Re: [PATCH 24/27] mm, page_alloc: Remove fair zone allocation policy

Mel Gorman
2016-06-17T12:07:10Z

On Fri, Jun 17, 2016 at 01:27:09PM +0200, Vlastimil Babka wrote:
> On 06/09/2016 08:04 PM, Mel Gorman wrote:
> >The fair zone allocation policy interleaves allocation requests between
> >zones to avoid an age inversion problem whereby new pages are reclaimed
> >to balance a zone. Reclaim is now node-based so this should no longer be
> >an issue and the fair zone allocation policy is not free. This patch
> >removes it.
>
> I wonder if fair zone allocation had the side effect of preventing e.g. a
> small Normal zone to be almost fully occupied by long-lived unreclaimable
> allocations early in the kernel lifetime. So that might be one thing to
> watch out for.

It's a marginal corner case and the zonelist scan is slightly inefficient
as the first zone is always skipped but the impact is light.

> But otherwise I would agree it should be no longer needed
> with node-based reclaim.
>
> >Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>

Thanks.

--
Mel Gorman
SUSE Labs