From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6AB1C352BE for ; Fri, 17 Apr 2020 12:16:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBEA720644 for ; Fri, 17 Apr 2020 12:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728903AbgDQMQq (ORCPT ); Fri, 17 Apr 2020 08:16:46 -0400 Received: from outbound-smtp54.blacknight.com ([46.22.136.238]:51915 "EHLO outbound-smtp54.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728071AbgDQMQp (ORCPT ); Fri, 17 Apr 2020 08:16:45 -0400 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp54.blacknight.com (Postfix) with ESMTPS id 705E1FAB1D for ; Fri, 17 Apr 2020 13:16:43 +0100 (IST) Received: (qmail 20170 invoked from network); 17 Apr 2020 12:16:43 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.18.57]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 17 Apr 2020 12:16:43 -0000 Date: Fri, 17 Apr 2020 13:16:29 +0100 From: Mel Gorman To: SeongJae Park Cc: Peter Zijlstra , "Huang, Ying" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ingo Molnar , Mel Gorman , Rik van Riel , Daniel Jordan , Tejun Heo , Dave Hansen , Tim Chen , Aubrey Li Subject: Re: Re: Re: [RFC] autonuma: Support to scan page table asynchronously Message-ID: <20200417121629.GA3758@techsingularity.net> References: <20200417100417.GT20730@hirez.programming.kicks-ass.net> <20200417102129.23399-1-sjpark@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20200417102129.23399-1-sjpark@amazon.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 17, 2020 at 12:21:29PM +0200, SeongJae Park wrote: > On Fri, 17 Apr 2020 12:04:17 +0200 Peter Zijlstra wrote: > > > On Fri, Apr 17, 2020 at 09:05:08AM +0200, SeongJae Park wrote: > > > I think the main idea of DAMON[1] might be able to applied here. Have you > > > considered it? > > > > > > [1] https://lore.kernel.org/linux-mm/20200406130938.14066-1-sjpark@amazon.com/ > > > > I've ignored that entire thing after you said the information it > > provides was already available through the PMU. > > Sorry if my answer made you confused. What I wanted to say was that the > fundamental access checking mechanism that DAMON depends on is PTE Accessed bit > for now, but it could be modified to use PMU or other features instead. I would not be inclined to lean towards either approach for NUMA balancing. Fiddling with the accessed bit can have consequences for page aging and residency -- fine for debugging a problem, not to fine for normal usage. I would expect the PMU approach would have high overhead as well as taking over a PMU counter that userspace debugging may expect to be available. -- Mel Gorman SUSE Labs