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

[Andrew Morton]

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.
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