diff options
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 605 |
1 files changed, 605 insertions, 0 deletions
diff --git a/mm/compaction.c b/mm/compaction.c new file mode 100644 index 0000000..94cce51 --- /dev/null +++ b/mm/compaction.c @@ -0,0 +1,605 @@ +/* + * 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 <linux/sysctl.h> +#include <linux/sysfs.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; + + unsigned int order; /* order a direct compactor needs */ + int migratetype; /* MOVABLE, RECLAIMABLE etc */ + 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) +{ + unsigned int order; + unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order); + + 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; + + /* Compaction run is not finished if the watermark is not met */ + if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) + return COMPACT_CONTINUE; + + if (cc->order == -1) + return COMPACT_CONTINUE; + + /* Direct compactor: Is a suitable page free? */ + for (order = cc->order; order < MAX_ORDER; order++) { + /* Job done if page is free of the right migratetype */ + if (!list_empty(&zone->free_area[order].free_list[cc->migratetype])) + return COMPACT_PARTIAL; + + /* Job done if allocation would set block type */ + if (order >= pageblock_order && zone->free_area[order].nr_free) + return COMPACT_PARTIAL; + } + + 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; +} + +static unsigned long compact_zone_order(struct zone *zone, + int order, gfp_t gfp_mask) +{ + struct compact_control cc = { + .nr_freepages = 0, + .nr_migratepages = 0, + .order = order, + .migratetype = allocflags_to_migratetype(gfp_mask), + .zone = zone, + }; + INIT_LIST_HEAD(&cc.freepages); + INIT_LIST_HEAD(&cc.migratepages); + + return compact_zone(zone, &cc); +} + +int sysctl_extfrag_threshold = 500; + +/** + * try_to_compact_pages - Direct compact to satisfy a high-order allocation + * @zonelist: The zonelist used for the current allocation + * @order: The order of the current allocation + * @gfp_mask: The GFP mask of the current allocation + * @nodemask: The allowed nodes to allocate from + * + * This is the main entry point for direct page compaction. + */ +unsigned long try_to_compact_pages(struct zonelist *zonelist, + int order, gfp_t gfp_mask, nodemask_t *nodemask) +{ + enum zone_type high_zoneidx = gfp_zone(gfp_mask); + int may_enter_fs = gfp_mask & __GFP_FS; + int may_perform_io = gfp_mask & __GFP_IO; + unsigned long watermark; + struct zoneref *z; + struct zone *zone; + int rc = COMPACT_SKIPPED; + + /* + * Check whether it is worth even starting compaction. The order check is + * made because an assumption is made that the page allocator can satisfy + * the "cheaper" orders without taking special steps + */ + if (order <= PAGE_ALLOC_COSTLY_ORDER || !may_enter_fs || !may_perform_io) + return rc; + + count_vm_event(COMPACTSTALL); + + /* Compact each zone in the list */ + for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, + nodemask) { + int fragindex; + int status; + + /* + * Watermarks for order-0 must be met for compaction. Note + * the 2UL. This is because during migration, copies of + * pages need to be allocated and for a short time, the + * footprint is higher + */ + watermark = low_wmark_pages(zone) + (2UL << order); + if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) + continue; + + /* + * fragmentation index determines if allocation failures are + * due to low memory or external fragmentation + * + * index of -1 implies allocations might succeed depending + * on watermarks + * index towards 0 implies failure is due to lack of memory + * index towards 1000 implies failure is due to fragmentation + * + * Only compact if a failure would be due to fragmentation. + */ + fragindex = fragmentation_index(zone, order); + if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) + continue; + + if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) { + rc = COMPACT_PARTIAL; + break; + } + + status = compact_zone_order(zone, order, gfp_mask); + rc = max(status, rc); + + if (zone_watermark_ok(zone, order, watermark, 0, 0)) + break; + } + + return rc; +} + + +/* Compact all zones within a node */ +static int compact_node(int nid) +{ + int zoneid; + pg_data_t *pgdat; + struct zone *zone; + + if (nid < 0 || nid >= nr_node_ids || !node_online(nid)) + return -EINVAL; + pgdat = NODE_DATA(nid); + + /* Flush pending updates to the LRU lists */ + lru_add_drain_all(); + + for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { + struct compact_control cc = { + .nr_freepages = 0, + .nr_migratepages = 0, + .order = -1, + }; + + zone = &pgdat->node_zones[zoneid]; + if (!populated_zone(zone)) + continue; + + cc.zone = zone; + INIT_LIST_HEAD(&cc.freepages); + INIT_LIST_HEAD(&cc.migratepages); + + compact_zone(zone, &cc); + + VM_BUG_ON(!list_empty(&cc.freepages)); + VM_BUG_ON(!list_empty(&cc.migratepages)); + } + + return 0; +} + +/* Compact all nodes in the system */ +static int compact_nodes(void) +{ + int nid; + + for_each_online_node(nid) + compact_node(nid); + + return COMPACT_COMPLETE; +} + +/* The written value is actually unused, all memory is compacted */ +int sysctl_compact_memory; + +/* This is the entry point for compacting all nodes via /proc/sys/vm */ +int sysctl_compaction_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *length, loff_t *ppos) +{ + if (write) + return compact_nodes(); + + return 0; +} + +int sysctl_extfrag_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *length, loff_t *ppos) +{ + proc_dointvec_minmax(table, write, buffer, length, ppos); + + return 0; +} + +#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) +ssize_t sysfs_compact_node(struct sys_device *dev, + struct sysdev_attribute *attr, + const char *buf, size_t count) +{ + compact_node(dev->id); + + return count; +} +static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); + +int compaction_register_node(struct node *node) +{ + return sysdev_create_file(&node->sysdev, &attr_compact); +} + +void compaction_unregister_node(struct node *node) +{ + return sysdev_remove_file(&node->sysdev, &attr_compact); +} +#endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
