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From: Waiman Long <longman@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: "Michal Koutný" <mkoutny@suse.com>,
	"Zefan Li" <lizefan.x@bytedance.com>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Shuah Khan" <shuah@kernel.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Roman Gushchin" <guro@fb.com>, "Phil Auld" <pauld@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Marcelo Tosatti" <mtosatti@redhat.com>
Subject: Re: [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst
Date: Wed, 15 Dec 2021 13:55:05 -0500	[thread overview]
Message-ID: <58c06961-ffc4-27d7-01d2-4c91b0c9161d@redhat.com> (raw)
In-Reply-To: <Ybo1jmNvM6sblcJq@slm.duckdns.org>

On 12/15/21 13:35, Tejun Heo wrote:
> Hello, Waiman.
>
> On Wed, Dec 15, 2021 at 01:16:43PM -0500, Waiman Long wrote:
>> Allowing direct transition from member to invalid partition doesn't feel
>> right for me. A casual user may assume a partition is correctly formed
>> without double checking the "cpuset.partition" value. Returning an error
>> will prevent this kind of issue. If returning more information about the
>> failure is the main reason for allowing the invalid partition transition, we
>> can extend the "cpuset.partition" read syntax to also show the reason for
>> the previous failure.
> I don't think it's a good idea to display error messages without a way to
> link the error to the one who triggered it. This is the same problem we had
> with resettable counters. It only works for scenarios where one guy is
> sitting in front of the computer but gets nastry for more complex scnearios
> and automation.
Yes, I agree it is not a good way to handle this issue.
>
> I understand that allowing transitions to invalid state can feel jarring.
> There are pros and cons to both approaches. It's similar dynamics tho.
> Erroring out may be more intuitive for a casual user but makes it harder for
> more complex scenarios because whether a given operation errors or not is
> dependent on external asynchronous states, there's no good way of reporting
> the exact nature of the error or detecting when the operation would succeed
> in the future, and the error conditions are rather arbitrary.

Thanks for the explanation. Yes, there are always pros and cons for 
different approach to a problem. I am not totally against allowing 
member to invalid partition transition. In that case, reading back 
"cpuset.partition" is a must to verify that it is really a success.

How about we allow transition to an invalid partition state but still 
return an error?

Regards,
Longman


  reply	other threads:[~2021-12-15 18:55 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-05 18:32 [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-12-05 18:32 ` [PATCH v9 1/7] cgroup/cpuset: Don't let child cpusets restrict parent in default hierarchy Waiman Long
2021-12-13 20:41   ` Tejun Heo
2021-12-15 12:23     ` Michal Koutný
2021-12-15 17:59       ` Waiman Long
2021-12-17 15:48         ` [PATCH] cgroup/cpuset: Make child cpusets restrict parents on v1 hierarchy Michal Koutný
2021-12-17 16:34           ` Waiman Long
2022-01-12 21:25           ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 2/7] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective Waiman Long
2021-12-13 20:45   ` Tejun Heo
2021-12-15  3:24     ` Waiman Long
2021-12-15 10:36       ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 3/7] cgroup/cpuset: Refining features and constraints of a partition Waiman Long
2021-12-15 14:49   ` Michal Koutný
2021-12-15 16:29     ` Waiman Long
2021-12-16  9:28       ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 4/7] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2022-01-12 15:21   ` Peter Zijlstra
2022-01-12 15:40     ` Waiman Long
2022-01-12 21:23       ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 5/7] cgroup/cpuset: Show invalid partition reason string Waiman Long
2021-12-05 18:32 ` [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-12-13 21:00   ` Tejun Heo
2021-12-15 14:44     ` Michal Koutný
2021-12-15 18:16       ` Waiman Long
2021-12-15 18:35         ` Tejun Heo
2021-12-15 18:55           ` Waiman Long [this message]
2022-01-12 21:21             ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 7/7] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
2021-12-09 15:39 ` [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long

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