linux-kernel - Re: [PATCH v3 1/2] cgroup: Show # of subsystem CSSes in cgroup.stat

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Message-ID: <a033dc74-2362-40f1-a091-b8bf22a8d3cb@redhat.com>
Date: Thu, 11 Jul 2024 15:29:56 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Zefan Li <lizefan.x@...edance.com>,
 Jonathan Corbet <corbet@....net>, cgroups@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Kamalesh Babulal <kamalesh.babulal@...cle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [PATCH v3 1/2] cgroup: Show # of subsystem CSSes in cgroup.stat


On 7/11/24 15:21, Tejun Heo wrote:
> Hello,
>
> On Thu, Jul 11, 2024 at 03:13:12PM -0400, Waiman Long wrote:
>> That will means cgroup subsystems that are seldomly used like rdma, misc or
>> even hugetlb will always be shown in all the cgroup.stat output. I actually
> Hmm... yeah, that does increase the amount of output, but I don't know. The
> trade-off is between consistency and brevity and I think I'd go for
> consistency here.
>
>> prefer just showing those that are enabled. As for dying memory cgroups,
>> they will only be shown in its online ancestors. We currently don't know how
> So, one peculiarity with memory is that when you enable io, it gets
> implicitly enabled together and we likely wanna show that.

If memory is implicitly enabled, it is treated as enabled as the 
corresponding cgroup->subsys[] entry should be set. I currently don't 
filter out those in the cgrp_dfl_implicit_ss_mask. So perf_event, which 
is implicitly enabled, is shown in all the cgroup.stat.

If you still want to display all even if some of them are not enabled, I 
can certainly do that.

Cheers,
Longman