Re: [PATCH] mm, thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings

From: Vlastimil Babka
Date: Tue Sep 11 2018 - 04:51:19 EST


On 09/10/2018 10:08 PM, David Rientjes wrote:
> When Andrea brought this up, I suggested that the full solution would be a
> MPOL_F_HUGEPAGE flag that could define thp allocation policy -- the added

Can you elaborate on the semantics of this? You mean that a given vma
could now have two mempolicies, where one would be for hugepages only?
That's likely much more easy to suggest than to implement, with all uapi
consequences...

> benefit is that we could replace the thp "defrag" mode default by setting
> this as part of default_policy. Right now, MADV_HUGEPAGE users are
> concerned about (1) getting thp when system-wide it is not default and (2)
> additional fault latency when direct compaction is not default. They are
> not anticipating the degradation of remote access latency, so overloading
> the meaning of the mode is probably not a good idea.
>