linux-kernel - Re: [PATCH 6/6] numa,sched: normalize faults

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Message-ID: <52D97ACD.10209@redhat.com>
Date:	Fri, 17 Jan 2014 13:47:41 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
	mingo@...hat.com, chegu_vinod@...com, mgorman@...e.de,
	Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 6/6] numa,sched: normalize faults_from stats and weigh
 by CPU use

On 01/17/2014 10:04 AM, Peter Zijlstra wrote:
> On Fri, Jan 17, 2014 at 09:51:44AM -0500, Rik van Riel wrote:
>> On 01/17/2014 04:54 AM, Peter Zijlstra wrote:
>>> On Fri, Jan 17, 2014 at 01:17:36AM -0500, riel@...hat.com wrote:
>>>> +			/*
>>>> +			 * Normalize the faults_from, so all tasks in a group
>>>> +			 * count according to CPU use, instead of by the raw
>>>> +			 * number of faults. This prevents the situation where
>>>> +			 * the garbage collector totally dominates the stats,
>>>> +			 * and the access patterns of the worker threads are
>>>> +			 * ignored.
>>>> +			 */
>>>
>>> Instead of focusing on the one example (GC) here, I would suggest
>>> saying something along the lines of: Tasks with little runtime have
>>> little over-all impact on throughput and thus their faults are less
>>> important.
>>
>> Thanks for the review, I have updated the comment
>> accordingly.
>>
>> Does anybody else have comments on this series, or should
>> I start begging for Acked-by: and Reviewed-by: lines? :)
> 
> I still need to get me head around part of the previous patches, and I
> suppose Mel might have a look, give it a few days ;-)

Well, you didn't spot the divide by zero that Vinod somehow
managed to trigger :)

I am also going to add another patch, that prevents the temporary
values from "p->numa_faults[i] >>= 1;" becoming visible, by using
local variables for those calculations.

Expect a v2 soonish.

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