1 files changed, 393 insertions, 0 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
new file mode 100644
index 000000000000..be1ff3f7552b
--- /dev/null
+++ b/mm/compaction.c
@@ -0,0 +1,393 @@
+/*
+ * linux/mm/compaction.c
+ *
+ * Memory compaction for the reduction of external fragmentation. Note that
+ * this heavily depends upon page migration to do all the real heavy
+ * lifting
+ *
+ * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
+ */
+#include <linux/swap.h>
+#include <linux/migrate.h>
+#include <linux/compaction.h>
+#include <linux/mm_inline.h>
+#include <linux/backing-dev.h>
+#include "internal.h"
+
+/*
+ * compact_control is used to track pages being migrated and the free pages
+ * they are being migrated to during memory compaction. The free_pfn starts
+ * at the end of a zone and migrate_pfn begins at the start. Movable pages
+ * are moved to the end of a zone during a compaction run and the run
+ * completes when free_pfn <= migrate_pfn
+ */
+struct compact_control {
+        struct list_head freepages;     /* List of free pages to migrate to */
+        struct list_head migratepages;  /* List of pages being migrated */
+        unsigned long nr_freepages;     /* Number of isolated free pages */
+        unsigned long nr_migratepages;  /* Number of pages to migrate */
+        unsigned long free_pfn;         /* isolate_freepages search base */
+        unsigned long migrate_pfn;      /* isolate_migratepages search base */
+
+        /* Account for isolated anon and file pages */
+        unsigned long nr_anon;
+        unsigned long nr_file;
+
+        struct zone *zone;
+};
+
+static unsigned long release_freepages(struct list_head *freelist)
+{
+        struct page *page, *next;
+        unsigned long count = 0;
+
+        list_for_each_entry_safe(page, next, freelist, lru) {
+                list_del(&page->lru);
+                __free_page(page);
+                count++;
+        }
+
+        return count;
+}
+
+/* Isolate free pages onto a private freelist. Must hold zone->lock */
+static unsigned long isolate_freepages_block(struct zone *zone,
+                                unsigned long blockpfn,
+                                struct list_head *freelist)
+{
+        unsigned long zone_end_pfn, end_pfn;
+        int total_isolated = 0;
+        struct page *cursor;
+
+        /* Get the last PFN we should scan for free pages at */
+        zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
+        end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);
+
+        /* Find the first usable PFN in the block to initialse page cursor */
+        for (; blockpfn < end_pfn; blockpfn++) {
+                if (pfn_valid_within(blockpfn))
+                        break;
+        }
+        cursor = pfn_to_page(blockpfn);
+
+        /* Isolate free pages. This assumes the block is valid */
+        for (; blockpfn < end_pfn; blockpfn++, cursor++) {
+                int isolated, i;
+                struct page *page = cursor;
+
+                if (!pfn_valid_within(blockpfn))
+                        continue;
+
+                if (!PageBuddy(page))
+                        continue;
+
+                /* Found a free page, break it into order-0 pages */
+                isolated = split_free_page(page);
+                total_isolated += isolated;
+                for (i = 0; i < isolated; i++) {
+                        list_add(&page->lru, freelist);
+                        page++;
+                }
+
+                /* If a page was split, advance to the end of it */
+                if (isolated) {
+                        blockpfn += isolated - 1;
+                        cursor += isolated - 1;
+                }
+        }
+
+        return total_isolated;
+}
+
+/* Returns true if the page is within a block suitable for migration to */
+static bool suitable_migration_target(struct page *page)
+{
+
+        int migratetype = get_pageblock_migratetype(page);
+
+        /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
+        if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
+                return false;
+
+        /* If the page is a large free page, then allow migration */
+        if (PageBuddy(page) && page_order(page) >= pageblock_order)
+                return true;
+
+        /* If the block is MIGRATE_MOVABLE, allow migration */
+        if (migratetype == MIGRATE_MOVABLE)
+                return true;
+
+        /* Otherwise skip the block */
+        return false;
+}
+
+/*
+ * Based on information in the current compact_control, find blocks
+ * suitable for isolating free pages from and then isolate them.
