linux-kernel - Re: [PATCH v2 2/4] sched:Consider imbalance_pct when comparing loads in numa_has

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Message-ID: <5588B3E9.2000906@redhat.com>
Date:	Mon, 22 Jun 2015 21:18:33 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v2 2/4] sched:Consider imbalance_pct when comparing loads
 in numa_has_capacity

On 06/22/2015 12:29 PM, Srikar Dronamraju wrote:
> * Rik van Riel <riel@...hat.com> [2015-06-16 10:39:13]:
> 
>> On 06/16/2015 07:56 AM, Srikar Dronamraju wrote:
>>> This is consistent with all other load balancing instances where we
>>> absorb unfairness upto env->imbalance_pct. Absorbing unfairness upto
>>> env->imbalance_pct allows to pull and retain task to their preferred
>>> nodes.
>>>
>>> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>>
>> How does this work with other workloads, eg.
>> single instance SPECjbb2005, or two SPECjbb2005
>> instances on a four node system?
>>
>> Is the load still balanced evenly between nodes
>> with this patch?
>>
> 
> Yes, I have looked at mpstat logs while running SPECjbb2005 for 1JVMper
> System, 2 JVMs per System and 4 JVMs per System and observed that the
> load spreading was similar with and without this patch.
> 
> Also I have visualized using htop when running 0.5X (i.e 48 threads on
> 96 cpu system) cpu stress workloads to see that the spread is similar
> before and after the patch.
> 
> Please let me know if there are any better ways to observe the
> spread. In a slightly loaded or less loaded system, the chance of
> migrating threads to their home node by way of calling migrate_task_to
> and migrate_swap might be curtailed without this patch. i.e 2 process
> each having N/2 threads may converge slower without this change.

Awesome.  Feel free to put my Acked-by: on this patch.

Acked-by: Rik van Riel <riel@...hat.com>


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