Re: grep-3.7.98-c9ac on Linux/s390x

[Jim Meyering]

On Sun, Jul 3, 2022 at 5:50 AM Bruno Haible <bruno@clisp.org> wrote:
>
> On Linux/s390x (emulated with qemu-system-s390x) all tests pass, except one:
>
>
> FAIL: long-pattern-perf
> =======================
>
> ...
> + base_ms=1250
> ++ user_time_ 1 grep -f re-10x in
> ...
> + b10x_ms=81800
> + returns_ 1 expr 1250 '<' 81800 / 20
> 1
> + fail=1
> + Exit 1
> + set +e
> + exit 1
> + exit 1
> + remove_tmp_
> + __st=1
> + cleanup_
> + :
> + test '' = yes
> + cd /home/bruno/grep-3.7.98-c9ac/build-64/tests
> + chmod -R u+rwx 
> /home/bruno/grep-3.7.98-c9ac/build-64/tests/gt-long-pattern-perf.PZ1I
> + rm -rf /home/bruno/grep-3.7.98-c9ac/build-64/tests/gt-long-pattern-perf.PZ1I
> + exit 1
> FAIL long-pattern-perf (exit status: 1)
>
>
> Apparently the timings are not so reliable in a qemu emulated system.

Thanks for reporting that.
Is that reproducible?
That test allows some leeway, letting a 10x increase in regex size
evoke a 20x runtime increase.
Accommodating this fringe environment (at least with that one sample
timing) would require raising that well past 60x, which would get too
close to the old 100x perf hit that's supposed to be avoided, now.