[LTP] [PATCH 2/2] starvation: skip test on slow kernel

[Petr Vorel]

> Hi Li,

> > Systems with slow kernel configurations may not meet
> > the performance requirements necessary for the starvation
> > test to produce valid results.

> > Skipping the test ensures that it runs only on systems
> > where its results are meaningful.
> ...
> > +	if (tst_has_slow_kconfig())
> > +		tst_brk(TCONF, "Skip test due to slow kernel configuration");
> > +

> Reviewed-by: Petr Vorel <pvorel@suse.cz>

> I suppose you have strong reason for this (e.g. it's failing on some slow
> machine). I'm testing it on emulated riscv64 to see whether it's needed to be
> skipped. Because due CONFIG_LATENCYTOP it will always be skipped on Tumbleweed.

OK, I was able to reproduce TFAIL on emulated riscv64, which runs ~ 4m 30s, with
timeout increased to 0h 05m 46s:

tst_tmpdir.c:316: TINFO: Using /tmp/LTP_sta3UIB6E as tmpdir (tmpfs filesystem)
tst_test.c:1893: TINFO: LTP version: 20240930
tst_test.c:1897: TINFO: Tested kernel: 6.12.6-1-default #1 SMP PREEMPT_DYNAMIC Thu Dec 19 17:23:25 UTC 2024 (fb072de) riscv64
tst_kconfig.c:88: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:667: TINFO: CONFIG_LATENCYTOP kernel option detected which might slow the execution
tst_test.c:1728: TINFO: Timeout per run is 0h 02m 00s
starvation.c:98: TINFO: Setting affinity to CPU 0
starvation.c:52: TINFO: CPU did 120000000 loops in 226566us
tst_test.c:1736: TINFO: Updating max runtime to 0h 03m 46s
tst_kconfig.c:88: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:667: TINFO: CONFIG_LATENCYTOP kernel option detected which might slow the execution
tst_test.c:1728: TINFO: Timeout per run is 0h 05m 46s
starvation.c:148: TFAIL: Scheduller starvation reproduced.

But it works on emulated x86_64.

tst_tmpdir.c:316: TINFO: Using /tmp/LTP_staIt0g73 as tmpdir (tmpfs filesystem)
tst_test.c:1893: TINFO: LTP version: 20240930-148-g4539bfbc7
tst_test.c:1897: TINFO: Tested kernel: 6.13.0-rc4-1.g4a5c6a6-default #1 SMP PREEMPT_DYNAMIC Sun Dec 22 22:11:35 UTC 2024 (4a5c6a6) x86_64
tst_kconfig.c:88: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:667: TINFO: CONFIG_LATENCYTOP kernel option detected which might slow the execution
tst_test.c:1728: TINFO: Timeout per run is 0h 02m 00s
starvation.c:98: TINFO: Setting affinity to CPU 0
starvation.c:52: TINFO: CPU did 120000000 loops in 34189us
tst_test.c:1736: TINFO: Updating max runtime to 0h 00m 34s
tst_kconfig.c:88: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:667: TINFO: CONFIG_LATENCYTOP kernel option detected which might slow the execution
tst_test.c:1728: TINFO: Timeout per run is 0h 02m 34s
starvation.c:150: TPASS: Haven't reproduced scheduller starvation.

I wonder if we can quit with TCONF only on certain runtime increase. We would
also need to take -l (number of loops into an account).

Kind regards,
Petr

> Kind regards,
> Petr