Mel Gorman wrote:
On Fri, Mar 12, 2010 at 02:05:26AM -0500, Andrew Morton wrote:
On Fri, 12 Mar 2010 07:39:26 +0100 Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx> wrote:
Andrew Morton wrote:
On Mon, 8 Mar 2010 11:48:20 +0000
Mel Gorman <mel@xxxxxxxxx> wrote:
[...]
If not, we broke it again.
We were broken with respect to this in the first place. That
cond_reched() is badly placed and waiting on congestion when congestion
might not be involved is also a bit odd.
It's possible that Christian's specific problem would also be addressed
by the following patch. Christian, willing to test?
Will is here, but no chance before monday/tuesday to get a free machine
slot - I'll post results as soon as I get them.
It still feels a bit unnatural though that the page allocator waits on
congestion when what it really cares about is watermarks. Even if this
patch works for Christian, I think it still has merit so will kick it a
few more times.
In whatever way I can look at it watermark_wait should be supperior to
congestion_wait. Because as Mel points out waiting for watermarks is
what is semantically correct there.
If there eventually some day comes a solution without any of those waits
I'm fine too - e.g. by closing whatever races we have and fixing that
one context can never run into this in direct_reclaim:
1. free pages with try_to_free
2. not getting one in the subsequent get_page call
But as long as we have a wait - watermark waiting > congestion waiting
(IMHO).
==== CUT HERE ====
page-allocator: Attempt page allocation immediately after direct reclaim
[...]
--
Grüsse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
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