From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id B0F1D6B0003 for ; Fri, 2 Mar 2018 02:14:36 -0500 (EST) Received: by mail-pg0-f72.google.com with SMTP id k62so3758121pgd.11 for ; Thu, 01 Mar 2018 23:14:36 -0800 (PST) Received: from mga17.intel.com (mga17.intel.com. [192.55.52.151]) by mx.google.com with ESMTPS id 61-v6si4443032plf.640.2018.03.01.23.14.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Mar 2018 23:14:35 -0800 (PST) Date: Fri, 2 Mar 2018 15:15:34 +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: <20180302071533.GA6356@intel.com> References: <20180301062845.26038-1-aaron.lu@intel.com> <20180301062845.26038-3-aaron.lu@intel.com> <20180301135518.GJ15057@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180301135518.GJ15057@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Huang Ying , Dave Hansen , Kemi Wang , Tim Chen , Andi Kleen , Vlastimil Babka , Mel Gorman , Matthew Wilcox , David Rientjes 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: email@kvack.org