lkml.org 
[lkml]   [2010]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure
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@linux.vnet.ibm.com> wrote:
>>
>>>
>>> Andrew Morton wrote:
>>>> On Mon, 8 Mar 2010 11:48:20 +0000
>>>> Mel Gorman <mel@csn.ul.ie> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2010-03-12 13:17    [W:0.091 / U:1.536 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site