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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 B3135C433E0 for ; Mon, 6 Jul 2020 23:42:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 733A620720 for ; Mon, 6 Jul 2020 23:42:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="gf08immk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 733A620720 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 E1A9F6B002A; Mon, 6 Jul 2020 19:42:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DCAB56B002B; Mon, 6 Jul 2020 19:42:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D08036B002C; Mon, 6 Jul 2020 19:42:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0227.hostedemail.com [216.40.44.227]) by kanga.kvack.org (Postfix) with ESMTP id B86D66B002A for ; Mon, 6 Jul 2020 19:42:23 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 2021A2C84 for ; Mon, 6 Jul 2020 23:42:23 +0000 (UTC) X-FDA: 77009277366.08.snake09_411292a26eaf Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id ECC001819E621 for ; Mon, 6 Jul 2020 23:42:22 +0000 (UTC) X-HE-Tag: snake09_411292a26eaf X-Filterd-Recvd-Size: 3341 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Mon, 6 Jul 2020 23:42:22 +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 C1FD2206E9; Mon, 6 Jul 2020 23:42:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594078941; bh=t/nO/7PyzLhpBEiwo9upsXorfRn3O1Jz/2RyIvBEB5I=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gf08immkIY0zN6dKfIodzmcYTFcyBsLPgNlF2Zxveg00m2kfu570Aa8vSheBrB4qA 9sJr1So6ZaP888dMXSbmFZZBkTvpsdR/c4hRv1ONC3MVK9hG57f452K2n3Nr1i0YBs atWUXl54/p//1sVSBkLN7G/yaHRCgNxao2HHpZ5I= Date: Mon, 6 Jul 2020 16:42:20 -0700 From: Andrew Morton To: Andi Kleen Cc: Feng Tang , Qian Cai , Dennis Zhou , Tejun Heo , Christoph Lameter , kernel test robot , Michal Hocko , Johannes Weiner , Matthew Wilcox , Mel Gorman , Kees Cook , Luis Chamberlain , Iurii Zaikin , tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, lkp@lists.01.org Subject: Re: [mm] 4e2c82a409: ltp.overcommit_memory01.fail Message-Id: <20200706164220.cc73e53c7f1b285910c82807@linux-foundation.org> In-Reply-To: <20200706133434.GA3483883@tassilo.jf.intel.com> References: <20200705044454.GA90533@shbuild999.sh.intel.com> <20200705125854.GA66252@shbuild999.sh.intel.com> <20200705155232.GA608@lca.pw> <20200706014313.GB66252@shbuild999.sh.intel.com> <20200706023614.GA1231@lca.pw> <20200706132443.GA34488@shbuild999.sh.intel.com> <20200706133434.GA3483883@tassilo.jf.intel.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-Rspamd-Queue-Id: ECC001819E621 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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, 6 Jul 2020 06:34:34 -0700 Andi Kleen wrote: > > ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); > > - if (ret == 0 && write) > > + if (ret == 0 && write) { > > + if (sysctl_overcommit_memory == OVERCOMMIT_NEVER) > > + schedule_on_each_cpu(sync_overcommit_as); > > The schedule_on_each_cpu is not atomic, so the problem could still happen > in that window. > > I think it may be ok if it eventually resolves, but certainly needs > a comment explaining it. It sure does. The new exported-to-everything percpu_counter_sync() should have full formal documentation as well, please. > Can you do some stress testing toggling the > policy all the time on different CPUs and running the test on > other CPUs and see if the test fails? > > The other alternative would be to define some intermediate state > for the sysctl variable and only switch to never once the schedule_on_each_cpu > returned. But that's more complexity. > > > -Andi