From: Shakeel Butt <shakeelb@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: mkoutny@suse.com, cgroups@vger.kernel.org, hannes@cmpxchg.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
mhocko@kernel.org
Subject: Re: [PATCH v2 1/2] memcg: flush stats only if updated
Date: Thu, 4 Nov 2021 15:09:18 -0700 [thread overview]
Message-ID: <CALvZod5xT2Mi2wktD-OTS0xkChNzArnMCLBNy7cg0dVupSOhXw@mail.gmail.com> (raw)
In-Reply-To: <20211104142751.5ab290d5cf4be1749c9c87ed@linux-foundation.org>
On Thu, Nov 4, 2021 at 2:27 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Thu, 14 Oct 2021 09:31:46 -0700 Shakeel Butt <shakeelb@google.com> wrote:
>
> > Hi Michal,
> >
> > On Wed, Oct 13, 2021 at 11:01 AM Michal Koutný <mkoutny@suse.com> wrote:
> > >
> > > On Fri, Oct 01, 2021 at 12:00:39PM -0700, Shakeel Butt <shakeelb@google.com> wrote:
> > > > In this patch we kept the stats update codepath very minimal and let the
> > > > stats reader side to flush the stats only when the updates are over a
> > > > specific threshold. For now the threshold is (nr_cpus * CHARGE_BATCH).
> > >
> > > BTW, a noob question -- are the updates always single page sized?
> > >
> > > This is motivated by apples vs oranges comparison since the
> > > nr_cpus * MEMCG_CHARGE_BATCH
> > > suggests what could the expected error be in pages (bytes). But it's mostly
> > > wrong since: a) uncertain single-page updates, b) various counter
> > > updates summed together. I wonder whether the formula can serve to
> > > provide at least some (upper) estimate.
> > >
> >
> > Thanks for your review. This forces me to think more on this because each
> > update does not necessarily be a single page sized update e.g. adding a hugepage
> > to an LRU.
> >
> > Though I think the error is time bounded by 2 seconds but in those 2 seconds
> > mathematically the error can be large.
>
> Sounds significant?
Yes it can be.
>
> > What do you think of the following
> > change? It will bound the error better within the 2 seconds window.
>
> This didn't seem to go anywhere. I'll send "memcg: flush stats only if
> updated" Linuswards, but please remember to resurrect this idea soonish
> (this month?) if you think such a change is desirable.
>
Yes, I will follow up on this soon.
prev parent reply other threads:[~2021-11-04 22:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-01 19:00 [PATCH v2 1/2] memcg: flush stats only if updated Shakeel Butt
2021-10-01 19:00 ` [PATCH v2 2/2] memcg: unify memcg stat flushing Shakeel Butt
2021-10-13 18:01 ` Michal Koutný
2021-10-13 19:24 ` Shakeel Butt
2021-10-14 9:04 ` Michal Koutný
2021-10-13 18:01 ` [PATCH v2 1/2] memcg: flush stats only if updated Michal Koutný
2021-10-14 16:31 ` Shakeel Butt
2021-10-15 17:55 ` Michal Koutný
2021-11-04 21:27 ` Andrew Morton
2021-11-04 22:09 ` Shakeel Butt [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CALvZod5xT2Mi2wktD-OTS0xkChNzArnMCLBNy7cg0dVupSOhXw@mail.gmail.com \
--to=shakeelb@google.com \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mkoutny@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).