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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9110BCA9EAE for ; Wed, 30 Oct 2019 00:55:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4549F2086A for ; Wed, 30 Oct 2019 00:55:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="z6JxpYIA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4549F2086A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DE1EE6B0003; Tue, 29 Oct 2019 20:55:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D92636B0006; Tue, 29 Oct 2019 20:55:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CA7E76B0007; Tue, 29 Oct 2019 20:55:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0042.hostedemail.com [216.40.44.42]) by kanga.kvack.org (Postfix) with ESMTP id A257C6B0003 for ; Tue, 29 Oct 2019 20:55:01 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 33350824999B for ; Wed, 30 Oct 2019 00:55:01 +0000 (UTC) X-FDA: 76098631602.11.flesh06_83181177e1f2c X-HE-Tag: flesh06_83181177e1f2c X-Filterd-Recvd-Size: 2806 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Wed, 30 Oct 2019 00:55:00 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A43E220862; Wed, 30 Oct 2019 00:54:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572396900; bh=tFF8Zjgmu+WIIlTlxCMd0FFO5WyZqnXX4sv24/2yUUc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=z6JxpYIAXwYaitOroIOgVkFFJ+fD7w974Y/gOcL+K9o7d1P1lWTu08tW16aKNpUvw y+t/MUhPzHfbuARnFWHe6PZgDfV3SiJMRkW2/CE4taPh37lj9lpTCJutLLoo1fzGnY M/E0EaPON/9wkaV7L85UXF+LEpMHvI7mmNWumlTY= Date: Tue, 29 Oct 2019 17:54:59 -0700 From: Andrew Morton To: Shakeel Butt Cc: Greg Thelen , Roman Gushchin , Johannes Weiner , Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com Subject: Re: [PATCH] mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node() Message-Id: <20191029175459.b3bfed9326559e69acdd2e35@linux-foundation.org> In-Reply-To: <20191029234753.224143-1-shakeelb@google.com> References: <20191029234753.224143-1-shakeelb@google.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 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?