Messages in this thread | | | Date | Mon, 30 Apr 2012 22:11:45 -0700 | Subject | Re: High CPU usage of scheduler? | From | Dave Johansen <> |
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On Fri, Apr 27, 2012 at 8:23 AM, Dave Johansen <davejohansen@gmail.com> wrote: > On Thu, Apr 26, 2012 at 8:10 PM, Yong Zhang <yong.zhang0@gmail.com> 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 -- 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/
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