Re: [PATCH v8] mm: make lru_add_drain_all() selective

[Chris Metcalf]

On 8/14/2013 5:12 PM, Andrew Morton wrote:
> On Wed, 14 Aug 2013 16:22:18 -0400 Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote:
>
>> This change makes lru_add_drain_all() only selectively interrupt
>> the cpus that have per-cpu free pages that can be drained.
>>
>> This is important in nohz mode where calling mlockall(), for
>> example, otherwise will interrupt every core unnecessarily.
> Changelog isn't very informative.  I added this:
>
> : This is important on workloads where nohz cores are handling 10 Gb traffic
> : in userspace.  Those CPUs do not enter the kernel and place pages into LRU
> : pagevecs and they really, really don't want to be interrupted, or they
> : drop packets on the floor.
>
> to attempt to describe the rationale for the patch.

Thanks.  More motivational text is always a good thing.

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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