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From: Mel Gorman <mgorman@suse.de>
To: Rik van Riel <riel@redhat.com>
Cc: Linux-MM <linux-mm@kvack.org>, Minchan Kim <minchan@kernel.org>,
	Jim Schutt <jaschut@sandia.gov>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] mm: have order > 0 compaction start near a pageblock with free pages
Date: Tue, 7 Aug 2012 15:52:33 +0100	[thread overview]
Message-ID: <20120807145233.GG29814@suse.de> (raw)
In-Reply-To: <50212A05.2070503@redhat.com>

On Tue, Aug 07, 2012 at 10:45:25AM -0400, Rik van Riel wrote:
> On 08/07/2012 08:31 AM, Mel Gorman wrote:
> >commit [7db8889a: mm: have order>  0 compaction start off where it left]
> >introduced a caching mechanism to reduce the amount work the free page
> >scanner does in compaction. However, it has a problem. Consider two process
> >simultaneously scanning free pages
> >
> >				    			C
> >Process A		M     S     			F
> >		|---------------------------------------|
> >Process B		M 	FS
> 
> Argh. Good spotting.
> 
> >This is not optimal and it can still race but the compact_cached_free_pfn
> >will be pointing to or very near a pageblock with free pages.
> 
> Agreed on the "not optimal", but I also cannot think of a better
> idea right now. Getting this fixed for 3.6 is important, we can
> think of future optimizations in San Diego.
> 

Sounds like a plan.

> >Signed-off-by: Mel Gorman<mgorman@suse.de>
> 
> Reviewed-by: Rik van Riel <riel@redhat.com>
> 

Thanks very much.

Jim, what are the chances of getting this series tested with your large
data workload? As it's on top of 3.5, it should be less scary than
testing 3.6-rc1 but if you are comfortable testing 3.6-rc1 then please
test with just this patch on top.

-- 
Mel Gorman
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de>
To: Rik van Riel <riel@redhat.com>
Cc: Linux-MM <linux-mm@kvack.org>, Minchan Kim <minchan@kernel.org>,
	Jim Schutt <jaschut@sandia.gov>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] mm: have order > 0 compaction start near a pageblock with free pages
Date: Tue, 7 Aug 2012 15:52:33 +0100	[thread overview]
Message-ID: <20120807145233.GG29814@suse.de> (raw)
In-Reply-To: <50212A05.2070503@redhat.com>

On Tue, Aug 07, 2012 at 10:45:25AM -0400, Rik van Riel wrote:
> On 08/07/2012 08:31 AM, Mel Gorman wrote:
> >commit [7db8889a: mm: have order>  0 compaction start off where it left]
> >introduced a caching mechanism to reduce the amount work the free page
> >scanner does in compaction. However, it has a problem. Consider two process
> >simultaneously scanning free pages
> >
> >				    			C
> >Process A		M     S     			F
> >		|---------------------------------------|
> >Process B		M 	FS
> 
> Argh. Good spotting.
> 
> >This is not optimal and it can still race but the compact_cached_free_pfn
> >will be pointing to or very near a pageblock with free pages.
> 
> Agreed on the "not optimal", but I also cannot think of a better
> idea right now. Getting this fixed for 3.6 is important, we can
> think of future optimizations in San Diego.
> 

Sounds like a plan.

> >Signed-off-by: Mel Gorman<mgorman@suse.de>
> 
> Reviewed-by: Rik van Riel <riel@redhat.com>
> 

Thanks very much.

Jim, what are the chances of getting this series tested with your large
data workload? As it's on top of 3.5, it should be less scary than
testing 3.6-rc1 but if you are comfortable testing 3.6-rc1 then please
test with just this patch on top.

-- 
Mel Gorman
SUSE Labs

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  reply	other threads:[~2012-08-07 14:52 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-07 12:31 [RFC PATCH 0/6] Improve hugepage allocation success rates under load Mel Gorman
2012-08-07 12:31 ` Mel Gorman
2012-08-07 12:31 ` [PATCH 1/6] mm: compaction: Update comment in try_to_compact_pages Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 13:19   ` Rik van Riel
2012-08-07 13:19     ` Rik van Riel
2012-08-07 23:25   ` Minchan Kim
2012-08-07 23:25     ` Minchan Kim
2012-08-07 12:31 ` [PATCH 2/6] mm: vmscan: Scale number of pages reclaimed by reclaim/compaction based on failures Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 13:23   ` Rik van Riel
2012-08-07 13:23     ` Rik van Riel
2012-08-08  1:48   ` Minchan Kim
2012-08-08  1:48     ` Minchan Kim
2012-08-08  7:55     ` Mel Gorman
2012-08-08  7:55       ` Mel Gorman
2012-08-08  8:27       ` Minchan Kim
2012-08-08  8:27         ` Minchan Kim
2012-08-08  8:51         ` Mel Gorman
2012-08-08  8:51           ` Mel Gorman
2012-08-08 23:51           ` Minchan Kim
2012-08-08 23:51             ` Minchan Kim
2012-08-09  7:49             ` Mel Gorman
2012-08-09  7:49               ` Mel Gorman
2012-08-09  8:27               ` Minchan Kim
2012-08-09  8:27                 ` Minchan Kim
2012-08-09  9:20                 ` Mel Gorman
2012-08-09  9:20                   ` Mel Gorman
2012-08-09 20:29                   ` Rik van Riel
2012-08-09 20:29                     ` Rik van Riel
2012-08-10  8:14                     ` Mel Gorman
2012-08-10  8:14                       ` Mel Gorman
2012-08-09 23:27                   ` Minchan Kim
2012-08-09 23:27                     ` Minchan Kim
2012-08-10  8:34                     ` Mel Gorman
2012-08-10  8:34                       ` Mel Gorman
2012-08-10  8:48                       ` Minchan Kim
2012-08-10  8:48                         ` Minchan Kim
2012-08-07 12:31 ` [PATCH 3/6] mm: kswapd: Continue reclaiming for reclaim/compaction if the minimum number of pages have not been reclaimed Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 13:26   ` Rik van Riel
2012-08-07 13:26     ` Rik van Riel
2012-08-08  2:07   ` Minchan Kim
2012-08-08  2:07     ` Minchan Kim
2012-08-08  9:07     ` Mel Gorman
2012-08-08  9:07       ` Mel Gorman
2012-08-08  9:58       ` Mel Gorman
2012-08-08  9:58         ` Mel Gorman
2012-08-07 12:31 ` [PATCH 4/6] mm: compaction: Capture a suitable high-order page immediately when it is made available Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 13:30   ` Rik van Riel
2012-08-07 13:30     ` Rik van Riel
2012-08-07 12:31 ` [PATCH 5/6] mm: have order > 0 compaction start off where it left Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 12:31 ` [PATCH 6/6] mm: have order > 0 compaction start near a pageblock with free pages Mel Gorman
2012-08-07 12:31   ` Mel Gorman
2012-08-07 14:45   ` Rik van Riel
2012-08-07 14:45     ` Rik van Riel
2012-08-07 14:52     ` Mel Gorman [this message]
2012-08-07 14:52       ` Mel Gorman
2012-08-07 15:20       ` Jim Schutt
2012-08-07 15:20         ` Jim Schutt
2012-08-07 15:45         ` Mel Gorman
2012-08-07 15:45           ` Mel Gorman
2012-08-08  4:36   ` Minchan Kim
2012-08-08  4:36     ` Minchan Kim
2012-08-08 10:18     ` Mel Gorman
2012-08-08 10:18       ` Mel Gorman

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