Re: [PATCH v5 07/14] mm, compaction: khugepaged should not give up due to need_resched()

From: David Rientjes
Date: Tue Jul 29 2014 - 05:16:44 EST

On Tue, 29 Jul 2014, Joonsoo Kim wrote:

> Hmm, if thp faults want to pay cost as least as possible, how about
> making thp faults skip async/sync compaction at all?

You can certainly do that with /sys/kernel/mm/transparent_hugepage/defrag.

Without doing memory compaction, though, at least one of my customers will
have their thp ratio drop significantly and for the vast majority of our
machines minimal compaction is all that is needed to allocate a hugepage.
I'm concerned primarily about the straggler that has very lengthy fault
times for even single hugepages.

This patchset will address some of those concerns, but I agree with you
that we should be terminating async compaction with another heuristic
rather than need_resched().
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