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_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 27408C432C0 for ; Tue, 26 Nov 2019 03:52:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B87232071A for ; Tue, 26 Nov 2019 03:52:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="b9tBm/ON" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B87232071A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1B0EB6B02B8; Mon, 25 Nov 2019 22:52:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 162876B02BA; Mon, 25 Nov 2019 22:52:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 050B06B02BB; Mon, 25 Nov 2019 22:52:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0070.hostedemail.com [216.40.44.70]) by kanga.kvack.org (Postfix) with ESMTP id E11E96B02B8 for ; Mon, 25 Nov 2019 22:52:56 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 8678A2C96 for ; Tue, 26 Nov 2019 03:52:56 +0000 (UTC) X-FDA: 76197057552.15.level50_36bd5f1881555 X-HE-Tag: level50_36bd5f1881555 X-Filterd-Recvd-Size: 4595 Received: from mail-io1-f67.google.com (mail-io1-f67.google.com [209.85.166.67]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Tue, 26 Nov 2019 03:52:56 +0000 (UTC) Received: by mail-io1-f67.google.com with SMTP id b26so17015438ion.7 for ; Mon, 25 Nov 2019 19:52:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5eCkizbFXOABShf2G81jyFye/8X0Bx34QjnEZBqd7UI=; b=b9tBm/ONcvhCebruLMqthtvyQtv7Re2y7swfJxPuYpRZWLZX7Lj9/cuY6qagHfHDah 8/Ey0e/rH+Yzb7E1bEI/3R6/3JEYXEfZfC+cD/gO+xPDR18RNn/V9/ynjXPiSbvsC9EO WHRGodLQ3gmguBisoEagJLMPwjM3D3QpK8tQcqHbfYPyfdcsjkIz8BeY/xZS6r/1YaAx +rPHfXsSVOqlQCxwQvEIF5q5Kk1UyMNW7SIdmTSHU+Oqxft/lBu1oJq67CZRF5dLTTi0 WoPvf5HZo06dbN3rTVFU6dutxXiqJ1e0AEhXEWqtRUlPM09rfL686zn/KDgT8RBKdwu7 7BOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5eCkizbFXOABShf2G81jyFye/8X0Bx34QjnEZBqd7UI=; b=XWP5VUhzf3Z0pngiKgKRIAyxM3ZebjLh8Psy7gLv95evqW2Q2iuuckehOJcvwRSNP2 sIIMz1ZR0rkoA7h9jyhO8WsRRPXnGTtZMwsEw++LZJS2KtvFNd95H615oBM+XC7U53QH 3Uoeqtz11baHJZN8tsAqleTKjydr94bkyt6HXyp1UGenuY3NsX2v2c674xGyx2UjQRoy dYMk+BvPuQgMZ0SzD0EvV7KajjcR9xWeGy30GGiJ96XjdpPvtW0lElIBoCCHuVS0dhvt VnDHrl8OY/29Zcqb1RVtJHFzf2tDuLIYVOpQlI3VPiktF/aimmJnRNP8/ZyMCe+jwc0P aOqw== X-Gm-Message-State: APjAAAWBFG6+eCwEJRCemQiagoChq6GVG9sj2qPSyJ/rmKEBQRAGyuMP iA+k0dIbIrIQqZUIp2K0+I5/jwvWa6kDh8VW+80= X-Google-Smtp-Source: APXvYqyCLsZ6lnt9Nca3sOGQJc8OI7SxUG4vwKp/6IvU/GsbmZgxYZSYPI4mc6QUKbGiv1t0eDAQ64zvwN9hnysvV4E= X-Received: by 2002:a5d:8953:: with SMTP id b19mr2738037iot.168.1574740375327; Mon, 25 Nov 2019 19:52:55 -0800 (PST) MIME-Version: 1.0 References: <1574676893-1571-1-git-send-email-laoar.shao@gmail.com> <20191125110848.GH31714@dhcp22.suse.cz> <20191125115409.GJ31714@dhcp22.suse.cz> <20191125123123.GL31714@dhcp22.suse.cz> <20191125124553.GM31714@dhcp22.suse.cz> <20191125142150.GP31714@dhcp22.suse.cz> <20191125144213.GB602168@cmpxchg.org> In-Reply-To: <20191125144213.GB602168@cmpxchg.org> From: Yafang Shao Date: Tue, 26 Nov 2019 11:52:19 +0800 Message-ID: Subject: Re: [PATCH] mm, memcg: clear page protection when memcg oom group happens To: Johannes Weiner Cc: Michal Hocko , Vladimir Davydov , Andrew Morton , Linux MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 25, 2019 at 10:42 PM Johannes Weiner wrote: > > On Mon, Nov 25, 2019 at 03:21:50PM +0100, Michal Hocko wrote: > > On Mon 25-11-19 22:11:15, Yafang Shao wrote: > > > When there're no processes, we don't need to protect the pages. You > > > can consider it as 'fault tolerance' . > > > > I have already tried to explain why this is a bold statement that > > doesn't really hold universally and that the kernel doesn't really have > > enough information to make an educated guess. > > I agree, this is not obviously true. And the kernel shouldn't try to > guess whether the explicit userspace configuration is still desirable > to userspace or not. Should we also delete the cgroup when it becomes > empty for example? > > It's better to implement these kinds of policy decisions from > userspace. > > There is a cgroup.events file that can be polled, and its "populated" > field shows conveniently whether there are tasks in a subtree or > not. You can use that to clear protection settings. Why isn't force_empty supported in cgroup2 ? In this case we can free the protected file pages immdiately with force_empty. The advantage of it is to avoid scaning all other memcgs in kswapd/direct reclaim paths, because currently the reclaimer will fairly scan all memcgs and reclaim pages from them. What's the problem with force_empty ? Thanks Yafang