping->backing_dev_info))
+ return PAGE_KEEP;
+
+ if (clear_page_dirty_for_io(page)) {
+ int res;
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_to_write = SWAP_CLUSTER_MAX,
+ .nonblocking = 1,
+ .for_reclaim = 1,
+ };
+
+ SetPageReclaim(page);
+ res = mapping->a_ops->writepage(page, &wbc);
+ if (res < 0)
+ handle_write_error(mapping, page, res);
+ if (res == WRITEPAGE_ACTIVATE) {
+ ClearPageReclaim(page);
+ return PAGE_ACTIVATE;
+ }
+ if (!PageWriteback(page)) {
+ /* synchronous write or broken a_ops? */
+ ClearPageReclaim(page);
+ }
+
+ return PAGE_SUCCESS;
+ }
+
+ return PAGE_CLEAN;
+}
+
+/*
+ * shrink_list adds the number of reclaimed pages to sc->nr_reclaimed
+ */
+static int shrink_list(struct list_head *page_list, struct scan_control *sc)
+{
+ LIST_HEAD(ret_pages);
+ struct pagevec freed_pvec;
+ int pgactivate = 0;
+ int reclaimed = 0;
+
+ cond_resched();
+
+ pagevec_init(&freed_pvec, 1);
+ while (!list_empty(page_list)) {
+ struct address_space *mapping;
+ struct page *page;
+ int may_enter_fs;
+ int referenced;
+
+ cond_resched();
+
+ page = lru_to_page(page_list);
+ list_del(&page->lru);
+
+ if (TestSetPageLocked(page))
+ goto keep;
+
+ BUG_ON(PageActive(page));
+
+ sc->nr_scanned++;
+ /* Double the slab pressure for mapped and swapcache pages */
+ if (page_mapped(page) || PageSwapCache(page))
+ sc->nr_scanned++;
+
+ if (PageWriteback(page))
+ goto keep_locked;
+
+ referenced = page_referenced(page, 1, sc->priority <= 0);
+ /* In active use or really unfreeable? Activate it. */
+ if (referenced && page_mapping_inuse(page))
+ goto activate_locked;
+
+#ifdef CONFIG_SWAP
+ /*
+ * Anonymous process memory has backing store?
+ * Try to allocate it some swap space here.
+ */
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ if (!add_to_swap(page))
+ goto activate_locked;
+ }
+#endif /* CONFIG_SWAP */
+
+ mapping = page_mapping(page);
+ may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+ (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+
+ /*
+ * The page is mapped into the page tables of one or more
+ * processes. Try to unmap it here.
+ */
+ if (page_mapped(page) && mapping) {
+ switch (try_to_unmap(page)) {
+ case SWAP_FAIL:
+ goto activate_locked;
+ case SWAP_AGAIN:
+ goto keep_locked;
+ case SWAP_SUCCESS:
+ ; /* try to free the page below */
+ }
+ }
+
+ if (PageDirty(page)) {
+ if (referenced)
+ goto keep_locked;
+ if (!may_enter_fs)
+ goto keep_locked;
+ if (laptop_mode && !sc->may_writepage)
+ goto keep_locked;
+
+ /* Page is dirty, try to write it out here */
+ switch(pageout(page, mapping)) {
+ case PAGE_KEEP:
+ goto keep_locked;
+ case PAGE_ACTIVATE:
+ goto activate_locked;
+ case PAGE_SUCCESS:
+ if (PageWriteback(page) || PageDirty(page))
+ goto keep;
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the page.
+ */
+ if (TestSetPageLocked(page))
+ goto keep;
+ if (PageDirty(page) || PageWriteback(page))
+ goto keep_locked;
+ mapping = page_mapping(page);
+ case PAGE_CLEAN:
+ ; /* try to free the page below */
+ }
+ }
+
+ /*
+ * If the page has buffers, try to free the buffer mappings
+ * associated with this page. If we succeed we try to free
+ * the page as well.
