Re: [RFC PATCH 3/3] tests/qtest/migration-test: Enable test_ignore_shared

[Peter Xu <peterx@redhat.com>]

On Mon, May 27, 2024 at 12:11:45PM -0300, Fabiano Rosas wrote:
> Peter Xu <peterx@redhat.com> writes:
> 
> > On Mon, May 27, 2024 at 09:42:28AM -0300, Fabiano Rosas wrote:
> >> However, there is an issue here still on all archs - which might very
> >> well have been the original issue - which is the fact that the
> >> containers on the Gitlab CI have limits on shared memory usage.
> >> Unfortunately we cannot enable this test for the CI, so it needs a check
> >> on the GITLAB_CI environment variable.
> >
> > Another option is we teach migration-test to detect whether memory_size of
> > shmem is available, skip if not.  It can be a sequence of:
> >
> >   memfd_create()
> >   fallocate()
> >   ret = madvise(MADV_POPULATE_WRITE)
> >
> > To be run at the entry of migration-test, and skip all use_shmem=true tests
> > if ret != 0, or any step failed above.
> 
> There are actually two issues:
> 
> 1) Trying to run a test that needs more shmem than available in the
> container. This is covered well by your suggestion.
> 
> 2) Trying to use some shmem while another test has already consumed all
> shmem. I'm not sure if this can be done reliably as the tests run in
> parallel.

Maybe we can also make that check to be per-test, then when use_shmem=true
the test populates the shmem file before using, skip if population fails.
And if it succeeded, using that file in that test should be reliable.

-- 
Peter Xu