multifd/tcp/zlib intermittent abort (was: Re: [PULL 00/18] migration queue)

[Peter Maydell]

On Mon, 14 Mar 2022 at 19:44, Peter Maydell <peter.maydell@linaro.org> wrote:
> On Mon, 14 Mar 2022 at 18:58, Peter Maydell <peter.maydell@linaro.org> wrote:
> > I just hit the abort case, narrowing it down to the
> > /i386/migration/multifd/tcp/zlib case, which can hit this without
> > any other tests being run:
>
> > This test seems to fail fairly frequently. I'll try a bisect...
>
> On this s390 machine, this test has been intermittent since
> it was first added in commit 7ec2c2b3c1 ("multifd: Add zlib compression
> multifd support") in 2019.

I have tried (on current master) runs of various of the other
migration tests, and:
 * /i386/migration/multifd/tcp/zstd completed 1170 iterations without
   failing
 * /i386/migration/precopy/tcp completed 4669 iterations without
   failing
 * /i386/migration/multifd/tcp/zlib fails usually within the first
   10 iterations (the most I ever saw it manage was 32)

So whatever this is, it seems like it might be specific to the
zlib code somehow ?

thanks
-- PMM