Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751246AbdHROq0 (ORCPT ); Fri, 18 Aug 2017 10:46:26 -0400 Received: from outbound-smtp09.blacknight.com ([46.22.139.14]:58711 "EHLO outbound-smtp09.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881AbdHROqZ (ORCPT ); Fri, 18 Aug 2017 10:46:25 -0400 Date: Fri, 18 Aug 2017 15:46:22 +0100 From: Mel Gorman To: "Liang, Kan" Cc: Linus Torvalds , Mel Gorman , "Kirill A. Shutemov" , Tim Chen , Peter Zijlstra , Ingo Molnar , Andi Kleen , Andrew Morton , Johannes Weiner , Jan Kara , linux-mm , Linux Kernel Mailing List Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk Message-ID: <20170818144622.oabozle26hasg5yo@techsingularity.net> References: <84c7f26182b7f4723c0fe3b34ba912a9de92b8b7.1502758114.git.tim.c.chen@linux.intel.com> <37D7C6CF3E00A74B8858931C1DB2F07753786CE9@SHSMSX103.ccr.corp.intel.com> <37D7C6CF3E00A74B8858931C1DB2F0775378761B@SHSMSX103.ccr.corp.intel.com> <20170818122339.24grcbzyhnzmr4qw@techsingularity.net> <37D7C6CF3E00A74B8858931C1DB2F077537879BB@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077537879BB@SHSMSX103.ccr.corp.intel.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1020 Lines: 25 On Fri, Aug 18, 2017 at 02:20:38PM +0000, Liang, Kan wrote: > > Nothing fancy other than needing a comment if it works. > > > > No, the patch doesn't work. > That indicates that it may be a hot page and it's possible that the page is locked for a short time but waiters accumulate. What happens if you leave NUMA balancing enabled but disable THP? Waiting on migration entries also uses wait_on_page_locked so it would be interesting to know if the problem is specific to THP. Can you tell me what this workload is doing? I want to see if it's something like many threads pounding on a limited number of pages very quickly. If it's many threads working on private data, it would also be important to know how each buffers threads are aligned, particularly if the buffers are smaller than a THP or base page size. For example, if each thread is operating on a base page sized buffer then disabling THP would side-step the problem but THP would be false sharing between multiple threads. -- Mel Gorman SUSE Labs