+ *
+ * We do this even if the page is PageDirty().
+ * try_to_release_page() does not perform I/O, but it is
+ * possible for a page to have PageDirty set, but it is actually
+ * clean (all its buffers are clean). This happens if the
+ * buffers were written out directly, with submit_bh(). ext3
+ * will do this, as well as the blockdev mapping.
+ * try_to_release_page() will discover that cleanness and will
+ * drop the buffers and mark the page clean - it can be freed.
+ *
+ * Rarely, pages can have buffers and no ->mapping. These are
+ * the pages which were not successfully invalidated in
+ * truncate_complete_page(). We try to drop those buffers here
+ * and if that worked, and the page is no longer mapped into
+ * process address space (page_count == 1) it can be freed.
+ * Otherwise, leave the page on the LRU so it is swappable.
+ */
+ if (PagePrivate(page)) {
+ if (!try_to_release_page(page, sc->gfp_mask))
+ goto activate_locked;
+ if (!mapping && page_count(page) == 1)
+ goto free_it;
+ }
+
+ if (!mapping)
+ goto keep_locked; /* truncate got there first */
+
+ write_lock_irq(&mapping->tree_lock);
+
+ /*
+ * The non-racy check for busy page. It is critical to check
+ * PageDirty _after_ making sure that the page is freeable and
+ * not in use by anybody. (pagecache + us == 2)
+ */
+ if (page_count(page) != 2 || PageDirty(page)) {
+ write_unlock_irq(&mapping->tree_lock);
+ goto keep_locked;
+ }
+
+#ifdef CONFIG_SWAP
+ if (PageSwapCache(page)) {
+ swp_entry_t swap = { .val = page->private };
+ __delete_from_swap_cache(page);
+ write_unlock_irq(&mapping->tree_lock);
+ swap_free(swap);
+ __put_page(page); /* The pagecache ref */
+ goto free_it;
+ }
+#endif /* CONFIG_SWAP */
+
+ __remove_from_page_cache(page);
+ write_unlock_irq(&mapping->tree_lock);
+ __put_page(page);
+
+free_it:
+ unlock_page(page);
+ reclaimed++;
+ if (!pagevec_add(&freed_pvec, page))
+ __pagevec_release_nonlru(&freed_pvec);
+ continue;
+
+activate_locked:
+ SetPageActive(page);
+ pgactivate++;
+keep_locked:
+ unlock_page(page);
+keep:
+ list_add(&page->lru, &ret_pages);
+ BUG_ON(PageLRU(page));
+ }
+ list_splice(&ret_pages, page_list);
+ if (pagevec_count(&freed_pvec))
+ __pagevec_release_nonlru(&freed_pvec);
+ mod_page_state(pgactivate, pgactivate);
+ sc->nr_reclaimed += reclaimed;
+ return reclaimed;
+}
+
+/*
+ * zone->lru_lock is heavily contended. Some of the functions that
+ * shrink the lists perform better by taking out a batch of pages
+ * and working on them outside the LRU lock.
+ *
+ * For pagecache intensive workloads, this function is the hottest
+ * spot in the kernel (apart from copy_*_user functions).
+ *
+ * Appropriate locks must be held before calling this function.
+ *
+ * @nr_to_scan: The number of pages to look through on the list.
+ * @src: The LRU list to pull pages off.
+ * @dst: The temp list to put pages on to.
+ * @scanned: The number of pages that were scanned.
+ *
+ * returns how many pages were moved onto *@dst.
