From: Mel Gorman <mel@csn.ul.ie>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, Nick Piggin <npiggin@suse.de>,
Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>,
Chris Mason <chris.mason@oracle.com>,
Jens Axboe <jens.axboe@oracle.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure
Date: Fri, 12 Mar 2010 09:09:56 +0000 [thread overview]
Message-ID: <20100312090956.GA18274@csn.ul.ie> (raw)
In-Reply-To: <20100311154124.e1e23900.akpm@linux-foundation.org>
On Thu, Mar 11, 2010 at 03:41:24PM -0800, Andrew Morton wrote:
> On Mon, 8 Mar 2010 11:48:20 +0000
> Mel Gorman <mel@csn.ul.ie> wrote:
>
> > Under memory pressure, the page allocator and kswapd can go to sleep using
> > congestion_wait(). In two of these cases, it may not be the appropriate
> > action as congestion may not be the problem.
>
> clear_bdi_congested() is called each time a write completes and the
> queue is below the congestion threshold.
>
Where you appear to get a kicking is if you want on "congestion" but no
writes are involved. In that case you potentially sleep for the whole timeout
waiting on an event that is not going to occur.
> So if the page allocator or kswapd call congestion_wait() against a
> non-congested queue, they'll wake up on the very next write completion.
>
> Hence the above-quoted claim seems to me to be a significant mis-analysis and
> perhaps explains why the patchset didn't seem to help anything?
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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prev parent reply other threads:[~2010-03-12 9:10 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-08 11:48 [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure Mel Gorman
2010-03-08 11:48 ` [PATCH 1/3] page-allocator: Under memory pressure, wait on pressure to relieve instead of congestion Mel Gorman
2010-03-09 13:35 ` Nick Piggin
2010-03-09 14:17 ` Mel Gorman
2010-03-09 15:03 ` Nick Piggin
2010-03-09 15:42 ` Christian Ehrhardt
2010-03-09 18:22 ` Mel Gorman
2010-03-10 2:38 ` Nick Piggin
2010-03-09 17:35 ` Mel Gorman
2010-03-10 2:35 ` Nick Piggin
2010-03-09 15:50 ` Christoph Lameter
2010-03-09 15:56 ` Christian Ehrhardt
2010-03-09 16:09 ` Christoph Lameter
2010-03-09 17:01 ` Mel Gorman
2010-03-09 17:11 ` Christoph Lameter
2010-03-09 17:30 ` Mel Gorman
2010-03-08 11:48 ` [PATCH 2/3] page-allocator: Check zone pressure when batch of pages are freed Mel Gorman
2010-03-09 9:53 ` Nick Piggin
2010-03-09 10:08 ` Mel Gorman
2010-03-09 10:23 ` Nick Piggin
2010-03-09 10:36 ` Mel Gorman
2010-03-09 11:11 ` Nick Piggin
2010-03-09 11:29 ` Mel Gorman
2010-03-08 11:48 ` [PATCH 3/3] vmscan: Put kswapd to sleep on its own waitqueue, not congestion Mel Gorman
2010-03-09 10:00 ` Nick Piggin
2010-03-09 10:21 ` Mel Gorman
2010-03-09 10:32 ` Nick Piggin
2010-03-11 23:41 ` [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure Andrew Morton
2010-03-12 6:39 ` Christian Ehrhardt
2010-03-12 7:05 ` Andrew Morton
2010-03-12 10:47 ` Mel Gorman
2010-03-12 12:15 ` Christian Ehrhardt
2010-03-12 14:37 ` Andrew Morton
2010-03-15 12:29 ` Mel Gorman
2010-03-15 14:45 ` Christian Ehrhardt
2010-03-15 12:34 ` Christian Ehrhardt
2010-03-15 20:09 ` Andrew Morton
2010-03-16 10:11 ` Mel Gorman
2010-03-18 17:42 ` Mel Gorman
2010-03-22 23:50 ` Mel Gorman
2010-03-23 14:35 ` Christian Ehrhardt
2010-03-23 21:35 ` Corrado Zoccolo
2010-03-24 11:48 ` Mel Gorman
2010-03-24 12:56 ` Corrado Zoccolo
2010-03-23 22:29 ` Rik van Riel
2010-03-24 14:50 ` Mel Gorman
2010-04-19 12:22 ` Christian Ehrhardt
2010-04-19 21:44 ` Johannes Weiner
2010-04-20 7:20 ` Christian Ehrhardt
2010-04-20 8:54 ` Christian Ehrhardt
2010-04-20 15:32 ` Johannes Weiner
2010-04-20 17:22 ` Rik van Riel
2010-04-21 4:23 ` Christian Ehrhardt
2010-04-21 7:35 ` Christian Ehrhardt
2010-04-21 13:19 ` Rik van Riel
2010-04-22 6:21 ` Christian Ehrhardt
2010-04-26 10:59 ` Subject: [PATCH][RFC] mm: make working set portion that is protected tunable v2 Christian Ehrhardt
2010-04-26 11:59 ` KOSAKI Motohiro
2010-04-26 12:43 ` Christian Ehrhardt
2010-04-26 14:20 ` Rik van Riel
2010-04-27 14:00 ` Christian Ehrhardt
2010-04-21 9:03 ` [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure Johannes Weiner
2010-04-21 13:20 ` Rik van Riel
2010-04-20 14:40 ` Rik van Riel
2010-03-24 2:38 ` Greg KH
2010-03-24 11:49 ` Mel Gorman
2010-03-24 13:13 ` Johannes Weiner
2010-03-12 9:09 ` Mel Gorman [this message]
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