Re: [PATCH] tests/qtest: optimize qtest_get_machines

[Markus Armbruster <armbru@redhat.com>]

Steve Sistare <steven.sistare@oracle.com> writes:

> qtest_get_machines returns the machines supported by the QEMU binary
> described by an environment variable and caches the result.  If the
> next call to qtest_get_machines passes the same variable name, the cached
> result is returned, but if the name changes, the caching is defeated.
> To make caching more effective, remember the path of the QEMU binary
> instead.  Different env vars, eg QTEST_QEMU_BINARY_SRC and
> QTEST_QEMU_BINARY_DST, usually resolve to the same path.
>
> Before the optimization, the test /x86_64/migration/precopy/unix/plain
> exec's QEMU and calls query-machines 3 times.  After optimization, that
> only happens once.  This does not significantly speed up the tests, but
> it reduces QTEST_LOG output, and launches fewer QEMU instances, making
> it easier to debug problems.
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

I guess this is a followup to an observation I made during review of my
[PATCH 1/5] qtest/qom-test: Plug memory leak with -p:

    Message-ID: <87h5ymdzrf.fsf@pond.sub.org>
    https://lore.kernel.org/qemu-devel/87h5ymdzrf.fsf@pond.sub.org/

Appreciated!