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Date: Mon, 12 Feb 2024 10:26:42 -0500
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Subject: Re: [PATCH v2] Port hierarchical_{memory,swap}_limit cgroup1->cgroup2
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To: =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>,
 "Jan Kratochvil (Azul)" <jkratochvil@azul.com>
Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
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 <ked455hccs23ghrqug3ieqck6qmmlip5htgszjvz7n3cvhvaeo@7kkg6faezy2a>
From: Waiman Long <longman@redhat.com>
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On 2/12/24 10:00, Michal Koutný wrote:
> Hello.
>
> Something like this would come quite handy.
>
> On Mon, Feb 12, 2024 at 12:10:38PM +0800, "Jan Kratochvil (Azul)" <jkratochvil@azul.com> wrote:
>> which are useful for userland to easily and performance-wise find out the
>> effective cgroup limits being applied.
> And the only way to figure out inside cgroupns.
>
>> But for cgroup2 it has been missing so far, this is just a copy-paste of the
>> cgroup1 code while changing s/memsw/swap/ as that is what cgroup1 vs. cgroup2
>> tracks. I have added it to the end of "memory.stat" to prevent possible
>> compatibility problems with existing code parsing that file.
> I was thinking of memory.max.effective (and others).
>
> - no need to (possibly flush) stats when reading memory.stat
> - can be generalized also for pids controller (and other "limiting" controllers)
> - analogous to precedent of cpuset.cpus.effective
>
> Whereas, using v1 approach in v2:
> - memory.stat mixes true stats and limits,
> - memmory.stat is hierarchical by default, no need for the prefix.
>
> What do you think of the separate .effective file(s)?

This is certainly a good alternative.

Cheers,
Longman