+ */
+static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
+ struct list_head *dst, int *scanned)
+{
+ int nr_taken = 0;
+ struct page *page;
+ int scan = 0;
+
+ while (scan++ < nr_to_scan && !list_empty(src)) {
+ page = lru_to_page(src);
+ prefetchw_prev_lru_page(page, src, flags);
+
+ if (!TestClearPageLRU(page))
+ BUG();
+ list_del(&page->lru);
+ if (get_page_testone(page)) {
+ /*
+ * It is being freed elsewhere
+ */
+ __put_page(page);
+ SetPageLRU(page);
+ list_add(&page->lru, src);
+ continue;
+ } else {
+ list_add(&page->lru, dst);
+ nr_taken++;
+ }
+ }
+
+ *scanned = scan;
+ return nr_taken;
+}
+
+/*
+ * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
+ */
+static void shrink_cache(struct zone *zone, struct scan_control *sc)
+{
+ LIST_HEAD(page_list);
+ struct pagevec pvec;
+ int max_scan = sc->nr_to_scan;
+
+ pagevec_init(&pvec, 1);
+
+ lru_add_drain();
+ spin_lock_irq(&zone->lru_lock);
+ while (max_scan > 0) {
+ struct page *page;
+ int nr_taken;
+ int nr_scan;
+ int nr_freed;
+
+ nr_taken = isolate_lru_pages(sc->swap_cluster_max,
+ &zone->inactive_list,
+ &page_list, &nr_scan);
+ zone->nr_inactive -= nr_taken;
+ zone->pages_scanned += nr_scan;
+ spin_unlock_irq(&zone->lru_lock);
+
+ if (nr_taken == 0)
+ goto done;
+
+ max_scan -= nr_scan;
+ if (current_is_kswapd())
+ mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
+ else
+ mod_page_state_zone(zone, pgscan_direct, nr_scan);
+ nr_freed = shrink_list(&page_list, sc);
+ if (current_is_kswapd())
+ mod_page_state(kswapd_steal, nr_freed);
+ mod_page_state_zone(zone, pgsteal, nr_freed);
+ sc->nr_to_reclaim -= nr_freed;
+
+ spin_lock_irq(&zone->lru_lock);
+ /*
+ * Put back any unfreeable pages.
+ */
+ while (!list_empty(&page_list)) {
+ page = lru_to_page(&page_list);
+ if (TestSetPageLRU(page))
+ BUG();
+ list_del(&page->lru);
+ if (PageActive(page))
+ add_page_to_active_list(zone, page);
+ else
+ add_page_to_inactive_list(zone, page);
+ if (!pagevec_add(&pvec, page)) {
+ spin_unlock_irq(&zone->lru_lock);
+ __pagevec_release(&pvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+ }
+ }
+ spin_unlock_irq(&zone->lru_lock);
+done:
+ pagevec_release(&pvec);
+}
+
+/*
+ * This moves pages from the active list to the inactive list.
+ *
+ * We move them the other way if the page is referenced by one or more
+ * processes, from rmap.
+ *
+ * If the pages are mostly unmapped, the processing is fast and it is
+ * appropriate to hold zone->lru_lock across the whole operation. But if
+ * the pages are mapped, the processing is slow (page_referenced()) so we
+ * should drop zone->lru_lock around each page. It's impossible to balance
+ * this, so instead we remove the pages from the LRU while processing them.
+ * It is safe to rely on PG_active against the non-LRU pages in here because
+ * nobody will play with that bit on a non-LRU page.
+ *
+ * The downside is that we have to touch page->_count against each page.
+ * But we had to alter page->flags anyway.
+ */
+static void
+refill_inactive_zone(struct zone *zone, struct scan_control *sc)
+{
+ int pgmoved;
+ int pgdeactivate = 0;
+ int pgscanned;
+ int nr_pages = sc->nr_to_scan;
+ LIST_HEAD(l_hold); /* The pages which were snipped off */
+ LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */
+ LIST_HEAD(l_active); /* Pages to go onto the active_list */
+ struct page *page;
+ struct pagevec pvec;
+ int reclaim_mapped = 0;
+ long mapped_ratio;
+ long distress;
+ long swap_tendency;
+
+ lru_add_drain();
+ spin_lock_irq(&zone->lru_lock);
+ pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
+ &l_hold, &pgscanned);
+ zone->pages_scanned += pgscanned;
+ zone->nr_active -= pgmoved;
+ spin_unlock_irq(&zone->lru_lock);
+
+ /*
+ * `distress' is a measure of how much trouble we're having reclaiming
+ * pages. 0 -> no problems. 100 -> great trouble.
