linux-kernel - Re: [RFC PATCH v2 09/17] cgroup: Keep accurate count of tasks in each css

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Message-ID: <b0a5ea12-317f-70a3-2efe-e0b7f7673e3e@redhat.com>
Date:   Thu, 18 May 2017 11:56:38 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, kernel-team@...com, pjt@...gle.com,
        luto@...capital.net, efault@....de
Subject: Re: [RFC PATCH v2 09/17] cgroup: Keep accurate count of tasks in each
 css_set

On 05/17/2017 05:40 PM, Tejun Heo wrote:
> Hello,
>
> On Mon, May 15, 2017 at 09:34:08AM -0400, Waiman Long wrote:
>> The reference count in the css_set data structure was used as a
>> proxy of the number of tasks attached to that css_set. However, that
>> count is actually not an accurate measure especially with thread mode
>> support. So a new variable task_count is added to the css_set to keep
>> track of the actual task count. This new variable is protected by
>> the css_set_lock. Functions that require the actual task count are
>> updated to use the new variable.
>>
>> Signed-off-by: Waiman Long <longman@...hat.com>
> Looks good.  We probably should replace css_set_populated() to use
> this too.
>
> Thanks.
>
Yes, you are right. css_set_populated() can be replaced with a check on
the task_count.

Regards,
Longman