From: Johannes Weiner <hannes@cmpxchg.org>
To: Wei Xu <weixugc@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Michal Hocko <mhocko@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>, Tejun Heo <tj@kernel.org>,
Zefan Li <lizefan.x@bytedance.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
cgroups@vger.kernel.org, linux-doc@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Jonathan Corbet <corbet@lwn.net>,
Yu Zhao <yuzhao@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Greg Thelen <gthelen@google.com>
Subject: Re: [PATCH resend] memcg: introduce per-memcg reclaim interface
Date: Fri, 1 Apr 2022 17:07:32 -0400 [thread overview]
Message-ID: <YkdplNIhtz3iyLKv@cmpxchg.org> (raw)
In-Reply-To: <CAAPL-u-za-TTyyC5uMVev9eQyhxZS7q3pVqaUxCFjqk+Sv9+ig@mail.gmail.com>
On Fri, Apr 01, 2022 at 01:14:35PM -0700, Wei Xu wrote:
> On Fri, Apr 1, 2022 at 8:22 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
> > On Thu, Mar 31, 2022 at 09:05:15PM -0700, Wei Xu wrote:
> > > It is better to return an error code (e.g. -EBUSY) when
> > > memory_reclaim() fails to reclaim nr_to_reclaim bytes of memory,
> > > except if the cgroup memory usage is already 0. We can also return
> > > -EINVAL if nr_to_reclaim is too large (e.g. > limit).
> >
> > For -EBUSY, are you thinking of a specific usecase where that would
> > come in handy? I'm not really opposed to it, but couldn't convince
> > myself of the practical benefits of it, either.
> >
> > Keep in mind that MAX_RECLAIM_RETRIES failed reclaim attempts usually
> > constitute an OOM situation: memory.max will issue kills and
> > memory.high will begin crippling throttling. In what scenario would
> > you want to keep reclaiming a workload that is considered OOM?
> >
> > Certainly, proactive reclaim that wants to purge only the cold tail of
> > the workload wouldn't retry. Meta's version of this patch actually
> > does return -EAGAIN on reclaim failure, but the userspace daemon
> > doesn't do anything with it, so I didn't bring it up.
>
> -EAGAIN sounds good, too. Given that the userspace requests to
> reclaim a specified number of bytes, I think it is generally better to
> tell the userspace whether the request has been successfully
> fulfilled. Ideally, it would be even better to return how many bytes
> that have been reclaimed, though that is not easy to do through the
> cgroup interface. The userspace can choose to ignore the return value
> or log a message/update some stats (which Google does) for the
> monitoring purpose.
Fair enough, thanks for your thoughts. No objection from me!
next prev parent reply other threads:[~2022-04-01 21:07 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-31 8:41 [PATCH resend] memcg: introduce per-memcg reclaim interface Yosry Ahmed
2022-03-31 17:25 ` Roman Gushchin
2022-04-01 6:01 ` Wei Xu
2022-04-01 9:11 ` Yosry Ahmed
2022-04-01 18:39 ` Roman Gushchin
2022-04-01 21:13 ` Johannes Weiner
2022-04-01 21:21 ` Roman Gushchin
2022-04-01 21:38 ` Wei Xu
2022-04-01 21:51 ` Johannes Weiner
2022-04-04 17:14 ` Shakeel Butt
2022-04-04 17:13 ` Yosry Ahmed
2022-04-04 17:55 ` Roman Gushchin
2022-04-01 9:15 ` Yosry Ahmed
2022-04-01 15:41 ` Shakeel Butt
2022-04-01 13:49 ` Michal Hocko
2022-04-01 16:58 ` Roman Gushchin
2022-04-04 8:44 ` Michal Hocko
2022-04-04 18:25 ` Roman Gushchin
2022-03-31 19:25 ` Johannes Weiner
2022-04-01 0:33 ` Andrew Morton
2022-04-01 3:38 ` Wei Xu
2022-04-01 9:17 ` Yosry Ahmed
2022-04-01 13:03 ` Michal Hocko
2022-04-01 3:05 ` Chen Wandun
2022-04-01 9:20 ` Yosry Ahmed
2022-04-01 9:48 ` Chen Wandun
2022-04-01 10:02 ` Yosry Ahmed
2022-04-01 4:05 ` Wei Xu
2022-04-01 9:22 ` Yosry Ahmed
2022-04-01 15:22 ` Johannes Weiner
2022-04-01 20:14 ` Wei Xu
2022-04-01 21:07 ` Johannes Weiner [this message]
2022-04-04 17:08 ` Shakeel Butt
2022-04-05 2:30 ` Wei Xu
2022-04-05 10:09 ` Michal Koutný
2022-04-01 8:39 ` Vaibhav Jain
2022-04-01 9:23 ` Yosry Ahmed
2022-04-04 3:50 ` Vaibhav Jain
2022-04-04 17:18 ` Yosry Ahmed
2022-04-01 13:54 ` Michal Hocko
2022-04-01 16:56 ` Wei Xu
2022-04-02 8:13 ` Huang, Ying
2022-04-03 6:46 ` Wei Xu
2022-04-03 6:56 ` Wei Xu
2022-04-06 0:48 ` Huang, Ying
2022-04-06 1:07 ` Wei Xu
2022-04-06 2:49 ` Huang, Ying
2022-04-06 5:02 ` Wei Xu
2022-04-06 6:32 ` Huang, Ying
2022-04-06 7:05 ` Wei Xu
2022-04-06 8:49 ` Huang, Ying
2022-04-06 20:16 ` Wei Xu
2022-04-07 7:35 ` Michal Hocko
2022-04-07 21:26 ` Tim Chen
2022-04-07 22:12 ` Wei Xu
2022-04-07 23:11 ` Tim Chen
2022-04-08 2:10 ` Wei Xu
2022-04-08 3:08 ` Huang, Ying
2022-04-08 4:10 ` Wei Xu
2022-04-04 17:09 ` Yosry Ahmed
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