linux-kernel - Re: [PATCH v2 3/3] cgroup/rstat: Add run

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3wqaz6jb74i2cdtvkv4isvhapiiqukyicuol76s66xwixlaz3c@qr6bva3wbxkx>
Date: Mon, 27 Jan 2025 15:10:02 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Abel Wu <wuyun.abel@...edance.com>
Cc: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Yury Norov <yury.norov@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Bitao Hu <yaoma@...ux.alibaba.com>, Chen Ridong <chenridong@...wei.com>, 
	"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] cgroup/rstat: Add run_delay accounting for cgroups

Hello.

On Sat, Jan 25, 2025 at 01:25:12PM +0800, Abel Wu <wuyun.abel@...edance.com> wrote:
> The per-task and per-cpu accounting have already been tracked by
> t->sched_info.run_delay and rq->rq_sched_info.run_delay respectively.
> Extends this to also include cgroups.
> 
> The PSI indicator, "some" of cpu.pressure, loses the insight into how
> severely that cgroup is stalled. Say 100 tasks or just 1 task that gets
> stalled at a certain point will show no difference in "some" pressure.
> IOW "some" is a flat value that not weighted by the severity (e.g. # of
> tasks).

IIUC below are three examples of when "some" tasks are waiting for CPU:

a)
  t1 |----|
  t2 |xx--|

b)
  t1 |----|
  t2 |x---|
  t3 |-x--|

c)
  t1 |----|
  t2 |xx--|
  t3 |xx--|

(- means runnable on CPU, x means runnable waiting on RQ)

Which pair from a), b), c) is indistinguishable via PSI? (Or can you
please add your illustrative example?)
And how do per-cgroup run_delay distinguishe those?


Thanks,
Michal

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)