+ */
+ distress = 100 >> zone->prev_priority;
+
+ /*
+ * The point of this algorithm is to decide when to start reclaiming
+ * mapped memory instead of just pagecache. Work out how much memory
+ * is mapped.
+ */
+ mapped_ratio = (sc->nr_mapped * 100) / total_memory;
+
+ /*
+ * Now decide how much we really want to unmap some pages. The mapped
+ * ratio is downgraded - just because there's a lot of mapped memory
+ * doesn't necessarily mean that page reclaim isn't succeeding.
+ *
+ * The distress ratio is important - we don't want to start going oom.
+ *
+ * A 100% value of vm_swappiness overrides this algorithm altogether.
+ */
+ swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
+
+ /*
+ * Now use this metric to decide whether to start moving mapped memory
+ * onto the inactive list.
+ */
+ if (swap_tendency >= 100)
+ reclaim_mapped = 1;
+
+ while (!list_empty(&l_hold)) {
+ cond_resched();
+ page = lru_to_page(&l_hold);
+ list_del(&page->lru);
+ if (page_mapped(page)) {
+ if (!reclaim_mapped ||
+ (total_swap_pages == 0 && PageAnon(page)) ||
+ page_referenced(page, 0, sc->priority <= 0)) {
+ list_add(&page->lru, &l_active);
+ continue;
+ }
+ }
+ list_add(&page->lru, &l_inactive);
+ }
+
+ pagevec_init(&pvec, 1);
+ pgmoved = 0;
+ spin_lock_irq(&zone->lru_lock);
+ while (!list_empty(&l_inactive)) {
+ page = lru_to_page(&l_inactive);
+ prefetchw_prev_lru_page(page, &l_inactive, flags);
+ if (TestSetPageLRU(page))
+ BUG();
+ if (!TestClearPageActive(page))
+ BUG();
+ list_move(&page->lru, &zone->inactive_list);
+ pgmoved++;
+ if (!pagevec_add(&pvec, page)) {
+ zone->nr_inactive += pgmoved;
+ spin_unlock_irq(&zone->lru_lock);
+ pgdeactivate += pgmoved;
+ pgmoved = 0;
+ if (buffer_heads_over_limit)
+ pagevec_strip(&pvec);
+ __pagevec_release(&pvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+ }
+ zone->nr_inactive += pgmoved;
+ pgdeactivate += pgmoved;
+ if (buffer_heads_over_limit) {
+ spin_unlock_irq(&zone->lru_lock);
+ pagevec_strip(&pvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+
+ pgmoved = 0;
+ while (!list_empty(&l_active)) {
+ page = lru_to_page(&l_active);
+ prefetchw_prev_lru_page(page, &l_active, flags);
+ if (TestSetPageLRU(page))
+ BUG();
+ BUG_ON(!PageActive(page));
+ list_move(&page->lru, &zone->active_list);
+ pgmoved++;
+ if (!pagevec_add(&pvec, page)) {
+ zone->nr_active += pgmoved;
+ pgmoved = 0;
+ spin_unlock_irq(&zone->lru_lock);
+ __pagevec_release(&pvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+ }
+ zone->nr_active += pgmoved;
+ spin_unlock_irq(&zone->lru_lock);
+ pagevec_release(&pvec);
+
+ mod_page_state_zone(zone, pgrefill, pgscanned);
+ mod_page_state(pgdeactivate, pgdeactivate);
+}
+
+/*
+ * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
+ */
+static void
+shrink_zone(struct zone *zone, struct scan_control *sc)
+{
+ unsigned long nr_active;
+ unsigned long nr_inactive;
+
+ /*
+ * Add one to `nr_to_scan' just to make sure that the kernel will
+ * slowly sift through the active list.
