linux-kernel - Re: [RFC PATCH v3 1/2] cgroup: cgroup.freeze.stat.local time accounting

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Message-ID: <dbx8qzxe7kqu.fsf@ynaffit-andsys.c.googlers.com>
Date: Wed, 13 Aug 2025 18:30:33 -0700
From: Tiffany Yang <ynaffit@...gle.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-kernel@...r.kernel.org, John Stultz <jstultz@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Stephen Boyd <sboyd@...nel.org>, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, "Michal Koutný" <mkoutny@...e.com>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Chen Ridong <chenridong@...wei.com>, 
	kernel-team@...roid.com, Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, 
	cgroups@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH v3 1/2] cgroup: cgroup.freeze.stat.local time accounting

Tejun Heo <tj@...nel.org> writes:

> Hello,

> Generally looks good to me. Some comments on cosmetics / interface.

> On Mon, Aug 04, 2025 at 08:29:41PM -0700, Tiffany Yang wrote:
> ...
>> +  cgroup.freeze.stat.local

> This was mentioned before and maybe I missed the following discussions but
> given that cgroup.freeze is a part of core cgroup, cgroup.stat.local is
> probably the right place. It's not great that cgroup.stat wouldn't be a
> superset of cgroup.stat.local but we can add the hierarchical counter  
> later
> if necessary.

Got it. I had ended up opting for the "freeze"-specific name because
there was already a cgroup_local_stat_show that seemed to imply that
cgroup.stat.local was reserved for controllers with a struct
cgroup_subsys. I will update v4 with something similar for core!


>> +	A read-only flat-keyed file which exists in non-root cgroups.
>> +	The following entry is defined:
>> +
>> +	  freeze_time_total

> How about just frozen_usec? "_usec" is what we used in cpu.stat for time
> stats.

Ack.


>> +		Cumulative time that this cgroup has spent between freezing and
>> +		thawing, regardless of whether by self or ancestor groups.
>> +		NB: (not) reaching "frozen" state is not accounted here.
>> +
>> +		Using the following ASCII representation of a cgroup's freezer
>> +		state, ::

> It's a bit odd to include credit in a doc file. Maybe move it to the
> description or add Co-developed-by: tag?


Will do! Thanks for looking over this :).

-- 
Tiffany Y. Yang