Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
significant degrade in random read for block devices using O_DIRECT.
The drop occurs for all block sizes and ranges from 30%-40. CPU usage
is also lower although it may already be so low as to be irrelavent.
tolerance = 0.00 + 3.00% of 2.5.70-mm1
2.5.70-mm1 2.5.70-mm2
Blocksize KBs/sec KBs/sec %diff diff tolerance
---------- ------------ ------------ -------- ------------ ------------
4096 1567 924 -41.03 -643.00 47.01 *
8192 3057 1815 -40.63 -1242.00 91.71 *
16384 5745 3509 -38.92 -2236.00 172.35 *
65536 17357 11283 -34.99 -6074.00 520.71 *
262144 37537 27302 -27.27 -10235.00 1126.11 *
Full results can be found at:
http://www-124.ibm.com/developerworks/oss/linuxperf/regression/2.5.70-mm2/2.5.70-mm1-vs-2.5.70-mm2/
Steve
Steven Pratt wrote:
> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
> significant degrade in random read for block devices using O_DIRECT.
> The drop occurs for all block sizes and ranges from 30%-40. CPU usage
> is also lower although it may already be so low as to be irrelavent.
Hi Steven, this is quite likely to be an io scheduler problem.
Is your test program rawread v2.1.5? What is the command line
you are using to invoke the program?
Nick Piggin wrote:
> Steven Pratt wrote:
>
>> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
>> significant degrade in random read for block devices using
>> O_DIRECT. The drop occurs for all block sizes and ranges from
>> 30%-40. CPU usage is also lower although it may already be so low as
>> to be irrelavent.
>
> Hi Steven, this is quite likely to be an io scheduler problem.
> Is your test program rawread v2.1.5?
This test was actually using 2.1.4, but the only difference in the 2.1.5
version is a fix for the test label array for the aio versions of the
test. No functional change, just fixed the outputed test description.
> What is the command line you are using to invoke the program?
rawread -t6 -p8 -m1 -d2 -s4096 -n65536 -l1 -z -x
Which you can find if you follow either results link and look in the
benchmark directory where all raw benchmark out put is stored.
Steve
Steven Pratt wrote:
> Nick Piggin wrote:
>
>> Steven Pratt wrote:
>>
>>> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
>>> significant degrade in random read for block devices using
>>> O_DIRECT. The drop occurs for all block sizes and ranges from
>>> 30%-40. CPU usage is also lower although it may already be so low
>>> as to be irrelavent.
>>
>>
>> Hi Steven, this is quite likely to be an io scheduler problem.
>> Is your test program rawread v2.1.5?
>
>
> This test was actually using 2.1.4, but the only difference in the
> 2.1.5 version is a fix for the test label array for the aio versions
> of the test. No functional change, just fixed the outputed test
> description.
>
>> What is the command line you are using to invoke the program?
>
>
> rawread -t6 -p8 -m1 -d2 -s4096 -n65536 -l1 -z -x
>
> Which you can find if you follow either results link and look in the
> benchmark directory where all raw benchmark out put is stored.
>
OK thanks, I can now reproduce this! I'll work on it.
Nick Piggin wrote:
> Steven Pratt wrote:
>
>> Nick Piggin wrote:
>>
>>> Steven Pratt wrote:
>>>
>>>> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
>>>> significant degrade in random read for block devices using
>>>> O_DIRECT. The drop occurs for all block sizes and ranges from
>>>> 30%-40. CPU usage is also lower although it may already be so low
>>>> as to be irrelavent.
>>>
>>> Hi Steven, this is quite likely to be an io scheduler problem.
>>> Is your test program rawread v2.1.5?
>>
>> This test was actually using 2.1.4, but the only difference in the
>> 2.1.5 version is a fix for the test label array for the aio versions
>> of the test. No functional change, just fixed the outputed test
>> description.
>>
>>> What is the command line you are using to invoke the program?
>>
>> rawread -t6 -p8 -m1 -d2 -s4096 -n65536 -l1 -z -x
>>
>> Which you can find if you follow either results link and look in the
>> benchmark directory where all raw benchmark out put is stored.
>
> OK thanks, I can now reproduce this! I'll work on it.
Looks like Andrew beat you to it. Both 2.5.70-mm7 and mm8 are back up
to the previous performance levels for random reads.
Steve
Steven Pratt wrote:
> Nick Piggin wrote:
>
>> Steven Pratt wrote:
>>
>>> Nick Piggin wrote:
>>>
>>>> Steven Pratt wrote:
>>>>
>>>>> Starting in 2.5.70-mm2 and continuing in the mm tree, there is a
>>>>> significant degrade in random read for block devices using
>>>>> O_DIRECT. The drop occurs for all block sizes and ranges from
>>>>> 30%-40. CPU usage is also lower although it may already be so low
>>>>> as to be irrelavent.
>>>>
>>>>
>>>> Hi Steven, this is quite likely to be an io scheduler problem.
>>>> Is your test program rawread v2.1.5?
>>>
>>>
>>> This test was actually using 2.1.4, but the only difference in the
>>> 2.1.5 version is a fix for the test label array for the aio versions
>>> of the test. No functional change, just fixed the outputed test
>>> description.
>>>
>>>> What is the command line you are using to invoke the program?
>>>
>>>
>>> rawread -t6 -p8 -m1 -d2 -s4096 -n65536 -l1 -z -x
>>>
>>> Which you can find if you follow either results link and look in the
>>> benchmark directory where all raw benchmark out put is stored.
>>
>>
>> OK thanks, I can now reproduce this! I'll work on it.
>
>
> Looks like Andrew beat you to it. Both 2.5.70-mm7 and mm8 are back up
> to the previous performance levels for random reads.
>
No, that was me ;)
Odd, I was still seeing a regression with mm7, but thats
fixed in mm8. Thanks for testing.