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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 99179C17447 for ; Wed, 13 Nov 2019 11:40:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3B96A222C9 for ; Wed, 13 Nov 2019 11:40:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3B96A222C9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9B0186B0005; Wed, 13 Nov 2019 06:40:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 961326B0006; Wed, 13 Nov 2019 06:40:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8503B6B0007; Wed, 13 Nov 2019 06:40:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id 6F7A66B0005 for ; Wed, 13 Nov 2019 06:40:51 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 150E9180AD82F for ; Wed, 13 Nov 2019 11:40:51 +0000 (UTC) X-FDA: 76151062302.20.flock79_2473454ffad5b X-HE-Tag: flock79_2473454ffad5b X-Filterd-Recvd-Size: 3177 Received: from outbound-smtp05.blacknight.com (outbound-smtp05.blacknight.com [81.17.249.38]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 Nov 2019 11:40:50 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp05.blacknight.com (Postfix) with ESMTPS id 8F9BE9892E for ; Wed, 13 Nov 2019 11:40:48 +0000 (GMT) Received: (qmail 2036 invoked from network); 13 Nov 2019 11:40:48 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.18.57]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 13 Nov 2019 11:40:48 -0000 Date: Wed, 13 Nov 2019 11:40:46 +0000 From: Mel Gorman To: Alex Shi Cc: Matthew Wilcox , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com, Johannes Weiner , Roman Gushchin , Shakeel Butt , Chris Down , Thomas Gleixner Subject: Re: [PATCH v2 6/8] mm/lru: remove rcu_read_lock to fix performance regression Message-ID: <20191113114045.GZ3016@techsingularity.net> References: <1573567588-47048-1-git-send-email-alex.shi@linux.alibaba.com> <1573567588-47048-7-git-send-email-alex.shi@linux.alibaba.com> <20191112143844.GB7934@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed, Nov 13, 2019 at 10:40:58AM +0800, Alex Shi wrote: > > > ?? 2019/11/12 ????10:38, Matthew Wilcox ????: > > On Tue, Nov 12, 2019 at 10:06:26PM +0800, Alex Shi wrote: > >> Intel 0day report there are performance regression on this patchset. > >> The detailed info points to rcu_read_lock + PROVE_LOCKING which causes > >> queued_spin_lock_slowpath waiting too long time to get lock. > >> Remove rcu_read_lock is safe here since we had a spinlock hold. > > Argh. You have not sent these patches in a properly reviewable form! > > I wasted all that time reviewing the earlier patch in this series only to > > find out that you changed it here. FIX THE PATCH, don't send a fix-patch > > on top of it! > > > > Hi Matthew, > > Very sorry for your time! The main reasons I use a separate patch since a, Intel 0day asking me to credit their are founding, and I don't know how to give a clearly/elegant explanation for a non-exist regression in a fixed patch. b, this regression is kindly pretty tricky. Maybe it's better saying thanks in version change log of cover-letter? > Add something like this to the patch [lkp@intel.com: Fix RCU-related regression reported by LKP robot] Signed-off-by: Alex Shi ... -- Mel Gorman SUSE Labs