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=-11.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 BDBAECA9EAE for ; Wed, 30 Oct 2019 01:15:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8F0D320866 for ; Wed, 30 Oct 2019 01:15:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ijhbZvY9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726952AbfJ3BP6 (ORCPT ); Tue, 29 Oct 2019 21:15:58 -0400 Received: from mail-oi1-f196.google.com ([209.85.167.196]:35308 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726401AbfJ3BP6 (ORCPT ); Tue, 29 Oct 2019 21:15:58 -0400 Received: by mail-oi1-f196.google.com with SMTP id n16so582317oig.2 for ; Tue, 29 Oct 2019 18:15:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=LiqlPgdWNA9PRH5nALR1HXVaery8pdVvA3tw4kzK/YM=; b=ijhbZvY9UqNfl0f+NlEf8kzcArGh2+O1V9Qyky+fDyrgw8qLP+bg/s3HN8MX+NgmFB 6ctonOUgLG+wTHzSpztuBoRdS0j54g1mHoCUILtMOFrbAxGLzGLHrSkzQUTAiFxmFkFj 3K1QzMK204kj5hxRODEPadXlLDnQh7EhcScbGDIYs+Aaoen4DZ3FUeva+HtFFAwiJwXG tCSu1/ACld++aea1lShqC9oBbwZRFkDo+nMkk4b+hkKrL4ZjzXEo0hAkvRq4zJPNmxd/ QpvtC5qB+hCjmQLyhrsoHmf1a/NJM5Lvb3kUurBZu4oxL07nAopxGqf9ctSUP1Y3WxaU JjMw== 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=LiqlPgdWNA9PRH5nALR1HXVaery8pdVvA3tw4kzK/YM=; b=DRCjCYwn9qE0br9jJfsojYnKge/ubDQsxG7gku9TN4wBGSWnEfNBTcM0IMtOHTGk5D 51EPdtq3nIxNS9uGQMgiSV0ogzSrPRW1I6u4t+GF8Eov7sN4D8cyeeIdNwMmx3iXNLdx NFCA50Iemca2EkU9f698vDhk2h55TCivG8/9XUeyzQRfJ5/b1VgGIgrp1df8nr6FYpNR L2H6RcQepa04m0B3kUDKK/+VTsdQOMWOgF7wdRuAGkDeJBYsXBbonngMGY1frM3lz005 f3pevoM/RXQfYFidqPo39PRyieVoFQCXDE5smE/xzdv9eRGptm5nBjihpkGXyQvib+r5 mzCg== X-Gm-Message-State: APjAAAXiEIr5ZBPRNdwdWkXRNZmZxODxN3buiAn+IMPxVT8OliYV0H82 hnZbdpfeMqzDYUUMnpjzoP6k1tPynuCJYZN+t8x5cA== X-Google-Smtp-Source: APXvYqxTGzbhYMHFytIpfUMi/ukV5/jH9kboBUiKZ1WFs7zogXKc9XtsF+q5eu/WJlvrcJe/MwmVgS+vqiIjiRFYCRs= X-Received: by 2002:aca:180e:: with SMTP id h14mr6309696oih.142.1572398156861; Tue, 29 Oct 2019 18:15:56 -0700 (PDT) MIME-Version: 1.0 References: <20191029234753.224143-1-shakeelb@google.com> <20191029175459.b3bfed9326559e69acdd2e35@linux-foundation.org> In-Reply-To: <20191029175459.b3bfed9326559e69acdd2e35@linux-foundation.org> From: Shakeel Butt Date: Tue, 29 Oct 2019 18:15:45 -0700 Message-ID: Subject: Re: [PATCH] mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node() To: Andrew Morton Cc: Greg Thelen , Roman Gushchin , Johannes Weiner , Michal Hocko , Linux MM , Cgroups , LKML , syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 29, 2019 at 5:55 PM Andrew Morton wrote: > > On Tue, 29 Oct 2019 16:47:53 -0700 Shakeel Butt wrote: > > > Since commit 1ba6fc9af35b ("mm: vmscan: do not share cgroup iteration > > between reclaimers"), the memcg reclaim does not bail out earlier based > > on sc->nr_reclaimed and will traverse all the nodes. All the reclaimable > > pages of the memcg on all the nodes will be scanned relative to the > > reclaim priority. So, there is no need to maintain state regarding which > > node to start the memcg reclaim from. Also KCSAN complains data races in > > the code maintaining the state. > > > > This patch effectively reverts the commit 889976dbcb12 ("memcg: reclaim > > memory from nodes in round-robin order") and the commit 453a9bf347f1 > > ("memcg: fix numa scan information update to be triggered by memory > > event"). > > > > Signed-off-by: Shakeel Butt > > Reported-by: > > I can't find the original sysbot email. Help? > > iirc the incidentally-fixed issue is a rather theoretical data race and > the patch isn't a high priority thing? > Let me check why the link is not working. However you are right that the fix is for a theoretical data race and no need to be backported to stable trees. Shakeel