linux-kernel - Re: [Resend patch v8 0/13] use runnable load in schedule balance

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Date:	Mon, 24 Jun 2013 03:40:47 -0700
From:	Paul Turner <pjt@...gle.com>
To:	Alex Shi <alex.shi@...el.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	gregkh@...uxfoundation.org,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>, len.brown@...el.com,
	rafael.j.wysocki@...el.com, jkosina@...e.cz,
	Clark Williams <clark.williams@...il.com>, tony.luck@...el.com,
	keescook@...omium.org, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [Resend patch v8 0/13] use runnable load in schedule balance

On Sun, Jun 23, 2013 at 8:15 PM, Alex Shi <alex.shi@...el.com> wrote:
> On 06/20/2013 10:18 AM, Alex Shi wrote:
>> Resend patchset for more convenient pick up.
>> This patch set combine 'use runnable load in balance' serials and 'change
>> 64bit variables to long type' serials. also collected Reviewed-bys, and
>> Tested-bys.
>>
>> The only changed code is fixing load to load_avg convert in UP mode, which
>> found by PeterZ in task_h_load().
>>
>> Paul still has some concern of blocked_load_avg out of balance consideration.
>> but I didn't see the blocked_load_avg usage was thought through now, or some
>> strong reason to make it into balance.
>> So, according to benchmarks testing result I keep patches unchanged.
>
> Ingo & Peter,
>
> This patchset was discussed spread and deeply.
>
> Now just 6th/8th patch has some arguments on them, Paul think it is
> better to consider blocked_load_avg in balance, since it is helpful on
> some scenarios, but I think on most of scenarios, the blocked_load_avg
> just cause load imbalance among cpus. and plus testing show with
> blocked_load_avg the performance is just worse on some benchmarks. So, I
> still prefer to keep it out of balance.

I think you have perhaps misunderstood what I was trying to explain.

I have no problems with not including blocked load in load-balance, in
fact, I encouraged not accumulating it in an average of averages in
CPU load.

The problem is that your current approach has removed it both from
load-balance _and_ from shares distribution; isolation matters as much
as performance in the cgroup case (otherwise you would just not use
cgroups).  I would expect the latter to have quite negative effects on
fairness, this is my primary concern.

>
> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg455196.html
>
> Is it the time to do the decision or give more comments? Thanks!
>>
>> Regards
>> Alex
>>
>> [Resend patch v8 01/13] Revert "sched: Introduce temporary
>> [Resend patch v8 02/13] sched: move few runnable tg variables into
>> [Resend patch v8 03/13] sched: set initial value of runnable avg for
>> [Resend patch v8 04/13] sched: fix slept time double counting in
>> [Resend patch v8 05/13] sched: update cpu load after task_tick.
>> [Resend patch v8 06/13] sched: compute runnable load avg in cpu_load
>> [Resend patch v8 07/13] sched: consider runnable load average in
>> [Resend patch v8 08/13] sched/tg: remove blocked_load_avg in balance
>> [Resend patch v8 09/13] sched: change cfs_rq load avg to unsigned
>> [Resend patch v8 10/13] sched/tg: use 'unsigned long' for load
>> [Resend patch v8 11/13] sched/cfs_rq: change atomic64_t removed_load
>> [Resend patch v8 12/13] sched/tg: remove tg.load_weight
>> [Resend patch v8 13/13] sched: get_rq_runnable_load() can be static
>>
>
>
> --
> Thanks
>     Alex
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