From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163669AbeCBABI (ORCPT ); Thu, 1 Mar 2018 19:01:08 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:42430 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1163565AbeCBABH (ORCPT ); Thu, 1 Mar 2018 19:01:07 -0500 Date: Thu, 1 Mar 2018 16:01:05 -0800 From: Andrew Morton To: Aaron Lu 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: <20180301160105.aca958fac871998d582307d4@linux-foundation.org> In-Reply-To: <20180301062845.26038-3-aaron.lu@intel.com> References: <20180301062845.26038-1-aaron.lu@intel.com> <20180301062845.26038-3-aaron.lu@intel.com> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 874DA6B0003 for ; Thu, 1 Mar 2018 19:01:09 -0500 (EST) Received: by mail-wr0-f197.google.com with SMTP id 96so2844941wrk.12 for ; Thu, 01 Mar 2018 16:01:09 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id q37si3646753wrb.536.2018.03.01.16.01.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Mar 2018 16:01:08 -0800 (PST) Date: Thu, 1 Mar 2018 16:01:05 -0800 From: Andrew Morton Subject: Re: [PATCH v4 2/3] mm/free_pcppages_bulk: do not hold lock when picking pages to free Message-Id: <20180301160105.aca958fac871998d582307d4@linux-foundation.org> In-Reply-To: <20180301062845.26038-3-aaron.lu@intel.com> References: <20180301062845.26038-1-aaron.lu@intel.com> <20180301062845.26038-3-aaron.lu@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Aaron Lu 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, 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. -- 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