From: Michal Hocko <mhocko@kernel.org> To: Aaron Lu <aaron.lu@intel.com> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, Huang Ying <ying.huang@intel.com>, Dave Hansen <dave.hansen@intel.com>, Kemi Wang <kemi.wang@intel.com>, Tim Chen <tim.c.chen@linux.intel.com>, Andi Kleen <ak@linux.intel.com>, Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@techsingularity.net>, Matthew Wilcox <willy@infradead.org>, David Rientjes <rientjes@google.com> Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Date: Thu, 1 Mar 2018 14:55:18 +0100 [thread overview] Message-ID: <20180301135518.GJ15057@dhcp22.suse.cz> (raw) In-Reply-To: <20180301062845.26038-3-aaron.lu@intel.com> On Thu 01-03-18 14:28:44, Aaron Lu wrote: > 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. Iteration count I assume. I am still quite surprised that this would have such a large impact. > https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault1.c > > Acked-by: Mel Gorman <mgorman@techsingularity.net> > Signed-off-by: Aaron Lu <aaron.lu@intel.com> The patch makes sense to me Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/page_alloc.c | 39 +++++++++++++++++++++++---------------- > 1 file changed, 23 insertions(+), 16 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index faa33eac1635..dafdcdec9c1f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1116,12 +1116,10 @@ static void free_pcppages_bulk(struct zone *zone, int count, > int migratetype = 0; > int batch_free = 0; > bool isolated_pageblocks; > - > - spin_lock(&zone->lock); > - isolated_pageblocks = has_isolate_pageblock(zone); > + struct page *page, *tmp; > + LIST_HEAD(head); > > while (count) { > - struct page *page; > struct list_head *list; > > /* > @@ -1143,27 +1141,36 @@ 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 */ > + /* must delete to avoid corrupting pcp list */ > list_del(&page->lru); > pcp->count--; > > - 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); > + > + /* > + * Use safe version since after __free_one_page(), > + * page->lru.next will not point to original list. > + */ > + 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 > -- Michal Hocko SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: Aaron Lu <aaron.lu@intel.com> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, Huang Ying <ying.huang@intel.com>, Dave Hansen <dave.hansen@intel.com>, Kemi Wang <kemi.wang@intel.com>, Tim Chen <tim.c.chen@linux.intel.com>, Andi Kleen <ak@linux.intel.com>, Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@techsingularity.net>, Matthew Wilcox <willy@infradead.org>, David Rientjes <rientjes@google.com> Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Date: Thu, 1 Mar 2018 14:55:18 +0100 [thread overview] Message-ID: <20180301135518.GJ15057@dhcp22.suse.cz> (raw) In-Reply-To: <20180301062845.26038-3-aaron.lu@intel.com> On Thu 01-03-18 14:28:44, Aaron Lu wrote: > 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. Iteration count I assume. I am still quite surprised that this would have such a large impact. > https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault1.c > > Acked-by: Mel Gorman <mgorman@techsingularity.net> > Signed-off-by: Aaron Lu <aaron.lu@intel.com> The patch makes sense to me Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/page_alloc.c | 39 +++++++++++++++++++++++---------------- > 1 file changed, 23 insertions(+), 16 