lkml.org 
[lkml]   [2009]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: CFQ is worse than other IO schedulers in some cases
Mike Galbraith said:
> On Wed, 2009-02-18 at 14:00 +0800, Shan Wei wrote:
>
>> In sysbench(version:sysbench-0.4.10), I confirmed followings.
>> - CFQ's performance is worse than other IO schedulers when only multiple
>> threads test.
>> (There is no difference under single thread test.)
>> - It is worse than other IO scheduler when
>> I used read mode. (No regression in write mode).
>> - There is no difference among other IO schedulers. (e.g noop deadline)
>>
>>
>> The Test Result(sysbench):
>> UNIT:Mb/sec
>> __________________________________________________
>> | IO | thread number |
>> | scheduler |-----------------------------------|
>> | | 1 | 3 | 5 | 7 | 9 |
>> +------------|------|-------|------|------|------|
>> |cfq | 77.8 | 32.4 | 43.3 | 55.8 | 58.5 |
>> |noop | 78.2 | 79.0 | 78.2 | 77.2 | 77.0 |
>> |anticipatory| 78.2 | 78.6 | 78.4 | 77.8 | 78.1 |
>> |deadline | 76.9 | 78.4 | 77.0 | 78.4 | 77.9 |
>> +------------------------------------------------+
> 
> My Q6600 box agrees that cfq produces less throughput doing this test,
> but throughput here is ~flat. Disk is external SATA ST3500820AS.
> _________________________________________________
> | IO | thread number |
> | scheduler |----------------------------------|
> | | 1 | 3 | 5 | 7 | 9 |
> +------------|------|------|------|------|------|
> |cfq | 84.4 | 89.1 | 91.3 | 88.8 | 88.8 |
> |noop |102.9 | 99.3 | 99.4 | 99.7 | 98.7 |
> |anticipatory|100.5 |100.1 | 99.8 | 99.7 | 99.6 |
> |deadline | 97.9 | 98.7 | 99.5 | 99.5 | 99.3 |
> +-----------------------------------------------+
>

Thans for you reply.

My box is X5260, I just test it again setting the number of thread with 1 and 5.
The regression is still present.

The test result:
________________________________
| IO | thread number |
| scheduler |------------------
| | 1 | 5 |
+------------|--------|--------|
|cfq | 73.584 | 48.042 |
|noop | 73.653 | 74.055 |
|anticipatory| 73.63 | 72.033 |
|deadline | 73.769 | 72.819 |
+-------------------------------
lspci shows:
[root@NUT io-test]# lspci -nn
00:1f.2 IDE interface [0101]: Intel Corporation 631xESB/632xESB/3100 Chipset SATA IDE Controller [8086:2680] (rev 09)
03:00.0 SCSI storage controller [0100]: LSI Logic / Symbios Logic SAS1064ET PCI-Express Fusion-MPT SAS [1000:0056] (rev 04)

Can you confirm the dump command on your box?

Thanks
Shan Wei

>> Steps to reproduce(sysbench):
>>
>> (1)#echo cfq > /sys/block/sda/queue/scheduler
>>
>> (2)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd prepare
>>
>> (3)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd run
>> [snip]
>> Operations performed: 655360 Read, 0 Write, 0 Other = 655360 Total
>> Read 10Gb Written 0b Total transferred 10Gb (77.835Mb/sec)
>> 4981.44 Requests/sec executed ~~~~~~~~~~~
>> (4)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd cleanup
>>
>> (5)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd prepare
>> (6)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd run
>> [snip]
>> Operations performed: 655360 Read, 0 Write, 0 Other = 655360 Total
>> Read 10Gb Written 0b Total transferred 10Gb (43.396Mb/sec)
>> 2777.35 Requests/sec executed ~~~~~~~~~~~~
>> (7)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd cleanup
>>
>> when doing step 2 or 5, sysbench creats 128 files, and 80M each one.
>> when doing step 4 or 7, sysbench deletes the files.
>> when doing step 3 or 6, thread reads these files continuously and
>> reads file-block-size(default:16Kbyte) at once, just like :
>>
>> t_0 t_0 t_0 t_0 t_0 t_0 t_0
>> ^ ^ ^ ^ ^ ^ ^
>> ---|-----|-----|-----|-----|-----|-----|--------
>> file | 16k | 16k | 16k | 16k | 16k | 16k | 16k | ...
>> ------------------------------------------------
>> (num-threads=1)
>>
>> (t_0 stand for the first thread)
>>
>> t_0 t_1 t_2 t_3 t_4 t_0 t_1
>> ^ ^ ^ ^ ^ ^ ^
>> ---|-----|-----|-----|-----|-----|-----|--------
>> file | 16k | 16k | 16k | 16k | 16k | 16k | 16k | ...
>> ------------------------------------------------
>> (num-threads=5)
>>
>> (the executed threads are decide by the thread scheduler)
>>
>>
>> The Hardware Infos:
>> Arch :x86_64
>> CPU :4cpu; GenuineIntel 3325.087 MHz
>> MEMORY :4044128kB
>>
>> ----
>> Shan Wei
>>
--
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: 2009-02-18 12:23    [from the cache]
©2003-2011 Jasper Spaans