From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH v2 1/3] mm: Fix dropped memcg from mem cgroup soft limit tree Date: Thu, 18 Feb 2021 20:13:05 +0100 Message-ID: References: <8d35206601ccf0e1fe021d24405b2a0c2f4e052f.1613584277.git.tim.c.chen@linux.intel.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1613675586; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2LEQzo8vyQpA89Pwawhl0KdWDVli2brjorL41NH4bg0=; b=q5SAQAr80eSFU1sPIy6CPtTyAaCdMpHwCM7Gkx4DMHmqb7iSUZx2XB3g4/RHdI4czipuk2 sGettzMqvcBp7SCmWZYw0Y5AcV8QnfUtNNaVuiascQ56cekbOUDDKk2RY/AWErk/j5iQ8c p2/P60C3SgKfPh9tyOlO+mt9MUgS07U= Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tim Chen Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , Dave Hansen , Ying Huang , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Thu 18-02-21 10:30:20, Tim Chen wrote: > > > On 2/18/21 12:24 AM, Michal Hocko wrote: > > > > > I have already acked this patch in the previous version along with Fixes > > tag. It seems that my review feedback has been completely ignored also > > for other patches in this series. > > Michal, > > My apology. Our mail system screwed up and there are some mail missing > from our mail system that I completely missed your mail. > Only saw them now after I looked into the lore.kernel.org. I see. My apology for suspecting you from ignoring my review. > Responding to your comment: > > >Have you observed this happening in the real life? I do agree that the > >threshold based updates of the tree is not ideal but the whole soft > >reclaim code is far from optimal. So why do we care only now? The > >feature is essentially dead and fine tuning it sounds like a step back > >to me. > > Yes, I did see the issue mentioned in patch 2 breaking soft limit > reclaim for cgroup v1. There are still some of our customers using > cgroup v1 so we will like to fix this if possible. It would be great to see more details. > For patch 3 regarding the uncharge_batch, it > is more of an observation that we should uncharge in batch of same node > and not prompted by actual workload. > Thinking more about this, the worst that could happen > is we could have some entries in the soft limit tree that overestimate > the memory used. The worst that could happen is a soft page reclaim > on that cgroup. The overhead from extra memcg event update could > be more than a soft page reclaim pass. So let's drop patch 3 > for now. I would still prefer to handle that in the soft limit reclaim path and check each memcg for the soft limit reclaim excess before the reclaim. > Let me know if you will like me to resend patch 1 with the fixes tag > for commit 4e41695356fb ("memory controller: soft limit reclaim on contention") > and if there are any changes I should make for patch 2. I will ack and suggest Fixes. > > Thanks. > > Tim -- Michal Hocko SUSE Labs