Re: [PATCH 1/11] Add __GFP_MOVABLE flag and update callers

From: Christoph Lameter
Date: Fri Nov 24 2006 - 13:00:04 EST


On Thu, 23 Nov 2006, Linus Torvalds wrote:

> And the assumption would be that if it's MOVABLE, then it's obviously a
> USER allocation (it it can fail much more eagerly - that's really what the
> whole USER bit ends up meaning internally).

We can probably make several types of kernel allocations movable if there
would be some benefit from it.

Mel already has a problem with mlocked user pages in the movable section.
If this is fixed by using page migration to move the mlocked pages then we
can likely make addititional classes kernel pages also movable and reduce
the amount of memory that is unmovable. If we have more movable pages then
the defrag can work more efficiently. Having most pages movable will also
help to make memory unplug a reality.

So please do not require movable pages to be user allocations.
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