linux-kernel - Re: [PATCH v2 1/2] sched/rt: Check to push the task when changing its affinity

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Date:	Sun, 8 Feb 2015 23:19:27 +0800
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Xunlei Pang <xlpang@....com>, lkml <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH v2 1/2] sched/rt: Check to push the task when changing its affinity

On 8 February 2015 at 22:55, Xunlei Pang <pang.xunlei@...aro.org> wrote:
> Hi Steve,
>
> On 7 February 2015 at 05:09, Steven Rostedt <rostedt@...dmis.org> wrote:
>> On Thu,  5 Feb 2015 23:59:33 +0800
>>
>>         if (task_running(rq, p)) {
>>                 if (cpumask_test_cpu() && cpupri_find()) {
>>                 }
>>         } else {
>>                 direct push = 1
>>
>> Also, is the copy of cpus_allowed only done so that cpupri_find is
>> called? If so maybe move it in there too:
>>
>>         if (task_running(rq, p)) {
>>                 if (!cpumask_test_cpu())
>>                         goto update;
>>
>>                 cpumask_copy(&p->cpus_allowed, new_mask);
>>                 p->nr_cpus_allowed = new_weight;
>>
>>                 if (!cpupri_find())
>>                         goto update;
>>
>>                 [...]
>>
>> This way we avoid the double copy of cpumask unless we truly need to do
>> it.
>
> The new_mask can also be used by direct_push case, so I think it's ok.

I guess you mean to avoid the copy if cpumask_test_cpu() is false.
I think this function is not the hot path, making this will make the code
indents too many times or not so good to look, a little awful.

Thanks,
Xunlei
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