From 70647c4e712bcfa25dedbff2a689742ea537286d Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Fri, 28 Sep 2012 10:19:36 +1000 Subject: [PATCH] mm: cma: discard clean pages during contiguous allocation instead of migration Drop clean cache pages instead of migration during alloc_contig_range() to minimise allocation latency by reducing the amount of migration that is necessary. It's useful for CMA because latency of migration is more important than evicting the background process's working set. In addition, as pages are reclaimed then fewer free pages for migration targets are required so it avoids memory reclaiming to get free pages, which is a contributory factor to increased latency. I measured elapsed time of __alloc_contig_migrate_range() which migrates 10M in 40M movable zone in QEMU machine. Before - 146ms, After - 7ms Signed-off-by: Mel Gorman Signed-off-by: Minchan Kim Reviewed-by: Mel Gorman Cc: Marek Szyprowski Acked-by: Michal Nazarewicz Cc: Rik van Riel Tested-by: Kyungmin Park Signed-off-by: Andrew Morton --- mm/internal.h | 3 ++- mm/page_alloc.c | 2 ++ mm/vmscan.c | 43 +++++++++++++++++++++++++++++++++++++------ 3 files changed, 41 insertions(+), 7 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index bbd7b34db4ea..8312d4fadf59 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -356,5 +356,6 @@ extern unsigned long vm_mmap_pgoff(struct file *, unsigned long, unsigned long, unsigned long); extern void set_pageblock_order(void); - +unsigned long reclaim_clean_pages_from_list(struct zone *zone, + struct list_head *page_list); #endif /* __MM_INTERNAL_H */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a5c546c20058..028617d1ca65 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5699,6 +5699,8 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end) break; } + reclaim_clean_pages_from_list(cc.zone, &cc.migratepages); + ret = migrate_pages(&cc.migratepages, __alloc_contig_migrate_alloc, 0, false, MIGRATE_SYNC); diff --git a/mm/vmscan.c b/mm/vmscan.c index d16bf5a53266..f8f56f8bc9c7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -674,8 +674,10 @@ static enum page_references page_check_references(struct page *page, static unsigned long shrink_page_list(struct list_head *page_list, struct zone *zone, struct scan_control *sc, + enum ttu_flags ttu_flags, unsigned long *ret_nr_dirty, - unsigned long *ret_nr_writeback) + unsigned long *ret_nr_writeback, + bool force_reclaim) { LIST_HEAD(ret_pages); LIST_HEAD(free_pages); @@ -689,10 +691,10 @@ static unsigned long shrink_page_list(struct list_head *page_list, mem_cgroup_uncharge_start(); while (!list_empty(page_list)) { - enum page_references references; struct address_space *mapping; struct page *page; int may_enter_fs; + enum page_references references = PAGEREF_RECLAIM; cond_resched(); @@ -758,7 +760,9 @@ static unsigned long shrink_page_list(struct list_head *page_list, wait_on_page_writeback(page); } - references = page_check_references(page, sc); + if (!force_reclaim) + references = page_check_references(page, sc); + switch (references) { case PAGEREF_ACTIVATE: goto activate_locked; @@ -788,7 +792,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, * processes. Try to unmap it here. */ if (page_mapped(page) && mapping) { - switch (try_to_unmap(page, TTU_UNMAP)) { + switch (try_to_unmap(page, ttu_flags)) { case SWAP_FAIL: goto activate_locked; case SWAP_AGAIN: @@ -960,6 +964,33 @@ keep: return nr_reclaimed; } +unsigned long reclaim_clean_pages_from_list(struct zone *zone, + struct list_head *page_list) +{ + struct scan_control sc = { + .gfp_mask = GFP_KERNEL, + .priority = DEF_PRIORITY, + .may_unmap = 1, + }; + unsigned long ret, dummy1, dummy2; + struct page *page, *next; + LIST_HEAD(clean_pages); + + list_for_each_entry_safe(page, next, page_list, lru) { + if (page_is_file_cache(page) && !PageDirty(page)) { + ClearPageActive(page); + list_move(&page->lru, &clean_pages); + } + } + + ret = shrink_page_list(&clean_pages, zone, &sc, + TTU_UNMAP|TTU_IGNORE_ACCESS, + &dummy1, &dummy2, true); + list_splice(&clean_pages, page_list); + __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret); + return ret; +} + /* * Attempt to remove the specified page from its LRU. Only take this page * if it is of the appropriate PageActive status. Pages which are being @@ -1278,8 +1309,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, if (nr_taken == 0) return 0; - nr_reclaimed = shrink_page_list(&page_list, zone, sc, - &nr_dirty, &nr_writeback); + nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP, + &nr_dirty, &nr_writeback, false); spin_lock_irq(&zone->lru_lock); -- 2.39.5