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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 672F4C352BE for ; Fri, 17 Apr 2020 12:22:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43F7520656 for ; Fri, 17 Apr 2020 12:22:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="rN7z2enz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728992AbgDQMWF (ORCPT ); Fri, 17 Apr 2020 08:22:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727877AbgDQMWE (ORCPT ); Fri, 17 Apr 2020 08:22:04 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B05B2C061A0C for ; Fri, 17 Apr 2020 05:22:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=SLoUm+BzJe/VKqHJ2ONW40lm1UdZG6XkpJnj2k6pZhc=; b=rN7z2enzlzxrutdF0NtmuQYPMY FkSfXw/WcKyzu0QT0EMWZTbjBbJZcT37xLdgwwBW3cTGQvr1MjV7ivrplxL0DTFefuvf7jCB5aKI4 Rss3b3QP3pu0n6cmPEvRXIzW9lb2cQrJC3XRfT4E6KnCj3Ndd/axunrxs1TNfxk8wXC+SmlZcV9WO ju7AiL6ppeFYp6fyjhYR2IvaayU0pV4gnV3nJAQjKjfM7SVOR8hv+3PPV2ra6slIWRthniferaoqK QCFRDRT9z6CxEP0GMYaYAEyZxd7TPh78WiRB0TCd/NCuMVMo/fg90Q/zaLYdLqRw5QDyfhLxYgve+ 17TCG+MQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jPQ0E-0002iW-SY; Fri, 17 Apr 2020 12:21:51 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6F05B307005; Fri, 17 Apr 2020 14:21:48 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 208812B121525; Fri, 17 Apr 2020 14:21:48 +0200 (CEST) Date: Fri, 17 Apr 2020 14:21:48 +0200 From: Peter Zijlstra To: Mel Gorman Cc: SeongJae Park , "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: <20200417122148.GC20730@hirez.programming.kicks-ass.net> References: <20200417100417.GT20730@hirez.programming.kicks-ass.net> <20200417102129.23399-1-sjpark@amazon.com> <20200417121629.GA3758@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200417121629.GA3758@techsingularity.net> 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 01:16:29PM +0100, Mel Gorman wrote: > 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. Oh, quite agreed; I was just saying I never saw the use of that whole DAMON thing. AFAICT it's not actually solving a problem, just making more.