Re: [PATCH 7/7] mm: compaction: add compaction to zone_reclaim_mode

[Andrea Arcangeli <aarcange@redhat.com>]

On Fri, Jul 12, 2013 at 06:57:25PM -0500, Hush Bensen wrote:
> Target reclaim will be done once under low wmark in vanilla kernel,
> however, your patch change it to min wmark, why this behavior change?

This was connected to the previous question, so I tried to answer this
as well in the context of the previous email.

> > +			if (!order)
> > +				goto this_zone_full;
> > +			else
> 
> You do the works should be done in slow path, is it worth?

Not sure to understand the question sorry. The reason for checking
order is that I was skeptical in marking the zone as full, just
because an high order allocation failed. The problem is that if the
cache says "full" and it was just a jitter (like compaction not having
run) , we'll fallback into the other nodes.

In the previous patches however I made compaction a lot more reliable
(no more random skips where compaction isn't even tried for a while
after the cursor meets for example) so maybe I could still mark the
zone full without noticeable effects. The above code has changed in
the meanwhile as I moved the code elsewhere,, so it's better to wait I
send out the new version before reviewing the above further.

Thanks!
Andrea

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