+ */
+ zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
+ nr_active = zone->nr_scan_active;
+ if (nr_active >= sc->swap_cluster_max)
+ zone->nr_scan_active = 0;
+ else
+ nr_active = 0;
+
+ zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
+ nr_inactive = zone->nr_scan_inactive;
+ if (nr_inactive >= sc->swap_cluster_max)
+ zone->nr_scan_inactive = 0;
+ else
+ nr_inactive = 0;
+
+ sc->nr_to_reclaim = sc->swap_cluster_max;
+
+ while (nr_active || nr_inactive) {
+ if (nr_active) {
+ sc->nr_to_scan = min(nr_active,
+ (unsigned long)sc->swap_cluster_max);
+ nr_active -= sc->nr_to_scan;
+ refill_inactive_zone(zone, sc);
+ }
+
+ if (nr_inactive) {
+ sc->nr_to_scan = min(nr_inactive,
+ (unsigned long)sc->swap_cluster_max);
+ nr_inactive -= sc->nr_to_scan;
+ shrink_cache(zone, sc);
+ if (sc->nr_to_reclaim <= 0)
+ break;
+ }
+ }
+
+ throttle_vm_writeout();
+}
+
+/*
+ * This is the direct reclaim path, for page-allocating processes. We only
+ * try to reclaim pages from zones which will satisfy the caller's allocation
+ * request.
+ *
+ * We reclaim from a zone even if that zone is over pages_high. Because:
+ * a) The caller may be trying to free *extra* pages to satisfy a higher-order
+ * allocation or
+ * b) The zones may be over pages_high but they must go *over* pages_high to
+ * satisfy the `incremental min' zone defense algorithm.
+ *
+ * Returns the number of reclaimed pages.
+ *
+ * If a zone is deemed to be full of pinned pages then just give it a light
+ * scan then give up on it.
+ */
+static void
+shrink_caches(struct zone **zones, struct scan_control *sc)
+{
+ int i;
+
+ for (i = 0; zones[i] != NULL; i++) {
+ struct zone *zone = zones[i];
+
+ if (zone->present_pages == 0)
+ continue;
+
+ if (!cpuset_zone_allowed(zone))
+ continue;
+
+ zone->temp_priority = sc->priority;
+ if (zone->prev_priority > sc->priority)
+ zone->prev_priority = sc->priority;
+
+ if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
+ continue; /* Let kswapd poll it */
+
+ shrink_zone(zone, sc);
+ }
+}
+
+/*
+ * This is the main entry point to direct page reclaim.
+ *
+ * If a full scan of the inactive list fails to free enough memory then we
+ * are "out of memory" and something needs to be killed.
+ *
+ * If the caller is !__GFP_FS then the probability of a failure is reasonably
+ * high - the zone may be full of dirty or under-writeback pages, which this
+ * caller can't do much about. We kick pdflush and take explicit naps in the
+ * hope that some of these pages can be written. But if the allocating task
+ * holds filesystem locks which prevent writeout this might not work, and the
+ * allocation attempt will fail.
+ */
+int try_to_free_pages(struct zone **zones,
+ unsigned int gfp_mask, unsigned int order)
+{
+ int priority;
+ int ret = 0;
+ int total_scanned = 0, total_reclaimed = 0;
+ struct reclaim_state *reclaim_state = current->reclaim_state;
+ struct scan_control sc;
+ unsigned long lru_pages = 0;
+ int i;
+
+ sc.gfp_mask = gfp_mask;
+ sc.may_writepage = 0;
+
+ inc_page_state(allocstall);
+
+ for (i = 0; zones[i] != NULL; i++) {
+ struct zone *zone = zones[i];
+
+ if (!cpuset_zone_allowed(zone))
+ continue;
+
+ zone->temp_priority = DEF_PRIORITY;
+ lru_pages += zone->nr_active + zone->nr_inactive;
+ }
+
+ for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+ sc.nr_mapped = read_page_state(nr_mapped);
+ sc.nr_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.priority = priority;
+ sc.swap_cluster_max = SWAP_CLUSTER_MAX;
+ shrink_caches(zones, &sc);
+ shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
+ if (reclaim_state) {
+ sc.nr_reclaimed += reclaim_state->reclaimed_slab;
+ reclaim_state->reclaimed_slab = 0;
+ }
+ total_scanned += sc.nr_scanned;
+ total_reclaimed += sc.nr_reclaimed;
+ if (total_reclaimed >= sc.swap_cluster_max) {
+ ret = 1;
+ goto out;
+ }
+
+ /*
+ * Try to write back as many pages as we just scanned. This
+ * tends to cause slow streaming writers to write data to the
+ * disk smoothly, at the dirtying rate, which is nice. But
+ * that's undesirable in laptop mode, where we *want* lumpy
+ * writeout. So in laptop mode, write out the whole world.
