From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Linux Kernel List <linux-kernel@vger.kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Minchan Kim <minchan.kim@gmail.com>,
Wu Fengguang <fengguang.wu@intel.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2
Date: Wed, 03 Nov 2010 11:50:35 +0100 [thread overview]
Message-ID: <4CD13E7B.5090804@linux.vnet.ibm.com> (raw)
In-Reply-To: <20101018135535.GC30667@csn.ul.ie>
On 10/18/2010 03:55 PM, Mel Gorman wrote:
> On Thu, Oct 14, 2010 at 05:28:33PM +0200, Christian Ehrhardt wrote:
>
>> Seing the patches Mel sent a few weeks ago I realized that this series
>> might be at least partially related to my reports in 1Q 2010 - so I ran my
>> testcase on a few kernels to provide you with some more backing data.
>
> Thanks very much for revisiting this.
>
>> Results are always the average of three iozone runs as it is known to be somewhat noisy - especially when affected by the issue I try to show here.
>> As discussed in detail in older threads the setup uses 16 disks and scales the number of concurrent iozone processes.
>> Processes are evenly distributed so that it always is one process per disk.
>> In the past we reported 40% to 80% degradation for the sequential read case based on 2.6.32 which can still be seen.
>> What we found was that the allocations for page cache with GFP_COLD flag loop a long time between try_to_free, get_page, reclaim as free makes some progress and due to that GFP_COLD allocations can loop and retry.
>> In addition my case had no writes at all, which forced congestion_wait to wait the full timeout all the time.
>>
>> Kernel (git) 4 8 16 deviation #16 case comment
>> linux-2.6.30 902694 1396073 1892624 base base
>> linux-2.6.32 752008 990425 932938 -50.7% impact as reported in 1Q 2010
>> linux-2.6.35 63532 71573 64083 -96.6% got even worse
>> linux-2.6.35.6 176485 174442 212102 -88.8% fixes useful, but still far away
>> linux-2.6.36-rc4-trace 119683 188997 187012 -90.1% still bad
>> linux-2.6.36-rc4-fix 884431 1114073 1470659 -22.3% Mels fixes help a lot!
>>
[...]
> If all goes according to plan,
> kernel 2.6.37-rc1 will be of interest. Thanks again.
Here a measurement with 2.6.37-rc1 as confirmation of progress:
linux-2.6.37-rc1 876588 1161876 1643430 -13.1% even better than 2.6.36-fix
That means 2.6.37-rc1 really shows what we hoped for.
And it eventually even turned out a little bit better than 2.6.36 + your fixes.
--
Grusse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
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next prev parent reply other threads:[~2010-11-03 10:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-15 12:27 [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Mel Gorman
2010-09-15 12:27 ` [PATCH 1/8] tracing, vmscan: Add trace events for LRU list shrinking Mel Gorman
2010-09-15 12:27 ` [PATCH 2/8] writeback: Account for time spent congestion_waited Mel Gorman
2010-09-15 12:27 ` [PATCH 3/8] vmscan: Synchronous lumpy reclaim should not call congestion_wait() Mel Gorman
2010-09-15 12:27 ` [PATCH 4/8] vmscan: Narrow the scenarios lumpy reclaim uses synchrounous reclaim Mel Gorman
2010-09-15 12:27 ` [PATCH 5/8] vmscan: Remove dead code in shrink_inactive_list() Mel Gorman
2010-09-15 12:27 ` [PATCH 6/8] vmscan: isolated_lru_pages() stop neighbour search if neighbour cannot be isolated Mel Gorman
2010-09-15 12:27 ` [PATCH 7/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs Mel Gorman
2010-09-16 7:59 ` Minchan Kim
2010-09-16 8:23 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone Mel Gorman
2010-09-16 8:13 ` Minchan Kim
2010-09-16 9:18 ` Mel Gorman
2010-09-16 14:11 ` Minchan Kim
2010-09-16 15:18 ` Mel Gorman
2010-09-16 22:28 ` Andrew Morton
2010-09-20 9:52 ` Mel Gorman
2010-09-21 21:44 ` Andrew Morton
2010-09-21 22:10 ` Mel Gorman
2010-09-21 22:24 ` Andrew Morton
2010-09-20 13:05 ` [PATCH] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encounted in the current zone fix Mel Gorman
2010-09-16 22:28 ` [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Andrew Morton
2010-09-17 7:52 ` Mel Gorman
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-18 13:55 ` Mel Gorman
2010-10-22 12:29 ` Christian Ehrhardt
2010-11-03 10:50 ` Christian Ehrhardt [this message]
2010-11-10 14:37 ` Mel Gorman
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