When freeing a batch of pages from Per-CPU-Pages(PCP) back to buddy, the zone->lock is held and then pages are chosen from PCP's migratetype list. While there is actually no need to do this 'choose part' under lock since it's PCP pages, the only CPU that can touch them is us and irq is also disabled. Moving this part outside could reduce lock held time and improve performance. Test with will-it-scale/page_fault1 full load: kernel Broadwell(2S) Skylake(2S) Broadwell(4S) Skylake(4S) v4.15-rc4 9037332 8000124 13642741 15728686 this patch 9608786 +6.3% 8368915 +4.6% 14042169 +2.9% 17433559 +10.8% What the test does is: starts $nr_cpu processes and each will repeated do the following for 5 minutes: 1 mmap 128M anonymouse space; 2 write access to that space; 3 munmap. The score is the aggregated iteration. https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault1.c Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> --- mm/page_alloc.c | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4093728f292e..a076f754dac1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1113,12 +1113,12 @@ static void free_pcppages_bulk(struct zone *zone, int count, int migratetype = 0; int batch_free = 0; bool isolated_pageblocks; + struct list_head head; + struct page *page, *tmp; - spin_lock(&zone->lock); - isolated_pageblocks = has_isolate_pageblock(zone); + INIT_LIST_HEAD(&head); while (count) { - struct page *page; struct list_head *list; /* @@ -1140,26 +1140,31 @@ static void free_pcppages_bulk(struct zone *zone, int count, batch_free = count; do { - int mt; /* migratetype of the to-be-freed page */ - page = list_last_entry(list, struct page, lru); /* must delete as __free_one_page list manipulates */ list_del(&page->lru); - mt = get_pcppage_migratetype(page); - /* MIGRATE_ISOLATE page should not go to pcplists */ - VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); - /* Pageblock could have been isolated meanwhile */ - if (unlikely(isolated_pageblocks)) - mt = get_pageblock_migratetype(page); - if (bulkfree_pcp_prepare(page)) continue; - __free_one_page(page, page_to_pfn(page), zone, 0, mt); - trace_mm_page_pcpu_drain(page, 0, mt); + list_add_tail(&page->lru, &head); } while (--count && --batch_free && !list_empty(list)); } + + spin_lock(&zone->lock); + isolated_pageblocks = has_isolate_pageblock(zone); + + list_for_each_entry_safe(page, tmp, &head, lru) { + int mt = get_pcppage_migratetype(page); + /* MIGRATE_ISOLATE page should not go to pcplists */ + VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); + /* Pageblock could have been isolated meanwhile */ + if (unlikely(isolated_pageblocks)) + mt = get_pageblock_migratetype(page); + + __free_one_page(page, page_to_pfn(page), zone, 0, mt); + trace_mm_page_pcpu_drain(page, 0, mt); + } spin_unlock(&zone->lock); } -- 2.14.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
