From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753218AbeBZNxB (ORCPT ); Mon, 26 Feb 2018 08:53:01 -0500 Received: from mga04.intel.com ([192.55.52.120]:54609 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753086AbeBZNww (ORCPT ); Mon, 26 Feb 2018 08:52:52 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,396,1515484800"; d="scan'208";a="29836368" From: Aaron Lu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Huang Ying , Dave Hansen , Kemi Wang , Tim Chen , Andi Kleen , Michal Hocko , Vlastimil Babka , Mel Gorman , Matthew Wilcox Subject: [PATCH v3 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Date: Mon, 26 Feb 2018 21:53:45 +0800 Message-Id: <20180226135346.7208-3-aaron.lu@intel.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180226135346.7208-1-aaron.lu@intel.com> References: <20180226135346.7208-1-aaron.lu@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) v4.16-rc2+ 9034215 7971818 13667135 15677465 this patch 9536374 +5.6% 8314710 +4.3% 14070408 +3.0% 16675866 +6.4% What the test does is: starts $nr_cpu processes and each will repeatedly 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 Acked-by: Mel Gorman Signed-off-by: Aaron Lu --- mm/page_alloc.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3154859cccd6..35576da0a6c9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1116,13 +1116,11 @@ static void free_pcppages_bulk(struct zone *zone, int count, int migratetype = 0; int batch_free = 0; bool isolated_pageblocks; + struct page *page, *tmp; + LIST_HEAD(head); pcp->count -= count; - spin_lock(&zone->lock); - isolated_pageblocks = has_isolate_pageblock(zone); - while (count) { - struct page *page; struct list_head *list; /* @@ -1144,26 +1142,31 @@ 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