From: Yosry Ahmed <yosryahmed@google.com>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Michal Hocko <mhocko@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Ivan Babrou <ivan@cloudflare.com>, Tejun Heo <tj@kernel.org>,
Waiman Long <longman@redhat.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/4] mm: memcg: let non-unified root stats flushes help unified flushes
Date: Tue, 5 Sep 2023 08:54:46 -0700 [thread overview]
Message-ID: <CAJD7tkaHVtMiMYFocNiABuyhPcqt77gei0UeaDq4J7V-=tMFYA@mail.gmail.com> (raw)
In-Reply-To: <hrpw2bjsrs3pzxympb7cz4nohyeztnxkmdtzbzlfdba6ugkken@dhcdbbbrv4fn>
On Tue, Sep 5, 2023 at 7:10 AM Michal Koutný <mkoutny@suse.com> wrote:
>
> On Mon, Sep 04, 2023 at 05:41:10PM +0200, Michal Hocko <mhocko@suse.com> wrote:
> > So it also creates an undocumented but userspace visible behavior.
> > Something that userspace might start depending on, right?
>
> Yes but -
> - depending on undocumented behavior is a mistake,
> - breaking the dependency would manifest (in the case I imagine) as a
> performance regression (and if there are some users, the future can
> allow them configuring periodic kernel flush to compensate for that).
I think I am missing something. This change basically makes userspace
readers (for the root memcg) help out unified flushers, which are
in-kernel readers (e.g. reclaim) -- not the other way around.
How would that create a userspace visible behavior that a dependency
can be formed on? Users expecting reclaim to be faster right after
reading root stats? I would guess that would be too flaky to cause a
behavior that people can depend on tbh.
next prev parent reply other threads:[~2023-09-05 15:55 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 16:56 [PATCH v4 0/4] memcg: non-unified flushing for userspace stats Yosry Ahmed
2023-08-31 16:56 ` [PATCH v4 1/4] mm: memcg: properly name and document unified stats flushing Yosry Ahmed
2023-09-04 14:44 ` Michal Hocko
2023-09-05 15:55 ` Yosry Ahmed
2023-08-31 16:56 ` [PATCH v4 2/4] mm: memcg: add a helper for non-unified " Yosry Ahmed
2023-09-04 14:45 ` Michal Hocko
2023-08-31 16:56 ` [PATCH v4 3/4] mm: memcg: let non-unified root stats flushes help unified flushes Yosry Ahmed
2023-09-04 14:50 ` Michal Hocko
2023-09-04 15:29 ` Michal Koutný
2023-09-04 15:41 ` Michal Hocko
2023-09-05 14:10 ` Michal Koutný
2023-09-05 15:54 ` Yosry Ahmed [this message]
2023-09-05 16:07 ` Michal Koutný
2023-09-12 11:03 ` Michal Hocko
2023-08-31 16:56 ` [PATCH v4 4/4] mm: memcg: use non-unified stats flushing for userspace reads Yosry Ahmed
2023-09-04 15:15 ` Michal Hocko
2023-09-05 15:57 ` Yosry Ahmed
2023-09-08 0:52 ` Wei Xu
2023-09-08 1:02 ` Ivan Babrou
2023-09-08 1:11 ` Yosry Ahmed
2023-09-11 13:11 ` Michal Hocko
2023-09-11 19:15 ` Wei Xu
2023-09-11 19:34 ` Michal Hocko
2023-09-11 20:01 ` Wei Xu
2023-09-11 20:21 ` Tejun Heo
2023-09-11 20:28 ` Yosry Ahmed
2023-09-12 11:03 ` Michal Hocko
2023-09-12 11:09 ` Yosry Ahmed
2023-08-31 17:18 ` [PATCH v4 0/4] memcg: non-unified flushing for userspace stats Waiman Long
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