linux-kernel - Re: [RFC PATCH 3/3] sched/fair: Use different cachelines for readers and writers of load

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Date:	Mon, 30 Nov 2015 22:55:02 -0500
From:	Waiman Long <waiman.long@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>,
	Paul Turner <pjt@...gle.com>, Ben Segall <bsegall@...gle.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Yuyang Du <yuyang.du@...el.com>
Subject: Re: [RFC PATCH 3/3] sched/fair: Use different cachelines for readers
 and writers of load_avg

On 11/30/2015 05:09 PM, Peter Zijlstra wrote:
> On Mon, Nov 30, 2015 at 02:13:32PM -0500, Waiman Long wrote:
>>> This begs the question tough; why are you running a global load in a
>>> cgroup; and do we really need to update this for the root cgroup? It
>>> seems to me we don't need calc_tg_weight() for the root cgroup, it
>>> doesn't need to normalize its weight numbers.
>>>
>>> That is; isn't this simply a problem we should avoid?
>> I didn't use any cgroup in my test setup. Autogroup was enabled, though.
>> Booting up a 4.4-rc2 kernel caused sched_create_group() to be called 56
>> times.
> Yeah, can you kill autogroup and see if that helps? If not, we probably
> should add some code to avoid calculating things for the root group.

I will try that out tomorrow. However, SCHED_AUTOGROUP was enabled in 
the distribution kernels. So we still need to look at that with 
autogroup enabled.

Cheers,
Longman
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