[LTP] [PATCH] dio: reduce the number of cycles

Cyril Hrubis chrubis@suse.cz
Thu Jun 15 15:17:52 CEST 2017

> >> > What's the reliability after the patch btw? What is the actual
> >> > percentage of undetected failures for at least 10 runs of the test?
> >>
> >> I ran diotest30 10 times with "-i 100" and 8 of them failed. IIRC, it
> >> was not 100% reproduced either when I first saw the test failure in
> >> 4.10-rc kernel testing. So I think ~80% probability to reproduce is
> >> fine.
> >
> > Fair enough I've added this paragraph to the commit message and pushed,
> > thanks.
> Hmm, it does not takes about 100 minutes, without this change, it
> takes almost 9mins. After applying, only 50secs.
> That's probably my description misleading you, sorry about that. Since
> you have already submitted this patch, so, let it go.

Strange, it does take about ~10 minutes after the patch is applied for
me and about ~100 before at least for diotest6, diotest3 is a bit faster
with ~20 minutes before and ~4 minutes after. That is on NUMA machine
with 24 CPUs and 16GB RAM and /tmp on Btrfs.

The diotest6 appears to be taking about ~45 minutes in our automated
framework before this patch and diotest3 takes about 3 minutes.

On my workstation the diotest3 takes ~5 minutes after the patch and
diotest06 takes ~45 minutes. That is much more modest machine with just
4GB RAM and 4 CPUs.

So I would say that the resulting time depends on many factors, most
notably the underlying I/O device, fileystem, number of CPUs and RAM.

Cyril Hrubis

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