[LTP] [PATCH V3] ltp: Add a zero latency constraint for the timer tests library

Jan Stancek jstancek@redhat.com
Wed Dec 13 21:42:13 CET 2017 


----- Original Message -----
> On 12/12/2017 16:21, Daniel Lezcano wrote:
> > 
> > On Intel, the firmware usually overrides the kernel power management
> > decision by auto-promoting the idle states.

Yeah, I was saving BIOS as last option.

> > 
> > So it is possible it is the case for you. With a process keeping the CPU
> > "busy" that prevents the firmware to go to a deepest idle state.
> > 
> > I see it is a Xeon platform. You can try by checking the
> > performance/power balance option in the BIOS. AFAIR, there is
> > performance aggressive, power aggressive, balanced-performance+ and
> > balanced-power+ and balanced.
> > 
> > Can you check this option ?
> 
> So ? any news from the front ?

Not yet, it's a remote system and I can't get into BIOS atm.

> 
> > On 12/12/2017 16:04, Jan Stancek wrote:
> >>
> >>
> >> ----- Original Message -----
> >>> On 12/12/2017 15:48, Jan Stancek wrote:
> >>>> Hi,
> >>>>
> >>>> I'm running into similar problem on "Dell Precision 5820 tower", with
> >>>> Intel(R) Xeon(R) W-2133 CPU @ 3.60GHz, but I can't find any /proc /sys
> >>>> knob that would help.
> >>>>
> >>>> # uname -r
> >>>> 4.14.5
> >>>>
> >>>> # cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>> performance
> >>>>
> >>>> Any timer related tests are reliably failing on longer timeouts:
> >>>> ---
> >>>> tst_test.c:934: INFO: Timeout per run is 0h 05m 00s
> >>>> tst_timer_test.c:356: INFO: CLOCK_MONOTONIC resolution 1ns
> >>>> tst_timer_test.c:368: INFO: prctl(PR_GET_TIMERSLACK) = 50us
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 1000us 500 iterations,
> >>>> threshold 450.01us
> >>>> tst_timer_test.c:318: INFO: min 1095us, max 1098us, median 1096us, trunc
> >>>> mean 1095.99us (discarded 25)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 2000us 500 iterations,
> >>>> threshold 450.01us
> >>>> tst_timer_test.c:318: INFO: min 2062us, max 2138us, median 2137us, trunc
> >>>> mean 2135.98us (discarded 25)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 5000us 300 iterations,
> >>>> threshold 450.04us
> >>>> tst_timer_test.c:318: INFO: min 5262us, max 5263us, median 5262us, trunc
> >>>> mean 5262.20us (discarded 15)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 10000us 100 iterations,
> >>>> threshold 450.33us
> >>>> tst_timer_test.c:318: INFO: min 10318us, max 10471us, median 10471us,
> >>>> trunc
> >>>> mean 10469.07us (discarded 5)
> >>>> tst_timer_test.c:321: FAIL: poll() slept for too long
> >>>
> >>> Are you running the tests with this zero latency patch included ?
> >>
> >> Yes, I'm running ltp release 20170929, which has your patch.
> >>
> >> ...
> >> [pid 18276] 09:59:21.379883 open("/dev/cpu_dma_latency", O_WRONLY) = 3
> >> [pid 18276] 09:59:21.379906 write(3, "\0\0\0\0", 4) = 4
> >> ...
> >>
> >> I tried it without that patch, and it started failing more with smaller
> >> timeouts.
> >>
> >> Regards,
> >> Jan
> >>
> >>>
> >>>
> >>>> SCHED_OTHER or SCHED_FIFO -> FAIL
> >>>> intel_idle.max_cstate=0 processor.max_cstate=1 -> FAIL
> >>>> echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo -> FAIL
> >>>> idle=halt -> FAIL
> >>>> idle=poll -> FAIL
> >>>>
> >>>> Only thing I found to help is to keep CPU slightly busy with
> >>>>   taskset -c 1 sh -c "while [ True ]; do usleep 100; done"
> >>>>
> >>>> After that it started to PASS:
> >>>>
> >>>> # taskset -c 1 ./poll02
> >>>> tst_test.c:934: INFO: Timeout per run is 0h 05m 00s
> >>>> tst_timer_test.c:356: INFO: CLOCK_MONOTONIC resolution 1ns
> >>>> tst_timer_test.c:368: INFO: prctl(PR_GET_TIMERSLACK) = 50us
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 1000us 500 iterations,
> >>>> threshold 450.01us
> >>>> tst_timer_test.c:318: INFO: min 1004us, max 1325us, median 1072us, trunc
> >>>> mean 1149.29us (discarded 25)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 2000us 500 iterations,
> >>>> threshold 450.01us
> >>>> tst_timer_test.c:318: INFO: min 2007us, max 2326us, median 2075us, trunc
> >>>> mean 2158.64us (discarded 25)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 5000us 300 iterations,
> >>>> threshold 450.04us
> >>>> tst_timer_test.c:318: INFO: min 5006us, max 5345us, median 5074us, trunc
> >>>> mean 5146.84us (discarded 15)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 10000us 100 iterations,
> >>>> threshold 450.33us
> >>>> tst_timer_test.c:318: INFO: min 10004us, max 10364us, median 10075us,
> >>>> trunc
> >>>> mean 10128.61us (discarded 5)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 25000us 50 iterations,
> >>>> threshold 451.29us
> >>>> tst_timer_test.c:318: INFO: min 25006us, max 25359us, median 25072us,
> >>>> trunc
> >>>> mean 25137.48us (discarded 2)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 100000us 10 iterations,
> >>>> threshold 537.00us
> >>>> tst_timer_test.c:318: INFO: min 100010us, max 100372us, median 100125us,
> >>>> trunc mean 100167.78us (discarded 1)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>> tst_timer_test.c:275: INFO: poll() sleeping for 1000000us 2 iterations,
> >>>> threshold 4400.00us
> >>>> tst_timer_test.c:318: INFO: min 1000843us, max 1000920us, median
> >>>> 1000843us,
> >>>> trunc mean 1000843.00us (discarded 1)
> >>>> tst_timer_test.c:333: PASS: Measured times are within thresholds
> >>>>
> >>>> Summary:
> >>>> passed   7
> >>>> failed   0
> >>>> skipped  0
> >>>> warnings 0
> >>>>
> >>>> Any ideas?
> >>>>
> >>>> Regards,
> >>>> Jan
> >>>>
> >>>
> >>>
> >>> --
> >>>  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
> >>>
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> >>>
> >>>
> >>> --
> >>> Mailing list info: https://lists.linux.it/listinfo/ltp
> >>>
> > 
> > 
> 
> 
> --
>  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
> 
> Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter |
> <http://www.linaro.org/linaro-blog/> Blog
> 
>

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