+ */
+static void isolate_freepages(struct zone *zone,
+                                struct compact_control *cc)
+{
+        struct page *page;
+        unsigned long high_pfn, low_pfn, pfn;
+        unsigned long flags;
+        int nr_freepages = cc->nr_freepages;
+        struct list_head *freelist = &cc->freepages;
+
+        pfn = cc->free_pfn;
+        low_pfn = cc->migrate_pfn + pageblock_nr_pages;
+        high_pfn = low_pfn;
+
+        /*
+         * Isolate free pages until enough are available to migrate the
+         * pages on cc->migratepages. We stop searching if the migrate
+         * and free page scanners meet or enough free pages are isolated.
+         */
+        spin_lock_irqsave(&zone->lock, flags);
+        for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
+                                        pfn -= pageblock_nr_pages) {
+                unsigned long isolated;
+
+                if (!pfn_valid(pfn))
+                        continue;
+
+                /*
+                 * Check for overlapping nodes/zones. It's possible on some
+                 * configurations to have a setup like
+                 * node0 node1 node0
+                 * i.e. it's possible that all pages within a zones range of
+                 * pages do not belong to a single zone.
+                 */
+                page = pfn_to_page(pfn);
+                if (page_zone(page) != zone)
+                        continue;
+
+                /* Check the block is suitable for migration */
+                if (!suitable_migration_target(page))
+                        continue;
+
+                /* Found a block suitable for isolating free pages from */
+                isolated = isolate_freepages_block(zone, pfn, freelist);
+                nr_freepages += isolated;
+
+                /*
+                 * Record the highest PFN we isolated pages from. When next
+                 * looking for free pages, the search will restart here as
+                 * page migration may have returned some pages to the allocator
+                 */
+                if (isolated)
+                        high_pfn = max(high_pfn, pfn);
+        }
+        spin_unlock_irqrestore(&zone->lock, flags);
+
+        /* split_free_page does not map the pages */
+        list_for_each_entry(page, freelist, lru) {
+                arch_alloc_page(page, 0);
+                kernel_map_pages(page, 1, 1);
+        }
+
+        cc->free_pfn = high_pfn;
+        cc->nr_freepages = nr_freepages;
+}
+
+/* Update the number of anon and file isolated pages in the zone */
+static void acct_isolated(struct zone *zone, struct compact_control *cc)
+{
+        struct page *page;
+        unsigned int count[NR_LRU_LISTS] = { 0, };
+
+        list_for_each_entry(page, &cc->migratepages, lru) {
+                int lru = page_lru_base_type(page);
+                count[lru]++;
+        }
+
+        cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+        cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+        __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
+        __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
+}
+
+/* Similar to reclaim, but different enough that they don't share logic */
+static bool too_many_isolated(struct zone *zone)
+{
+
+        unsigned long inactive, isolated;
+
+        inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
+                                        zone_page_state(zone, NR_INACTIVE_ANON);
+        isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
+                                        zone_page_state(zone, NR_ISOLATED_ANON);
+
+        return isolated > inactive;
+}
+
+/*
+ * Isolate all pages that can be migrated from the block pointed to by
+ * the migrate scanner within compact_control.
