Re: [PATCH 0/2] tests/migration: Fix migration-test slowdown

[Thomas Huth]

On 18/04/2023 15.19, Juan Quintela wrote:
> Thomas Huth <thuth@redhat.com> wrote:
> > On 18/04/2023 13.42, Juan Quintela wrote:
> > > Thomas Huth <thuth@redhat.com> wrote:
> > > > On 12/04/2023 16.19, Juan Quintela wrote:
> > > > > Since commit:
> > > > > commit 1bfc8dde505f1e6a92697c52aa9b09e81b54c78f
> > > > > Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > > > > Date:   Mon Mar 6 15:26:12 2023 +0000
> > > > >        tests/migration: Tweek auto converge limits check
> > > > >        Thomas found an autoconverge test failure where the
> > > > >        migration completed before the autoconverge had kicked in.
> > > > >        [...]
> > > > > migration-test has become very slow.
> > > > > On my laptop, before that commit migration-test takes 2min10seconds
> > > > > After that commit, it takes around 11minutes
> > > > > We can't revert it because it fixes a real problem when the host
> > > > > machine is overloaded.  See the comment on test_migrate_auto_converge().
> > > >
> > > > Thanks, your patches decrease the time to run the migration-test from
> > > > 16 minutes down to 5 minutes on my system, that's a great improvement,
> > > > indeed!
> > > >
> > > > Tested-by: Thomas Huth <thuth@redhat.com>
> > > Thanks
> > >
> > > > (though 5 minutes are still quite a lot for qtests ... maybe some
> > > > other parts could be moved to only run with g_test_slow() ?)
> > > Hi
> > > Could you gime the output of:
> > > time for i in $(./tests/qtest/migration-test -l | grep "^/"); do
> > > echo $i; time ./tests/qtest/migration-test -p $i; done
> > > To see what tests are taking so long on your system?
> > > On my system (i9900K processor, i.e. not the latest) and
> > > auto_converge
> > > moved to slow the total of the tests take a bit more than 1 minute.
> >
> > This is with both of your patches applied:
...
> > real    5m32,733s
> > user    7m24,380s
> > sys     1m50,801s
>
> Ouch.
>
> Can I ask:
> - what is your machine?  It is specially slow?

It's a 4 year old T480s ThinkPad laptop.

>    Otherwise I want to know why it is happening.
>
> - as what is going slow to you is postcopy, can you told me what is this
>    setting?
>
> # we want postcopy to work for normal users
> vm.unprivileged_userfaultfd = 1

$ sysctl vm.unprivileged_userfaultfd
sysctl: cannot stat /proc/sys/vm/unprivileged_userfaultfd: No such file or 
directory

> And if it is not set, just change it and retest.

Seems like it is not available on RHEL 8 yet :-(

Shall we maybe disable the postcopy tests if unprivileged_userfaultfd is not 
available?

 Thomas