+ */
+ if (total_scanned > sc.swap_cluster_max + sc.swap_cluster_max/2) {
+ wakeup_bdflush(laptop_mode ? 0 : total_scanned);
+ sc.may_writepage = 1;
+ }
+
+ /* Take a nap, wait for some writeback to complete */
+ if (sc.nr_scanned && priority < DEF_PRIORITY - 2)
+ blk_congestion_wait(WRITE, HZ/10);
+ }
+out:
+ for (i = 0; zones[i] != 0; i++) {
+ struct zone *zone = zones[i];
+
+ if (!cpuset_zone_allowed(zone))
+ continue;
+
+ zone->prev_priority = zone->temp_priority;
+ }
+ return ret;
+}
+
+/*
+ * For kswapd, balance_pgdat() will work across all this node's zones until
+ * they are all at pages_high.
+ *
+ * If `nr_pages' is non-zero then it is the number of pages which are to be
+ * reclaimed, regardless of the zone occupancies. This is a software suspend
+ * special.
+ *
+ * Returns the number of pages which were actually freed.
+ *
+ * There is special handling here for zones which are full of pinned pages.
+ * This can happen if the pages are all mlocked, or if they are all used by
+ * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
+ * What we do is to detect the case where all pages in the zone have been
+ * scanned twice and there has been zero successful reclaim. Mark the zone as
+ * dead and from now on, only perform a short scan. Basically we're polling
+ * the zone for when the problem goes away.
+ *
+ * kswapd scans the zones in the highmem->normal->dma direction. It skips
+ * zones which have free_pages > pages_high, but once a zone is found to have
+ * free_pages <= pages_high, we scan that zone and the lower zones regardless
+ * of the number of free pages in the lower zones. This interoperates with
+ * the page allocator fallback scheme to ensure that aging of pages is balanced
+ * across the zones.
+ */
+static int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order)
+{
+ int to_free = nr_pages;
+ int all_zones_ok;
+ int priority;
+ int i;
+ int total_scanned, total_reclaimed;
+ struct reclaim_state *reclaim_state = current->reclaim_state;
+ struct scan_control sc;
+
+loop_again:
+ total_scanned = 0;
+ total_reclaimed = 0;
+ sc.gfp_mask = GFP_KERNEL;
+ sc.may_writepage = 0;
+ sc.nr_mapped = read_page_state(nr_mapped);
+
+ inc_page_state(pageoutrun);
+
+ for (i = 0; i < pgdat->nr_zones; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ zone->temp_priority = DEF_PRIORITY;
+ }
+
+ for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+ int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
+ unsigned long lru_pages = 0;
+
+ all_zones_ok = 1;
+
+ if (nr_pages == 0) {
+ /*
+ * Scan in the highmem->dma direction for the highest
+ * zone which needs scanning
+ */
+ for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (zone->present_pages == 0)
+ continue;
+
+ if (zone->all_unreclaimable &&
+ priority != DEF_PRIORITY)
+ continue;
+
+ if (!zone_watermark_ok(zone, order,
+ zone->pages_high, 0, 0, 0)) {
+ end_zone = i;
+ goto scan;
+ }
+ }
+ goto out;
+ } else {
+ end_zone = pgdat->nr_zones - 1;
+ }
+scan:
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ lru_pages += zone->nr_active + zone->nr_inactive;
+ }
+
+ /*
+ * Now scan the zone in the dma->highmem direction, stopping
+ * at the last zone which needs scanning.
