From: Mel Gorman <mgorman@suse.de> To: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, James Bottomley <James.Bottomley@hansenpartnership.com>, Colin King <colin.king@canonical.com>, Raghavendra D Prabhu <raghu.prabhu13@gmail.com>, Jan Kara <jack@suse.cz>, Chris Mason <chris.mason@oracle.com>, Pekka Enberg <penberg@kernel.org>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org> Subject: Re: [PATCH 3/4] mm: slub: Do not take expensive steps for SLUBs speculative high-order allocations Date: Tue, 17 May 2011 17:22:56 +0100 [thread overview] Message-ID: <20110517162256.GO5279@suse.de> (raw) In-Reply-To: <alpine.DEB.2.00.1105170847550.11187@router.home> On Tue, May 17, 2011 at 08:51:47AM -0500, Christoph Lameter wrote: > On Tue, 17 May 2011, Mel Gorman wrote: > > > entirely. Christoph wants to maintain historic behaviour of SLUB to > > maximise the number of high-order pages it uses and at the end of the > > day, which option performs better depends entirely on the workload > > and machine configuration. > > That is not what I meant. I would like more higher order allocations to > succeed. That does not mean that slubs allocation methods and flags passed > have to stay the same. You can change the slub behavior if it helps. > In this particular patch, the success rate for high order allocations would likely decrease in low memory conditions albeit the latency when calling the page allocator will be lower and the disruption to the system will be less (no copying or reclaim of pages). My expectation would be that it's cheaper for SLUB to fall back than compact memory or reclaim pages even if this means a slab page is smaller until more memory is free. However, if the "goodness" criteria is high order allocation success rate, the patch shouldn't be merged. > I am just suspicious of compaction. If these mods are needed to reduce the > amount of higher order pages then compaction does not have the > beneficial effect that it should have. It does not actually > increase the available higher order pages. Fix that first. > The problem being addressed was the machine being hung at worst and in other cases having kswapd pinned at 99-100% CPU. It's now been shown that modifying SLUB is not necessary to fix this because the bug was in page reclaim. The high-order allocation success rate didn't come into it. -- Mel Gorman SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de> To: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, James Bottomley <James.Bottomley@hansenpartnership.com>, Colin King <colin.king@canonical.com>, Raghavendra D Prabhu <raghu.prabhu13@gmail.com>, Jan Kara <jack@suse.cz>, Chris Mason <chris.mason@oracle.com>, Pekka Enberg <penberg@kernel.org>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org> Subject: Re: [PATCH 3/4] mm: slub: Do not take expensive steps for SLUBs speculative high-order allocations Date: Tue, 17 May 2011 17:22:56 +0100 [thread overview] Message-ID: <20110517162256.GO5279@suse.de> (raw) In-Reply-To: <alpine.DEB.2.00.1105170847550.11187@router.home> On Tue, May 17, 2011 at 08:51:47AM -0500, Christoph Lameter wrote: > On Tue, 17 May 2011, Mel Gorman wrote: > > > entirely. Christoph wants to maintain historic behaviour of SLUB to > > maximise the number of high-order pages it uses and at the end of the > > day, which option performs better depends entirely on the workload > > and machine configuration. > > That is not what I meant. I would like more higher order allocations to > succeed. That does not mean that slubs allocation methods and flags passed > have to stay the same. You can change the slub behavior if it helps. > In this particular patch, the success rate for high order allocations would likely decrease in low memory conditions albeit the latency when calling the page allocator will be lower and the disruption to the system will be less (no copying or reclaim of pages). My expectation would be that it's cheaper for SLUB to fall back than compact memory or reclaim pages even if this means a slab page is smaller until more memory is free. However, if the "goodness" criteria is high order allocation success rate, the patch shouldn't be merged. > I am just suspicious of compaction. If these mods are needed to reduce the > amount of higher order pages then compaction does not have the > beneficial effect that it should have. It does not actually > increase the available higher order pages. Fix that first. > The problem being addressed was the machine being hung at worst and in other cases having kswapd pinned at 99-100% CPU. It's now been shown that modifying SLUB is not necessary to fix this because the bug was in page reclaim. The high-order allocation success rate didn't come into it. