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

[Thomas Huth <thuth@redhat.com>]

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