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index faa33eac1635..dafdcdec9c1f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1116,12 +1116,10 @@ static void free_pcppages_bulk(struct zone *zone, int count, > int migratetype = 0; > int batch_free = 0; > bool isolated_pageblocks; > - > - spin_lock(&zone->lock); > - isolated_pageblocks = has_isolate_pageblock(zone); > + struct page *page, *tmp; > + LIST_HEAD(head); > > while (count) { > - struct page *page; > struct list_head *list; > > /* > @@ -1143,27 +1141,36 @@ 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 */ > + /* must delete to avoid corrupting pcp list */ > list_del(&page->lru); > pcp->count--; > > - 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); > + > + /* > + * Use safe version since after __free_one_page(), > + * page->lru.next will not point to original list. > + */ > + 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 > -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2018-03-01 13:55 UTC|newest] Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-01 6:28 [PATCH v4 0/3] mm: improve zone->lock scalability Aaron Lu 2018-03-01 6:28 ` Aaron Lu 2018-03-01 6:28 ` [PATCH v4 1/3] mm/free_pcppages_bulk: update pcp->count inside Aaron Lu 2018-03-01 6:28 ` Aaron Lu 2018-03-01 12:11 ` David Rientjes 2018-03-01 12:11 ` David Rientjes 2018-03-01 13:45 ` Michal Hocko 2018-03-01 13:45 ` Michal Hocko 2018-03-12 13:22 ` Vlastimil Babka 2018-03-13 2:11 ` Aaron Lu 2018-03-01 6:28 ` [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Aaron Lu 2018-03-01 6:28 ` Aaron Lu 2018-03-01 13:55 ` Michal Hocko [this message] 2018-03-01 13:55 ` Michal Hocko 2018-03-02 7:15 ` Aaron Lu 2018-03-02 7:15 ` Aaron Lu 2018-03-02 15:34 ` Dave Hansen 2018-03-02 15:34 ` Dave Hansen 2018-03-02 7:31 ` Huang, Ying 2018-03-02 7:31 ` Huang, Ying 2018-03-02 0:01 ` Andrew Morton 2018-03-02 0:01 ` Andrew Morton 2018-03-02 8:01 ` Aaron Lu 2018-03-02 8:01 ` Aaron Lu 2018-03-02 21:23 ` Andrew Morton 2018-03-02 21:23 ` Andrew Morton 2018-03-02 21:25 ` Dave Hansen 2018-03-02 21:25 ` Dave Hansen 2018-03-12 14:22 ` Vlastimil Babka 2018-03-13 3:34 ` Aaron Lu 2018-03-22 15:17 ` Matthew Wilcox 2018-03-26 3:03 ` Aaron Lu 2018-03-01 6:28 ` [PATCH v4 3/3] mm/free_pcppages_bulk: prefetch buddy while not holding lock Aaron Lu 2018-03-01 6:28 ` Aaron Lu 2018-03-01 14:00 ` Michal Hocko 2018-03-01 14:00 ` Michal Hocko 2018-03-02 8:31 ` Aaron Lu 2018-03-02 8:31 ` Aaron Lu 2018-03-02 17:55 ` Vlastimil Babka 2018-03-02 17:55 ` Vlastimil Babka 2018-03-02 18:00 ` Dave Hansen 2018-03-02 18:00 ` Dave Hansen 2018-03-02 18:08 ` Vlastimil Babka 2018-03-02 18:08 ` Vlastimil Babka 2018-03-05 11:41 ` Aaron Lu 2018-03-05 11:41 ` Aaron Lu 2018-03-05 11:48 ` Aaron Lu 2018-03-05 11:48 ` Aaron Lu 2018-03-06 7:55 ` Vlastimil Babka 2018-03-06 7:55 ` Vlastimil Babka 2018-03-06 12:27 ` Aaron Lu 2018-03-06 12:27 ` Aaron Lu 2018-03-06 12:53 ` Matthew Wilcox 2018-03-06 12:53 ` Matthew Wilcox 2018-03-02 0:09 ` Andrew Morton 2018-03-02 0:09 ` Andrew Morton 2018-03-02 8:27 ` Aaron Lu 2018-03-02 8:27 ` Aaron Lu 2018-03-09 8:24 ` [PATCH v4 3/3 update] " Aaron Lu 2018-03-09 21:58 ` Andrew Morton 2018-03-10 14:46 ` Aaron Lu 2018-03-12 15:05 ` Vlastimil Babka 2018-03-12 17:32 ` Dave Hansen 2018-03-13 3:35 ` Aaron Lu 2018-03-13 7:04 ` Aaron Lu 2018-03-20 9:50 ` Vlastimil Babka 2018-03-20 11:31 ` [PATCH v4 3/3 update2] " Aaron Lu
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