From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: Re: [PATCH v2 6/8] mm/lru: remove rcu_read_lock to fix performance regression Date: Wed, 13 Nov 2019 11:40:46 +0000 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 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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