Re: High CPU usage of scheduler?

[Dave Johansen]

On Mon, Apr 30, 2012 at 10:11 PM, Dave Johansen <davejohansen@xxxxxxxxx> wrote:
> On Fri, Apr 27, 2012 at 8:23 AM, Dave Johansen <davejohansen@xxxxxxxxx> wrote:
>> On Thu, Apr 26, 2012 at 8:10 PM, Yong Zhang <yong.zhang0@xxxxxxxxx> wrote:
>>>
>>> On Thu, Apr 26, 2012 at 03:08:51PM -0700, Dave Johansen wrote:
>>> > I am looking into moving an application from RHEL 5 to RHEL 6 and I
>>> > noticed an unexpected increase in CPU usage. A little digging has led
>>> > me to believe that the scheduler may be the culprit.
>>> >
>>> > I created the attached test_select_work.c file to test this out. I
>>> > compiled it with the following command on RHEL 5:
>>> >
>>> > cc test_select_work.c -O2 -DSLEEP_TYPE=0 -Wall -Wextra -lm -lpthread
>>> > -o test_select_work
>>>
>>> Hmm...Do both RHEL 5 and RHEL 6 have high resolution timer enabled?
>>>
>>> If not, could you please try to boot the one which enable high resolution
>>> timer with 'highres=off' to see if things change?
>>
>> Yes, RHEL 6 has CONFIG_HIGH_RES_TIMERS=y. I rebooted and used the
>> 'highres=off' in grub and got the following results:
>>
>>   ./test_select_work 1000 10000 300 4
>>   time_per_iteration: min: 3130.1 us avg: 3152.2 us max: 3162.2 us
>> stddev: 15.0 us
>>   ./test_select_work 1000 10000 300 8
>>   time_per_iteration: min: 4314.6 us avg: 4407.9 us max: 4496.3 us
>> stddev: 60.6 us
>>   ./test_select_work 1000 10000 300 40
>>   time_per_iteration: min: 8901.7 us avg: 9056.5 us max: 9121.3 us
>> stddev: 57.5 us
>>
>> Any other info that might be helpful?
>>
>> Thanks,
>> Dave
>
> I made some improvements to the program to make comparisons a bit
> easier and the standard deviation a bit more meaningful. It is
> available in a git repo at git://github.com/daveisfera/test_sleep.git
>
> I tried sending results from running this updated program on several
> OS versions, but it must have been rejected by the filters. The info
> can be found in the bugzilla:
> https://bugzilla.redhat.com/show_bug.cgi?id=812148
>
> Is there any more data I can gather or tests that I can run that can
> help diagnose this problem?
>
> Thanks in advance for any help,
> Dave

I also added the images and descriptions to the stackexchange
question, so they can be more easily viewed there:
http://unix.stackexchange.com/questions/37391/high-cpu-usage-with-cfs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/