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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 51018C4360C for ; Tue, 8 Oct 2019 14:44:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AF3421721 for ; Tue, 8 Oct 2019 14:44:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="y65D0zMl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727219AbfJHOol (ORCPT ); Tue, 8 Oct 2019 10:44:41 -0400 Received: from mail-ed1-f67.google.com ([209.85.208.67]:34149 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726057AbfJHOok (ORCPT ); Tue, 8 Oct 2019 10:44:40 -0400 Received: by mail-ed1-f67.google.com with SMTP id p10so15891798edq.1 for ; Tue, 08 Oct 2019 07:44:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=roNGOd3FOBsYLcw6p6AfNsDfUlpEWk12K8lCSg6iAUY=; b=y65D0zMlciZ3pKMueE9P/nkUSG2s2/S9BTNNDHGb/WgvM/3pFToz8zmyClu6SIbzkk sEQmikJFrj2iHOL7IGwkeUWjamJVgSWk3cYBP1PNNjrr/agjKJX4rXyqIGi4zoLzeNan nAJ9XfaeBIpVqlv0WKrMV6KsA18TiyBIMjqJUJMWsk7M5IU3RUEfolfStiafA2TSRBlA ZWReAlrO9npe3o+Hhfam0Qb3FZraz2sWMiSj1WALXsJTnYobtVR63+n2+CEHj8NO/Mcp l6uBVJ8+IVjhHooVDzJ4PJK+wdJRTJQtw5y0OD42C09JBaH6Yitq5n/PBFV8zIUBjIkD FQvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=roNGOd3FOBsYLcw6p6AfNsDfUlpEWk12K8lCSg6iAUY=; b=ZDoFLxSZATbi1v2o4kBxksc3+NYYPg7sBJtuSeeDD2USBvJHNLSMko3NUXOuGs4LHm RogEywCmQuJeX2cMTzAWvZu7V831uYZWp6y8tQiNLMnej95CHUf5dxlloggyWe2l9pWM w5DZ47O+j8+F0T7+I3v06DfG/b03A1+LyS3l0UVDS0b8InJsm+btvcRD6+3EaBRo90+E LZEJZ3da/ylDYEqu2ZY69nrQm1lEGhfJBFagN90VPF+di6q7rPZ4KSdebkTbusfqDxTM Oyh8C19wsK4NlOR9NpAvrm1bEMg4/JaQqZDjPD95N8pN4xrZRJTQn3qUXOKIBJm/FpgO Q2Rg== X-Gm-Message-State: APjAAAWwJJ9j0PUqhvl8LXAfgzQC4jbC/s0SFweUiV6RXxokEhouoKqR V/6rNyvsrod4O0LL5ZAu7oRAAQ== X-Google-Smtp-Source: APXvYqw+1C1Pvr11q8AONS2td9iwm6bodbUuuJy7w3SrM1wrQki8aRt57kKphgwrMCqqnWG+ZJDomQ== X-Received: by 2002:aa7:cdd6:: with SMTP id h22mr34660703edw.132.1570545878559; Tue, 08 Oct 2019 07:44:38 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id z20sm3957544edb.3.2019.10.08.07.44.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Oct 2019 07:44:37 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id 9DE6E10170F; Tue, 8 Oct 2019 17:44:37 +0300 (+03) Date: Tue, 8 Oct 2019 17:44:37 +0300 From: "Kirill A. Shutemov" To: Michal Hocko Cc: Vlastimil Babka , Yang Shi , kirill.shutemov@linux.intel.com, ktkhai@virtuozzo.com, hannes@cmpxchg.org, hughd@google.com, shakeelb@google.com, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: thp: move deferred split queue to memcg's nodeinfo Message-ID: <20191008144437.fr374cxtpnrnnjsv@box> References: <1569968203-64647-1-git-send-email-yang.shi@linux.alibaba.com> <20191002084304.GI15624@dhcp22.suse.cz> <30421920-4fdb-767a-6ef2-60187932c414@suse.cz> <20191007143030.GN2381@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191007143030.GN2381@dhcp22.suse.cz> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 07, 2019 at 04:30:30PM +0200, Michal Hocko wrote: > On Mon 07-10-19 16:19:59, Vlastimil Babka wrote: > > On 10/2/19 10:43 AM, Michal Hocko wrote: > > > On Wed 02-10-19 06:16:43, Yang Shi wrote: > > >> The commit 87eaceb3faa59b9b4d940ec9554ce251325d83fe ("mm: thp: make > > >> deferred split shrinker memcg aware") makes deferred split queue per > > >> memcg to resolve memcg pre-mature OOM problem. But, all nodes end up > > >> sharing the same queue instead of one queue per-node before the commit. > > >> It is not a big deal for memcg limit reclaim, but it may cause global > > >> kswapd shrink THPs from a different node. > > >> > > >> And, 0-day testing reported -19.6% regression of stress-ng's madvise > > >> test [1]. I didn't see that much regression on my test box (24 threads, > > >> 48GB memory, 2 nodes), with the same test (stress-ng --timeout 1 > > >> --metrics-brief --sequential 72 --class vm --exclude spawn,exec), I saw > > >> average -3% (run the same test 10 times then calculate the average since > > >> the test itself may have most 15% variation according to my test) > > >> regression sometimes (not every time, sometimes I didn't see regression > > >> at all). > > >> > > >> This might be caused by deferred split queue lock contention. With some > > >> configuration (i.e. just one root memcg) the lock contention my be worse > > >> than before (given 2 nodes, two locks are reduced to one lock). > > >> > > >> So, moving deferred split queue to memcg's nodeinfo to make it NUMA > > >> aware again. > > >> > > >> With this change stress-ng's madvise test shows average 4% improvement > > >> sometimes and I didn't see degradation anymore. > > > > > > My concern about this getting more and more complex > > > (http://lkml.kernel.org/r/20191002084014.GH15624@dhcp22.suse.cz) holds > > > here even more. Can we step back and reconsider the whole thing please? > > > > What about freeing immediately after split via workqueue and also have a > > synchronous version called before going oom? Maybe there would be also > > other things that would benefit from this scheme instead of traditional > > reclaim and shrinkers? > > That is exactly what we have discussed some time ago. Yes, I've posted the patch: http://lkml.kernel.org/r/20190827125911.boya23eowxhqmopa@box But I still not sure that the approach is right. I expect it to trigger performance regressions. For system with pleanty of free memory, we will just pay split cost for nothing in many cases. -- Kirill A. Shutemov