+ *
+ * We do this because the page allocator works in the opposite
+ * direction. This prevents the page allocator from allocating
+ * pages behind kswapd's direction of progress, which would
+ * cause too much scanning of the lower zones.
+ */
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (zone->present_pages == 0)
+ continue;
+
+ if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ continue;
+
+ if (nr_pages == 0) { /* Not software suspend */
+ if (!zone_watermark_ok(zone, order,
+ zone->pages_high, end_zone, 0, 0))
+ all_zones_ok = 0;
+ }
+ zone->temp_priority = priority;
+ if (zone->prev_priority > priority)
+ zone->prev_priority = priority;
+ sc.nr_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.priority = priority;
+ sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
+ shrink_zone(zone, &sc);
+ reclaim_state->reclaimed_slab = 0;
+ shrink_slab(sc.nr_scanned, GFP_KERNEL, lru_pages);
+ sc.nr_reclaimed += reclaim_state->reclaimed_slab;
+ total_reclaimed += sc.nr_reclaimed;
+ total_scanned += sc.nr_scanned;
+ if (zone->all_unreclaimable)
+ continue;
+ if (zone->pages_scanned >= (zone->nr_active +
+ zone->nr_inactive) * 4)
+ zone->all_unreclaimable = 1;
+ /*
+ * If we've done a decent amount of scanning and
+ * the reclaim ratio is low, start doing writepage
+ * even in laptop mode
+ */
+ if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
+ total_scanned > total_reclaimed+total_reclaimed/2)
+ sc.may_writepage = 1;
+ }
+ if (nr_pages && to_free > total_reclaimed)
+ continue; /* swsusp: need to do more work */
+ if (all_zones_ok)
+ break; /* kswapd: all done */
+ /*
+ * OK, kswapd is getting into trouble. Take a nap, then take
+ * another pass across the zones.
+ */
+ if (total_scanned && priority < DEF_PRIORITY - 2)
+ blk_congestion_wait(WRITE, HZ/10);
+
+ /*
+ * We do this so kswapd doesn't build up large priorities for
+ * example when it is freeing in parallel with allocators. It
+ * matches the direct reclaim path behaviour in terms of impact
+ * on zone->*_priority.
+ */
+ if ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages))
+ break;
+ }
+out:
+ for (i = 0; i < pgdat->nr_zones; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ zone->prev_priority = zone->temp_priority;
+ }
+ if (!all_zones_ok) {
+ cond_resched();
+ goto loop_again;
+ }
+
+ return total_reclaimed;
+}
+
+/*
+ * The background pageout daemon, started as a kernel thread
+ * from the init process.
+ *
+ * This basically trickles out pages so that we have _some_
+ * free memory available even if there is no other activity
+ * that frees anything up. This is needed for things like routing
+ * etc, where we otherwise might have all activity going on in
+ * asynchronous contexts that cannot page things out.
+ *
+ * If there are applications that are active memory-allocators
+ * (most normal use), this basically shouldn't matter.
+ */
+static int kswapd(void *p)
+{
+ unsigned long order;
+ pg_data_t *pgdat = (pg_data_t*)p;
+ struct task_struct *tsk = current;
+ DEFINE_WAIT(wait);
+ struct reclaim_state reclaim_state = {
+ .reclaimed_slab = 0,
+ };
+ cpumask_t cpumask;
+
+ daemonize("kswapd%d", pgdat->node_id);
+ cpumask = node_to_cpumask(pgdat->node_id);
+ if (!cpus_empty(cpumask))
+ set_cpus_allowed(tsk, cpumask);
+ current->reclaim_state = &reclaim_state;
+
+ /*
+ * Tell the memory management that we're a "memory allocator",
+ * and that if we need more memory we should get access to it
+ * regardless (see "__alloc_pages()"). "kswapd" should
+ * never get caught in the normal page freeing logic.
