Re: [PATCH] sched: wake-affine throttle

From: Michael Wang
Date: Thu Apr 11 2013 - 05:02:56 EST


On 04/11/2013 04:44 PM, Mike Galbraith wrote:
> On Thu, 2013-04-11 at 16:26 +0800, Michael Wang wrote:
>
>> The 1:N is a good reason to explain why the chance that wakee's hot data
>> cached on curr_cpu is lower, and since it's just 'lower' not 'extinct',
>> after the throttle interval large enough, it will be balanced, this
>> could be proved, since during my test, when the interval become too big,
>> the improvement start to drop.
>
> Magnitude of improvement drops just because there's less damage done
> methinks. You'll eventually run out of measurable damage :)
>
> Yes, it's not really extinct, you _can_ reap a gain, it's just not at
> all likely to work out. A more symetric load will fare better, but any
> 1:N thing just has to spread far and wide to have any chance to perform.

Agree.

>> Hmm...that's an interesting point, the workload contain different
>> 'priority' works, and depend on each other, if mother starving, all the
>> kids could do nothing but wait for her, may be that's the reason why the
>> benefit is so significant, since in such case, mother's little quicker
>> respond will make all the kids happy :)
>
> Exactly. The entire load is server latency bound. Keep the server on
> cpu, the load performs as best it can given unavoidable data miss cost.

Nice point :)

Regards,
Michael Wang

>
> -Mike
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/