Re: [PATCH 1/2] tests/migration: Make precopy fast

[Daniel P . Berrangé]

On Tue, Apr 18, 2023 at 02:20:27PM +0200, Juan Quintela wrote:
> Daniel P. Berrangé <berrange@redhat.com> wrote:
> > On Wed, Apr 12, 2023 at 04:20:00PM +0200, Juan Quintela wrote:
> >> Otherwise we do the 1st migration iteration at a too slow speed.
> >> 
> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> >> ---
> >>  tests/qtest/migration-test.c | 3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >> 
> >> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> >> index 3b615b0da9..7b05b0b7dd 100644
> >> --- a/tests/qtest/migration-test.c
> >> +++ b/tests/qtest/migration-test.c
> >> @@ -1348,6 +1348,7 @@ static void test_precopy_common(MigrateCommon *args)
> >>          migrate_qmp(from, args->connect_uri, "{}");
> >>      }
> >>  
> >> +    migrate_ensure_converge(from);
> >
> > This isn't right - it defeats the point of having the call to
> > migrate_ensure_non_converge() a few lines earlier.
> 
> Depends on what is the definiton or "right" O:-)
> 
> >>      if (args->result != MIG_TEST_SUCCEED) {
> >>          bool allow_active = args->result == MIG_TEST_FAIL;
> >> @@ -1365,8 +1366,6 @@ static void test_precopy_common(MigrateCommon *args)
> >>              wait_for_migration_pass(from);
> >>          }
> >>  
> >> -        migrate_ensure_converge(from);
> >> -
> >
> > The reason why we had it here was to ensure that we test more than
> > 1 iteration of migration. With this change, migrate will succeed
> > on the first pass IIUC, and so we won't be exercising the more
> > complex code path of repeated iterations.
> 
> Aha.
> 
> If that is the definition of "right", then I agree that my changes are
> wrong.
> 
> But then I think we should change how we do the test.  We should split
> this function (then same for postcopy, multifd, etc) to have to
> versions, one that want to have multiple rounds, and another that can
> finish as fast as possible.
> 
> This way we need to setup the 3MB/s only for the tests that we want to
> loop, and for the others put something faster.
> 
> 
> >
> > I do agree with the overall idea though. We have many many migration
> > test scenarios and we don't need all of them to be testing multiple
> > iterations - a couple would be sufficient.
> >
> > In fact we don't even need to be testing live migration for most
> > of the cases. All the TLS test cases could be run with guest CPUs
> > paused entirely removing any dirtying, since they're only interested
> > in the initial network handshake/setup process testnig.
> >
> > I had some patches I was finishing off just before I went on vacation
> > a few weeks ago which do this kind of optimization, which I can send
> > out shortly.
> 
> I will wait for your patches before I sent anything different.
> 
> I have local patches for doing something different, changing
> 
>       "-serial file:%s/src_serial "
> 
> and other friends to:
> 
>       "-serial file:%s/src_serial%pid "
> 
> So we are sure that two tests never "reuse" the socket, as it can create
> problems for example when doing the cancel and relaunching the
> destination.
> 
> But as said, will wait until you send your series to send anything.

I've just sent a new series which has some more differences and
improvements

https://lists.gnu.org/archive/html/qemu-devel/2023-04/msg03688.html


With regards,
Daniel
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