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

[Jan Stancek]

----- 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
> > 
> 
> 
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