[LTP] [PATCH v2] copy_file_range03: comparing timestamp in tst_timespec_diff

[Li Wang]

On Mon, Sep 6, 2021 at 4:59 PM Cyril Hrubis <chrubis@suse.cz> wrote:

> Hi!
> > -     updated_timestamp = get_timestamp(fd_dest);
> > +     timestamp2 = get_timestamp(fd_dest);
> >
> > -     if (timestamp == updated_timestamp)
> > +     diff = tst_timespec_diff(timestamp1, timestamp2);
> > +
> > +     if (!diff.tv_sec && !diff.tv_nsec)
> >               tst_brk(TFAIL, "copy_file_range did not update
> timestamp.");
>
> So as we changed the code to sleep for 1.5 sec I guess that we can
> expect the difference to be at least 1 second because:
>
> - the minimal granularity is 1s in which case we will get exactly 1s in
>   the diff
>
> - if the granularity is greater, we will get a bit more than 1s
>
> So I would go for something as:
>
>         long long diff_us = tst_timespec_diff_us(timestamp2, timestamp1);
>
>         if (diff_us >= 1000000 && diff_us <= 2000000)
>                 tst_res(TPASS, "...");
>
> Which expects that the difference between timestamps is in a sane range
> not that it just have been changed.
>

Theoretically, this is correct, but I'm fearing that the process might
cost more time on performing with different system loads.

This means 'diff_us <= 2000000' is an unreliable condition to
many virtual machines. That largely depends on the system
scheduler at that moment as well.



>
> >       tst_res(TPASS, "copy_file_range sucessfully updated the
> timestamp");
> > --
> > 2.31.1
> >
> >
> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp
>
> --
> Cyril Hrubis
> chrubis@suse.cz
>
>

-- 
Regards,
Li Wang
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