+ */
+static unsigned long isolate_migratepages(struct zone *zone,
+                                        struct compact_control *cc)
+{
+        unsigned long low_pfn, end_pfn;
+        struct list_head *migratelist = &cc->migratepages;
+
+        /* Do not scan outside zone boundaries */
+        low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
+
+        /* Only scan within a pageblock boundary */
+        end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
+
+        /* Do not cross the free scanner or scan within a memory hole */
+        if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
+                cc->migrate_pfn = end_pfn;
+                return 0;
+        }
+
+        /*
+         * Ensure that there are not too many pages isolated from the LRU
+         * list by either parallel reclaimers or compaction. If there are,
+         * delay for some time until fewer pages are isolated
+         */
+        while (unlikely(too_many_isolated(zone))) {
+                congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+                if (fatal_signal_pending(current))
+                        return 0;
+        }
+
+        /* Time to isolate some pages for migration */
+        spin_lock_irq(&zone->lru_lock);
+        for (; low_pfn < end_pfn; low_pfn++) {
+                struct page *page;
+                if (!pfn_valid_within(low_pfn))
+                        continue;
+
+                /* Get the page and skip if free */
+                page = pfn_to_page(low_pfn);
+                if (PageBuddy(page))
+                        continue;
+
+                /* Try isolate the page */
+                if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
+                        continue;
+
+                /* Successfully isolated */
+                del_page_from_lru_list(zone, page, page_lru(page));
+                list_add(&page->lru, migratelist);
+                mem_cgroup_del_lru(page);
+                cc->nr_migratepages++;
+
+                /* Avoid isolating too much */
+                if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
+                        break;
+        }
+
+        acct_isolated(zone, cc);
+
+        spin_unlock_irq(&zone->lru_lock);
+        cc->migrate_pfn = low_pfn;
+
+        return cc->nr_migratepages;
+}
+
+/*
+ * This is a migrate-callback that "allocates" freepages by taking pages
+ * from the isolated freelists in the block we are migrating to.
+ */
+static struct page *compaction_alloc(struct page *migratepage,
+                                        unsigned long data,
+                                        int **result)
+{
+        struct compact_control *cc = (struct compact_control *)data;
+        struct page *freepage;
+
+        /* Isolate free pages if necessary */
+        if (list_empty(&cc->freepages)) {
+                isolate_freepages(cc->zone, cc);
+
+                if (list_empty(&cc->freepages))
+                        return NULL;
+        }
+
+        freepage = list_entry(cc->freepages.next, struct page, lru);
+        list_del(&freepage->lru);
+        cc->nr_freepages--;
+
+        return freepage;
+}
+
+/*
+ * We cannot control nr_migratepages and nr_freepages fully when migration is
+ * running as migrate_pages() has no knowledge of compact_control. When
+ * migration is complete, we count the number of pages on the lists by hand.
+ */
+static void update_nr_listpages(struct compact_control *cc)
+{
+        int nr_migratepages = 0;
+        int nr_freepages = 0;
+        struct page *page;
+
+        list_for_each_entry(page, &cc->migratepages, lru)
+                nr_migratepages++;
+        list_for_each_entry(page, &cc->freepages, lru)
+                nr_freepages++;
+
+        cc->nr_migratepages = nr_migratepages;
+        cc->nr_freepages = nr_freepages;
+}
+
+static int compact_finished(struct zone *zone,
+                                                struct compact_control *cc)
+{
+        if (fatal_signal_pending(current))
+                return COMPACT_PARTIAL;
+
+        /* Compaction run completes if the migrate and free scanner meet */
+        if (cc->free_pfn <= cc->migrate_pfn)
+                return COMPACT_COMPLETE;
+
+        return COMPACT_CONTINUE;
+}
+
+static int compact_zone(struct zone *zone, struct compact_control *cc)
+{
+        int ret;
+
+        /* Setup to move all movable pages to the end of the zone */
+        cc->migrate_pfn = zone->zone_start_pfn;
+        cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
+        cc->free_pfn &= ~(pageblock_nr_pages-1);
+
+        migrate_prep_local();
+
+        while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
+                unsigned long nr_migrate, nr_remaining;
+
+                if (!isolate_migratepages(zone, cc))
+                        continue;
+
+                nr_migrate = cc->nr_migratepages;
+                migrate_pages(&cc->migratepages, compaction_alloc,
+                                                (unsigned long)cc, 0);
+                update_nr_listpages(cc);
+                nr_remaining = cc->nr_migratepages;
+
+                count_vm_event(COMPACTBLOCKS);
+                count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
+                if (nr_remaining)
+                        count_vm_events(COMPACTPAGEFAILED, nr_remaining);
+
+                /* Release LRU pages not migrated */
+                if (!list_empty(&cc->migratepages)) {
+                        putback_lru_pages(&cc->migratepages);
+                        cc->nr_migratepages = 0;
+                }
+
+        }
+
+        /* Release free pages and check accounting */
+        cc->nr_freepages -= release_freepages(&cc->freepages);
+        VM_BUG_ON(cc->nr_freepages != 0);
+
+        return ret;
+}