From: Aaron Lu <aaron.lu@intel.com> To: Michal Hocko <mhocko@kernel.org> 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: Fri, 2 Mar 2018 15:15:34 +0800 [thread overview] Message-ID: <20180302071533.GA6356@intel.com> (raw) In-Reply-To: <20180301135518.GJ15057@dhcp22.suse.cz> On Thu, Mar 01, 2018 at 02:55:18PM +0100, Michal Hocko wrote: > 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. Correct. > I am still quite surprised that this would have such a large impact. Most likely due to the cachelines for these page structures are warmed up outside of zone->lock.
WARNING: multiple messages have this Message-ID (diff)
From: Aaron Lu <aaron.lu@intel.com> To: Michal Hocko <mhocko@kernel.org> 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: Fri, 2 Mar 2018 15:15:34 +0800 [thread overview] Message-ID: <20180302071533.GA6356@intel.com> (raw) In-Reply-To: <20180301135518.GJ15057@dhcp22.suse.cz> On Thu, Mar 01, 2018 at 02:55:18PM +0100, Michal Hocko wrote: > 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. Correct. > I am still quite surprised that this would have such a large impact. Most likely due to the cachelines for these page structures are warmed up outside of zone->lock. -- 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:[~2018-03-02 7:14 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 2018-03-01 13:55 ` Michal Hocko 2018-03-02 7:15 ` Aaron Lu [this message] 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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