Re: [PATCH v4 05/11] mm/migrate: clear __GFP_RECLAIM for THP allocation for migration

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2020년 7월 8일 (수) 오후 4:48, Michal Hocko <mhocko@xxxxxxxxxx>님이 작성:
>
> On Wed 08-07-20 16:19:17, Joonsoo Kim wrote:
> > On Tue, Jul 07, 2020 at 01:40:19PM +0200, Michal Hocko wrote:
> [...]
> > Subject: [PATCH] mm/migrate: clear __GFP_RECLAIM for THP allocation for
> >  migration
> >
> > In migration target allocation functions, THP allocations uses different
> > gfp_mask, especially, in regard to the reclaim gfp_mask. There is no
> > reason to use different reclaim gfp_mask for each cases and it is
> > an obstacle to make a common function in order to clean-up migration
> > target allocation functions. This patch fixes this situation by using
> > common reclaim gfp_mask for THP allocation.
>
> I would find the following more understandable, feel free to reuse parts
> that you like:
> "
> new_page_nodemask is a migration callback and it tries to use a common
> gfp flags for the target page allocation whether it is a base page or a
> THP. The later only adds GFP_TRANSHUGE to the given mask. This results
> in the allocation being slightly more aggressive than necessary because
> the resulting gfp mask will contain also __GFP_RECLAIM_KSWAPD. THP
> allocations usually exclude this flag to reduce over eager background
> reclaim during a high THP allocation load which has been seen during
> large mmaps initialization. There is no indication that this is a
> problem for migration as well but theoretically the same might happen
> when migrating large mappings to a different node. Make the migration
> callback consistent with regular THP allocations.
> "

Looks good!
I will use this description.

Thanks.





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