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

[Daniel P . Berrangé]

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.

>      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.


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.

>          /* We do this first, as it has a timeout to stop us
>           * hanging forever if migration didn't converge */
>          wait_for_migration_complete(from);


With regards,
Daniel
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