| /* |
| * 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" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/compaction.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 */ |
| bool sync; /* Synchronous migration */ |
| |
| /* 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 nr_scanned = 0, 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; |
| nr_scanned++; |
| |
| 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; |
| } |
| } |
| |
| trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); |
| 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 active, inactive, isolated; |
| |
| inactive = zone_page_state(zone, NR_INACTIVE_FILE) + |
| zone_page_state(zone, NR_INACTIVE_ANON); |
| active = zone_page_state(zone, NR_ACTIVE_FILE) + |
| zone_page_state(zone, NR_ACTIVE_ANON); |
| isolated = zone_page_state(zone, NR_ISOLATED_FILE) + |
| zone_page_state(zone, NR_ISOLATED_ANON); |
| |
| return isolated > (inactive + active) / 2; |
| } |
| |
| /* |
| * 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; |
| unsigned long nr_scanned = 0, nr_isolated = 0; |
| 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; |
| nr_scanned++; |
| |
| /* 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); |
| cc->nr_migratepages++; |
| nr_isolated++; |
| |
| /* 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; |
| |
| trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); |
| |
| 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; |
| } |
| |
| /* |
| * compaction_suitable: Is this suitable to run compaction on this zone now? |
| * Returns |
| * COMPACT_SKIPPED - If there are too few free pages for compaction |
| * COMPACT_PARTIAL - If the allocation would succeed without compaction |
| * COMPACT_CONTINUE - If compaction should run now |
| */ |
| unsigned long compaction_suitable(struct zone *zone, int order) |
| { |
| int fragindex; |
| unsigned long watermark; |
| |
| /* |
| * 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)) |
| return COMPACT_SKIPPED; |
| |
| /* |
| * fragmentation index determines if allocation failures are due to |
| * low memory or external fragmentation |
| * |
| * index of -1 implies allocations might succeed dependingon 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) |
| return COMPACT_SKIPPED; |
| |
| if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) |
| return COMPACT_PARTIAL; |
| |
| return COMPACT_CONTINUE; |
| } |
| |
| static int compact_zone(struct zone *zone, struct compact_control *cc) |
| { |
| int ret; |
| |
| ret = compaction_suitable(zone, cc->order); |
| switch (ret) { |
| case COMPACT_PARTIAL: |
| case COMPACT_SKIPPED: |
| /* Compaction is likely to fail */ |
| return ret; |
| case COMPACT_CONTINUE: |
| /* Fall through to compaction */ |
| ; |
| } |
| |
| /* 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, |
| cc->sync); |
| 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); |
| trace_mm_compaction_migratepages(nr_migrate - nr_remaining, |
| 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; |
| } |
| |
| unsigned long compact_zone_order(struct zone *zone, |
| int order, gfp_t gfp_mask, |
| bool sync) |
| { |
| struct compact_control cc = { |
| .nr_freepages = 0, |
| .nr_migratepages = 0, |
| .order = order, |
| .migratetype = allocflags_to_migratetype(gfp_mask), |
| .zone = zone, |
| .sync = sync, |
| }; |
| 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 |
| * @sync: Whether migration is synchronous or not |
| * |
| * 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, |
| bool sync) |
| { |
| 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; |
| 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 status; |
| |
| status = compact_zone_order(zone, order, gfp_mask, sync); |
| rc = max(status, rc); |
| |
| /* If a normal allocation would succeed, stop compacting */ |
| if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 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 */ |