Re: [PATCH v4 00/10] tests/qtest: make migration-test massively faster

[Thomas Huth <thuth@redhat.com>]

On 01/06/2023 18.13, Daniel P. Berrangé wrote:
> This makes migration-test faster by observing that most of the pre-copy
> tests don't need to be doing a live migration. They get sufficient code
> coverage with the guest CPUs paused.
> 
> On my machine this cuts the overall execution time of migration-test
> from 13 minutes, down to 8 minutes, without sacrificing any noticeable
> code coverage.
> 
> Of the tests which do still run in live mode, some need to guarantee
> a certain number of iterions. This is achieved by running the 1
> iteration with an incredibly small bandwidth and max downtime to
> prevent convergance, and watching query-migrate for the reported
> iteration to increment. This guarantees that all the tests take at
> least 30 seconds to run per iteration required.
> 
> Watching for the iteration counter to flip is inefficient and not
> actually needed, except on the final iteration before starting
> convergance. On this final iteration we merely need to prove that
> some amount of already transferred data has been made dirty again.
> This in turn will guarantee that a further iteration is required
> beyond the current one. This proof is easy to achieve by monitoring
> the values at two distinct addresses in guest RAM, and can cut the
> 30 second duration down to 1 second for one of the iterations.
> 
> After this this second optimization the runtime is reduced from
> 8 minutes, down to 1 minute 40 seconds, which is pretty decent given
> the amount of coverage we're getting.

It's now ~1 week until the soft freeze, and the migration test still run for 
~8 minutes. This is still quite annoying. Could we please get one of the 
solutions merged before the soft freeze, either Daniel's or Peter's ?

  Thanks,
   Thomas