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-05-17 16:23 UTC|newest] Thread overview: 119+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-05-13 14:03 [PATCH 0/4] Reduce impact to overall system of SLUB using high-order allocations V2 Mel Gorman 2011-05-13 14:03 ` Mel Gorman 2011-05-13 14:03 ` [PATCH 1/4] mm: vmscan: Correct use of pgdat_balanced in sleeping_prematurely Mel Gorman 2011-05-13 14:03 ` Mel Gorman 2011-05-13 14:28 ` Johannes Weiner 2011-05-13 14:28 ` Johannes Weiner 2011-05-14 16:30 ` Minchan Kim 2011-05-14 16:30 ` Minchan Kim 2011-05-16 14:30 ` Rik van Riel 2011-05-16 14:30 ` Rik van Riel 2011-05-13 14:03 ` [PATCH 2/4] mm: slub: Do not wake kswapd for SLUBs speculative high-order allocations Mel Gorman 2011-05-13 14:03 ` Mel Gorman 2011-05-16 21:10 ` David Rientjes 2011-05-16 21:10 ` David Rientjes 2011-05-18 6:09 ` Pekka Enberg 2011-05-18 6:09 ` Pekka Enberg 2011-05-18 17:21 ` Christoph Lameter 2011-05-18 17:21 ` Christoph Lameter 2011-05-13 14:03 ` [PATCH 3/4] mm: slub: Do not take expensive steps " Mel Gorman 2011-05-13 14:03 ` Mel Gorman 2011-05-16 21:16 ` David Rientjes 2011-05-16 21:16 ` David Rientjes 2011-05-17 8:42 ` Mel Gorman 2011-05-17 8:42 ` Mel Gorman 2011-05-17 13:51 ` Christoph Lameter 2011-05-17 13:51 ` Christoph Lameter 2011-05-17 16:22 ` Mel Gorman [this message] 2011-05-17 16:22 ` Mel Gorman 2011-05-17 17:52 ` Christoph Lameter 2011-05-17 17:52 ` Christoph Lameter 2011-05-17 19:35 ` David Rientjes 2011-05-17 19:35 ` David Rientjes 2011-05-17 19:31 ` David Rientjes 2011-05-17 19:31 ` David Rientjes 2011-05-13 14:03 ` [PATCH 4/4] mm: vmscan: If kswapd has been running too long, allow it to sleep Mel Gorman 2011-05-13 14:03 ` Mel Gorman 2011-05-15 10:27 ` KOSAKI Motohiro 2011-05-15 10:27 ` KOSAKI Motohiro 2011-05-16 4:21 ` James Bottomley 2011-05-16 4:21 ` James Bottomley 2011-05-16 5:04 ` Minchan Kim 2011-05-16 5:04 ` Minchan Kim 2011-05-16 8:45 ` Mel Gorman 2011-05-16 8:45 ` Mel Gorman 2011-05-16 8:45 ` Mel Gorman 2011-05-16 8:58 ` Minchan Kim 2011-05-16 8:58 ` Minchan Kim 2011-05-16 8:58 ` Minchan Kim 2011-05-16 10:27 ` Mel Gorman 2011-05-16 10:27 ` Mel Gorman 2011-05-16 10:27 ` Mel Gorman 2011-05-16 23:50 ` Minchan Kim 2011-05-16 23:50 ` Minchan Kim 2011-05-17 0:48 ` Minchan Kim 2011-05-17 0:48 ` Minchan Kim 2011-05-17 0:48 ` Minchan Kim 2011-05-17 10:38 ` Mel Gorman 2011-05-17 10:38 ` Mel Gorman 2011-05-17 10:38 ` Mel Gorman 2011-05-17 13:50 ` Colin Ian King 2011-05-17 13:50 ` Colin Ian King 2011-05-17 16:15 ` [PATCH] mm: vmscan: Correctly check if reclaimer should schedule during shrink_slab Mel Gorman 2011-05-17 16:15 ` Mel Gorman 2011-05-18 0:45 ` KOSAKI Motohiro 2011-05-18 0:45 ` KOSAKI Motohiro 2011-05-19 0:03 ` Minchan Kim 2011-05-19 0:03 ` Minchan Kim 2011-05-19 0:03 ` Minchan Kim 2011-05-19 0:09 ` Minchan Kim 2011-05-19 0:09 ` Minchan Kim 2011-05-19 0:09 ` Minchan Kim 2011-05-19 11:36 ` Colin Ian King 2011-05-19 11:36 ` Colin Ian King 2011-05-20 0:06 ` Minchan Kim 2011-05-20 0:06 ` Minchan Kim 2011-05-20 0:06 ` Minchan Kim 2011-05-18 4:19 ` [PATCH 4/4] mm: vmscan: If kswapd has been running too long, allow it to sleep Minchan Kim 2011-05-18 4:19 ` Minchan Kim 2011-05-18 7:39 ` Colin Ian King 2011-05-18 7:39 ` Colin Ian King 2011-05-18 4:09 ` James Bottomley 2011-05-18 4:09 ` James Bottomley 2011-05-18 1:05 ` KOSAKI Motohiro 2011-05-18 1:05 ` KOSAKI Motohiro 2011-05-18 5:44 ` Minchan Kim 2011-05-18 5:44 ` Minchan Kim 2011-05-18 5:44 ` Minchan Kim 2011-05-18 6:05 ` KOSAKI Motohiro 2011-05-18 6:05 ` KOSAKI Motohiro 2011-05-18 9:58 ` Mel Gorman 2011-05-18 9:58 ` Mel Gorman 2011-05-18 9:58 ` Mel Gorman 2011-05-18 22:55 ` Minchan Kim 2011-05-18 22:55 ` Minchan Kim 2011-05-18 23:54 ` KOSAKI Motohiro 2011-05-18 23:54 ` KOSAKI Motohiro 2011-05-18 0:26 ` KOSAKI Motohiro 2011-05-18 0:26 ` KOSAKI Motohiro 2011-05-18 9:57 ` Mel Gorman 2011-05-18 9:57 ` Mel Gorman 2011-05-16 8:45 ` Mel Gorman 2011-05-16 8:45 ` Mel Gorman 2011-05-16 14:30 ` Rik van Riel 2011-05-16 14:30 ` Rik van Riel 2011-05-13 15:19 ` [PATCH 0/4] Reduce impact to overall system of SLUB using high-order allocations V2 James Bottomley 2011-05-13 15:19 ` James Bottomley 2011-05-13 15:19 ` James Bottomley 2011-05-13 15:52 ` Mel Gorman 2011-05-13 15:52 ` Mel Gorman 2011-05-13 15:21 ` Christoph Lameter 2011-05-13 15:21 ` Christoph Lameter 2011-05-13 15:43 ` Mel Gorman 2011-05-13 15:43 ` Mel Gorman 2011-05-14 8:34 ` Colin Ian King 2011-05-14 8:34 ` Colin Ian King 2011-05-16 8:37 ` Mel Gorman 2011-05-16 8:37 ` Mel Gorman 2011-05-16 11:24 ` Colin Ian King 2011-05-16 11:24 ` Colin Ian King
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