From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: linux-mm@kvack.org, Nick Piggin <npiggin@suse.de>,
Johannes Weiner <hannes@cmpxchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake
Date: Mon, 16 Aug 2010 10:47:54 -0400 [thread overview]
Message-ID: <4C694F9A.3030106@redhat.com> (raw)
In-Reply-To: <20100816094350.GH19797@csn.ul.ie>
On 08/16/2010 05:43 AM, Mel Gorman wrote:
> On Mon, Aug 16, 2010 at 10:42:12AM +0100, Mel Gorman wrote:
>> Ordinarily watermark checks are made based on the vmstat NR_FREE_PAGES as
>> it is cheaper than scanning a number of lists. To avoid synchronization
>> overhead, counter deltas are maintained on a per-cpu basis and drained both
>> periodically and when the delta is above a threshold. On large CPU systems,
>> the difference between the estimated and real value of NR_FREE_PAGES can be
>> very high. If the system is under both load and low memory, it's possible
>> for watermarks to be breached. In extreme cases, the number of free pages
>> can drop to 0 leading to the possibility of system livelock.
>>
>> This patch introduces zone_nr_free_pages() to take a slightly more accurate
>> estimate of NR_FREE_PAGES while kswapd is awake. The estimate is not perfect
>> and may result in cache line bounces but is expected to be lighter than the
>> IPI calls necessary to continually drain the per-cpu counters while kswapd
>> is awake.
>>
>> Signed-off-by: Mel Gorman<mel@csn.ul.ie>
>
> And the second I sent this, I realised I had sent a slightly old version
> that missed a compile-fix :(
Acked-by: Rik van Riel <riel@redhat.com>
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next prev parent reply other threads:[~2010-08-16 14:48 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-16 9:42 [RFC PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator Mel Gorman
2010-08-16 9:42 ` [PATCH 1/3] mm: page allocator: Update free page counters after pages are placed on the free list Mel Gorman
2010-08-16 14:04 ` Rik van Riel
2010-08-16 15:26 ` Johannes Weiner
2010-08-17 2:21 ` Minchan Kim
2010-08-17 9:59 ` Mel Gorman
2010-08-17 14:25 ` Minchan Kim
2010-08-18 2:21 ` KAMEZAWA Hiroyuki
2010-08-16 9:42 ` [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Mel Gorman
2010-08-16 9:43 ` Mel Gorman
2010-08-16 14:47 ` Rik van Riel [this message]
2010-08-16 16:06 ` Johannes Weiner
2010-08-17 2:26 ` Minchan Kim
2010-08-17 10:42 ` Mel Gorman
2010-08-17 15:01 ` Minchan Kim
2010-08-17 15:05 ` Mel Gorman
2010-08-17 10:16 ` Mel Gorman
2010-08-17 11:05 ` Johannes Weiner
2010-08-17 14:20 ` Minchan Kim
2010-08-18 8:51 ` Mel Gorman
2010-08-18 14:57 ` Minchan Kim
2010-08-19 8:06 ` Mel Gorman
2010-08-19 10:33 ` Minchan Kim
2010-08-19 10:38 ` Mel Gorman
2010-08-19 14:01 ` Minchan Kim
2010-08-19 14:09 ` Mel Gorman
2010-08-19 14:34 ` Minchan Kim
2010-08-19 15:07 ` Mel Gorman
2010-08-19 15:22 ` Minchan Kim
2010-08-19 15:40 ` Mel Gorman
2010-08-19 15:44 ` Minchan Kim
2010-08-19 15:46 ` Minchan Kim
2010-08-19 16:06 ` Mel Gorman
2010-08-19 16:45 ` Minchan Kim
2010-08-18 2:59 ` KAMEZAWA Hiroyuki
2010-08-18 15:55 ` Christoph Lameter
2010-08-19 0:07 ` KAMEZAWA Hiroyuki
2010-08-19 19:00 ` Christoph Lameter
2010-08-19 23:49 ` KAMEZAWA Hiroyuki
2010-08-20 0:22 ` [PATCH] vmstat : update zone stat threshold at onlining a cpu KAMEZAWA Hiroyuki
2010-08-20 14:54 ` Christoph Lameter
2010-08-20 17:29 ` Andrew Morton
2010-08-23 7:18 ` Mel Gorman
2010-08-16 9:42 ` [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails Mel Gorman
2010-08-16 14:50 ` Rik van Riel
2010-08-17 2:57 ` Minchan Kim
2010-08-18 3:02 ` KAMEZAWA Hiroyuki
2010-08-19 14:47 ` Minchan Kim
2010-08-19 15:10 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-08-23 8:00 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V2 Mel Gorman
2010-08-23 8:00 ` [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Mel Gorman
2010-08-23 12:56 ` Christoph Lameter
2010-08-23 13:03 ` Mel Gorman
2010-08-23 13:41 ` Christoph Lameter
2010-08-23 13:55 ` Mel Gorman
2010-08-23 16:04 ` Christoph Lameter
2010-08-23 16:13 ` Mel Gorman
2010-08-31 17:37 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V3 Mel Gorman
2010-08-31 17:37 ` [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Mel Gorman
2010-08-31 18:20 ` Christoph Lameter
2010-08-31 23:37 ` KOSAKI Motohiro
2010-09-01 7:24 ` Mel Gorman
2010-09-01 7:33 ` KOSAKI Motohiro
2010-09-01 20:16 ` Christoph Lameter
2010-09-01 20:34 ` Mel Gorman
2010-09-02 0:24 ` Christoph Lameter
2010-09-02 0:26 ` KOSAKI Motohiro
2010-09-02 0:39 ` Christoph Lameter
2010-09-02 0:54 ` Christoph Lameter
2010-09-02 0:43 ` Christoph Lameter
2010-09-02 0:49 ` KOSAKI Motohiro
2010-09-02 8:51 ` Mel Gorman
2010-09-03 9:08 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V4 Mel Gorman
2010-09-03 9:08 ` [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Mel Gorman
2010-09-03 22:55 ` Andrew Morton
2010-09-03 23:17 ` Christoph Lameter
2010-09-03 23:28 ` Andrew Morton
2010-09-04 0:54 ` Christoph Lameter
2010-09-05 18:12 ` Mel Gorman
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