From: Yosry Ahmed <yosryahmed@google.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>,
Michal Hocko <mhocko@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2] mm: memcg: use rstat for non-hierarchical stats
Date: Wed, 26 Jul 2023 08:23:28 -0700 [thread overview]
Message-ID: <CAJD7tkb6SmCDLDSCciPfXGK7Z_zyr4vh_XKvhysL6pci88WjKw@mail.gmail.com> (raw)
In-Reply-To: <20230726152055.GC1365610@cmpxchg.org>
On Wed, Jul 26, 2023 at 8:20 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Tue, Jul 25, 2023 at 07:20:02PM -0700, Yosry Ahmed wrote:
> > On Tue, Jul 25, 2023 at 7:15 PM Roman Gushchin <roman.gushchin@linux.dev> wrote:
> > >
> > > On Wed, Jul 26, 2023 at 12:29:04AM +0000, Yosry Ahmed wrote:
> > > > Currently, memcg uses rstat to maintain hierarchical stats. Counters are
> > > > maintained for hierarchical stats at each memcg. Rstat tracks which
> > > > cgroups have updates on which cpus to keep those counters fresh on the
> > > > read-side.
> > > >
> > > > For non-hierarchical stats, we do not maintain counters. Instead, the
> > > global?
> >
> > Do you mean "we do not maintain global counters"? I think "global" is
> > confusing, because it can be thought of as all cpus or as including
> > the subtree (as opposed to local for non-hierarchical stats).
>
> "global" seems fine to me, I don't think it's ambiguous in the direct
> comparison with per-cpu counts.
>
> Alternatively, rephrase the whole thing? Something like:
>
> "Non-hierarchical stats are currently not covered by rstat. Their
> per-cpu counters are summed up on every read, which is expensive."
Rephrasing sounds good to me.
I will send a v3 with the correct commit log and collected Acks to
make Andrew's life easier.
prev parent reply other threads:[~2023-07-26 15:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-26 0:29 [PATCH] " Yosry Ahmed
2023-07-26 0:29 ` [PATCH v2] " Yosry Ahmed
2023-07-26 0:36 ` Yosry Ahmed
2023-07-26 15:13 ` Johannes Weiner
2023-07-26 15:14 ` Yosry Ahmed
2023-07-26 2:15 ` Roman Gushchin
2023-07-26 2:20 ` Yosry Ahmed
2023-07-26 15:20 ` Johannes Weiner
2023-07-26 15:23 ` Yosry Ahmed [this message]
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