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

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On Intel, the firmware usually overrides the kernel power management
decision by auto-promoting the idle states.

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 ?

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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>>


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