lkml.org 
[lkml]   [2010]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2


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.



--

Grüsse / regards, Christian Ehrhardt
IBM Linux Technology Center, System z Linux Performance
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2010-11-03 11:53    [W:0.114 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site