+ *
+ * (Kswapd normally doesn't need memory anyway, but sometimes
+ * you need a small amount of memory in order to be able to
+ * page out something else, and this flag essentially protects
+ * us from recursively trying to free more memory as we're
+ * trying to free the first piece of memory in the first place).
+ */
+ tsk->flags |= PF_MEMALLOC|PF_KSWAPD;
+
+ order = 0;
+ for ( ; ; ) {
+ unsigned long new_order;
+ if (current->flags & PF_FREEZE)
+ refrigerator(PF_FREEZE);
+
+ prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+ new_order = pgdat->kswapd_max_order;
+ pgdat->kswapd_max_order = 0;
+ if (order < new_order) {
+ /*
+ * Don't sleep if someone wants a larger 'order'
+ * allocation
+ */
+ order = new_order;
+ } else {
+ schedule();
+ order = pgdat->kswapd_max_order;
+ }
+ finish_wait(&pgdat->kswapd_wait, &wait);
+
+ balance_pgdat(pgdat, 0, order);
+ }
+ return 0;
+}
+
+/*
+ * A zone is low on free memory, so wake its kswapd task to service it.
+ */
+void wakeup_kswapd(struct zone *zone, int order)
+{
+ pg_data_t *pgdat;
+
+ if (zone->present_pages == 0)
+ return;
+
+ pgdat = zone->zone_pgdat;
+ if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0, 0))
+ return;
+ if (pgdat->kswapd_max_order < order)
+ pgdat->kswapd_max_order = order;
+ if (!cpuset_zone_allowed(zone))
+ return;
+ if (!waitqueue_active(&zone->zone_pgdat->kswapd_wait))
+ return;
+ wake_up_interruptible(&zone->zone_pgdat->kswapd_wait);
+}
+
+#ifdef CONFIG_PM
+/*
+ * Try to free `nr_pages' of memory, system-wide. Returns the number of freed
+ * pages.
+ */
+int shrink_all_memory(int nr_pages)
+{
+ pg_data_t *pgdat;
+ int nr_to_free = nr_pages;
+ int ret = 0;
+ struct reclaim_state reclaim_state = {
+ .reclaimed_slab = 0,
+ };
+
+ current->reclaim_state = &reclaim_state;
+ for_each_pgdat(pgdat) {
+ int freed;
+ freed = balance_pgdat(pgdat, nr_to_free, 0);
+ ret += freed;
+ nr_to_free -= freed;
+ if (nr_to_free <= 0)
+ break;
+ }
+ current->reclaim_state = NULL;
+ return ret;
+}
+#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+/* It's optimal to keep kswapds on the same CPUs as their memory, but
+ not required for correctness. So if the last cpu in a node goes
+ away, we get changed to run anywhere: as the first one comes back,
+ restore their cpu bindings. */
+static int __devinit cpu_callback(struct notifier_block *nfb,
+ unsigned long action,
+ void *hcpu)
+{
+ pg_data_t *pgdat;
+ cpumask_t mask;
+
+ if (action == CPU_ONLINE) {
+ for_each_pgdat(pgdat) {
+ mask = node_to_cpumask(pgdat->node_id);
+ if (any_online_cpu(mask) != NR_CPUS)
+ /* One of our CPUs online: restore mask */
+ set_cpus_allowed(pgdat->kswapd, mask);
+ }
+ }
+ return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static int __init kswapd_init(void)
+{
+ pg_data_t *pgdat;
+ swap_setup();
+ for_each_pgdat(pgdat)
+ pgdat->kswapd
+ = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL));
+ total_memory = nr_free_pagecache_pages();
+ hotcpu_notifier(cpu_callback, 0);
+ return 0;
+}
+
+module_init(kswapd_init)