From: Li Wang <liwang@redhat.com>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Waiman Long <longman@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Shuah Khan <shuah@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
Sean Christopherson <seanjc@google.com>,
James Houghton <jthoughton@google.com>,
Sebastian Chlad <sebastianchlad@gmail.com>,
Guopeng Zhang <zhangguopeng@kylinos.cn>,
Li Wang <liwan@redhat.com>
Subject: Re: [PATCH v2 1/7] memcg: Scale up vmstats flush threshold with int_sqrt(nr_cpus+2)
Date: Thu, 2 Apr 2026 18:19:56 +0800 [thread overview]
Message-ID: <ac5CzJ5S0kp71rrs@redhat.com> (raw)
In-Reply-To: <ac42aIDVaGim5moO@redhat.com>
> > with kernel functions:
> > var1 = 65536*nr_cpus / (45426 * ilog2(nr_cpus) + 65536)
> > var2 = DIV_ROUND_UP(65536*nr_cpus, 45426 * ilog2(nr_cpus) + 65536)
> > var3 = roundup_pow_of_two(var2)
Consider a 1024-CPU machine with a cpuset-constrained cgroup using only 2 CPUs.
Its unavoidable batching error is just 2MB, yet the global threshold imposes
256MB (harmonic-mean) or 32MB (sqrt) of additional error — 128x and 16x
overprovisioning respectively. Both overshoot, but sqrt stays bit closer to
the ideal.
--
Regards,
Li Wang
next prev parent reply other threads:[~2026-04-02 10:20 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 20:42 [PATCH v2 0/7] selftests: memcg: Fix test_memcontrol test failures with large page sizes Waiman Long
2026-03-20 20:42 ` [PATCH v2 1/7] memcg: Scale up vmstats flush threshold with int_sqrt(nr_cpus+2) Waiman Long
2026-03-23 12:46 ` Li Wang
2026-03-24 0:15 ` Yosry Ahmed
2026-03-25 16:47 ` Waiman Long
2026-03-25 17:23 ` Yosry Ahmed
2026-04-01 18:41 ` Michal Koutný
2026-04-02 9:27 ` Li Wang
2026-04-02 10:19 ` Li Wang [this message]
2026-03-20 20:42 ` [PATCH v2 2/7] memcg: Scale down MEMCG_CHARGE_BATCH with increase in PAGE_SIZE Waiman Long
2026-03-23 12:47 ` Li Wang
2026-03-24 0:17 ` Yosry Ahmed
2026-03-20 20:42 ` [PATCH v2 3/7] selftests: memcg: Iterate pages based on the actual page size Waiman Long
2026-03-23 2:53 ` Li Wang
2026-03-23 2:56 ` Li Wang
2026-03-25 3:33 ` Waiman Long
2026-03-20 20:42 ` [PATCH v2 4/7] selftests: memcg: Increase error tolerance in accordance with " Waiman Long
2026-03-23 8:01 ` Li Wang
2026-03-25 16:42 ` Waiman Long
2026-03-20 20:42 ` [PATCH v2 5/7] selftests: memcg: Reduce the expected swap.peak with larger " Waiman Long
2026-03-23 8:24 ` Li Wang
2026-03-25 3:47 ` Waiman Long
2026-03-20 20:42 ` [PATCH v2 6/7] selftests: memcg: Don't call reclaim_until() if already in target Waiman Long
2026-03-23 8:53 ` Li Wang
2026-03-20 20:42 ` [PATCH v2 7/7] selftests: memcg: Treat failure for zeroing sock in test_memcg_sock as XFAIL Waiman Long
2026-03-23 9:44 ` Li Wang
2026-03-21 1:16 ` [PATCH v2 0/7] selftests: memcg: Fix test_memcontrol test failures with large page sizes Andrew Morton
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=ac5CzJ5S0kp71rrs@redhat.com \
--to=liwang@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=jthoughton@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=liwan@redhat.com \
--cc=longman@redhat.com \
--cc=mhocko@kernel.org \
--cc=mkoutny@suse.com \
--cc=muchun.song@linux.dev \
--cc=roman.gushchin@linux.dev \
--cc=rppt@kernel.org \
--cc=seanjc@google.com \
--cc=sebastianchlad@gmail.com \
--cc=shakeel.butt@linux.dev \
--cc=shuah@kernel.org \
--cc=tj@kernel.org \
--cc=zhangguopeng@kylinos.cn \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.