Re: [PATCH 0/4] Convert khugepaged to a task_work function

From: Alex Thorlton
Date: Mon Nov 17 2014 - 16:34:00 EST

On Fri, Oct 31, 2014 at 09:27:16PM +0100, Vlastimil Babka wrote:
> What could help would be to cache one or few free huge pages per
> zone with cache
> re-fill done asynchronously, e.g. via work queues. The cache could
> benefit fault-THP
> allocations as well. And adding some logic that if nobody uses the
> cached pages and
> memory is low, then free them. And importantly, if it's not possible
> to allocate huge
> pages for the cache, then prevent scanning for collapse candidates
> as there's no point.
> (well this is probably more complex if some nodes can allocate huge
> pages and others
> not).

I think this would be a pretty cool addition, even separately from this
effort. If we keep a page cached on each NUMA node, then we could,
theoretically, really speed up the khugepaged scans (even if we don't
move those scans to task_work), and regular THP faults. I'll add it to
my ever-growing wish list :)

- Alex
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