From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1034316AbeCBIAa (ORCPT ); Fri, 2 Mar 2018 03:00:30 -0500 Received: from mga04.intel.com ([192.55.52.120]:24578 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030476AbeCBIA2 (ORCPT ); Fri, 2 Mar 2018 03:00:28 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,411,1515484800"; d="scan'208";a="21512780" Date: Fri, 2 Mar 2018 16:01:25 +0800 From: Aaron Lu To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Dave Hansen , Kemi Wang , Tim Chen , Andi Kleen , Michal Hocko , Vlastimil Babka , Mel Gorman , Matthew Wilcox , David Rientjes Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Message-ID: <20180302080125.GB6356@intel.com> References: <20180301062845.26038-1-aaron.lu@intel.com> <20180301062845.26038-3-aaron.lu@intel.com> <20180301160105.aca958fac871998d582307d4@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180301160105.aca958fac871998d582307d4@linux-foundation.org> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 01, 2018 at 04:01:05PM -0800, Andrew Morton wrote: > On Thu, 1 Mar 2018 14:28:44 +0800 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. > > But it's a loss for uniprocessor systems: it adds more code and adds an > additional pass across a list. Performance wise, I assume the loss is pretty small and can not be measured. On my Sandybridge desktop, with will-it-scale/page_fault1/single process run to emulate uniprocessor system, the score is(average of 3 runs): base(patch 1/3): 649710 this patch: 653554 +0.6% prefetch(patch 3/3): 650336 (in noise range compared to base) On 4 sockets Intel Broadwell with will-it-scale/page_fault1/single process run: base(patch 1/3): 498649 this patch: 504171 +1.1% prefetch(patch 3/3): 506334 +1.5% (compared to base) It looks like we don't need to worry too much about performance for uniprocessor system. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id A673E6B0003 for ; Fri, 2 Mar 2018 03:00:26 -0500 (EST) Received: by mail-pf0-f199.google.com with SMTP id z5so4901424pfe.16 for ; Fri, 02 Mar 2018 00:00:26 -0800 (PST) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTPS id p2si3689885pga.143.2018.03.02.00.00.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Mar 2018 00:00:25 -0800 (PST) Date: Fri, 2 Mar 2018 16:01:25 +0800 From: Aaron Lu Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Message-ID: <20180302080125.GB6356@intel.com> References: <20180301062845.26038-1-aaron.lu@intel.com> <20180301062845.26038-3-aaron.lu@intel.com> <20180301160105.aca958fac871998d582307d4@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180301160105.aca958fac871998d582307d4@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Dave Hansen , Kemi Wang , Tim Chen , Andi Kleen , Michal Hocko , Vlastimil Babka , Mel Gorman , Matthew Wilcox , David Rientjes On Thu, Mar 01, 2018 at 04:01:05PM -0800, Andrew Morton wrote: > On Thu, 1 Mar 2018 14:28:44 +0800 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. > > But it's a loss for uniprocessor systems: it adds more code and adds an > additional pass across a list. Performance wise, I assume the loss is pretty small and can not be measured. On my Sandybridge desktop, with will-it-scale/page_fault1/single process run to emulate uniprocessor system, the score is(average of 3 runs): base(patch 1/3): 649710 this patch: 653554 +0.6% prefetch(patch 3/3): 650336 (in noise range compared to base) On 4 sockets Intel Broadwell with will-it-scale/page_fault1/single process run: base(patch 1/3): 498649 this patch: 504171 +1.1% prefetch(patch 3/3): 506334 +1.5% (compared to base) It looks like we don't need to worry too much about performance for uniprocessor system. -- 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: email@kvack.org