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

[Daniel Lezcano]

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 ?


> 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
> 


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