Re: [dpdk-dev] [PATCH] test: rely on EAL detection for core list

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Oct 19, 2021 at 11:52:32AM +0200, David Marchand wrote:
> On Mon, Oct 18, 2021 at 7:53 PM Bruce Richardson
> <bruce.richardson@intel.com> wrote:
> >
> > On Mon, Oct 18, 2021 at 07:01:36PM +0200, David Marchand wrote:
> > > Cores count has a direct impact on the time needed to complete unit
> > > tests.
> > >
> > > Currently, the core list used for unit test is enforced to "all cores on
> > > the system" with no way for (CI) users to adapt it.
> > > On the other hand, EAL default behavior (when no -c/-l option gets passed)
> > > is to start threads on as many cores available in the process cpu
> > > affinity.
> > >
> > > Remove logic from meson: users can then select where to run the tests by
> > > either running meson with a custom cpu affinity (using taskset/cpuset
> > > depending on OS) or by passing a --test-args option to meson.
> > >
> > > Example:
> > > $ sudo meson test -C build --suite fast-tests -t 3 --test-args "-l 0-3"
> > >
> > > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > > ---
> > > I wanted to post this as a RFC, but now, I wonder if all CI test RFC
> > > patches, so sending as a normal patch.
> > >
> > > ---
> > I really like this idea! Patch looks good other than it needs some doc
> > changes.
> 
> Wdyt of:
> 
> diff --git a/doc/guides/prog_guide/meson_ut.rst
> b/doc/guides/prog_guide/meson_ut.rst
> index fff88655dd..d35e0577c8 100644
> --- a/doc/guides/prog_guide/meson_ut.rst
> +++ b/doc/guides/prog_guide/meson_ut.rst
> @@ -47,9 +47,15 @@ Arguments of ``test()`` that can be provided in
> meson.build are as below:
> 
>  * ``is_parallel`` is used to run test case either in parallel or
> non-parallel mode.
>  * ``timeout`` is used to specify the timeout of test case.
> -* ``args`` is used to specify test specific parameters.
> +* ``args`` is used to specify test specific parameters (see note below).
>  * ``env`` is used to specify test specific environment parameters.
> 
> +Note: the content of meson ``--test-args`` option and the content of ``args``
> +are appended when invoking the DPDK test binary.
> +Because of this, it is recommended not to set any default coremask or memory
> +configuration in per test ``args`` and rather let users select what best fits
> +their environment. If a test can't run, then it should be skipped, as described
> +below.
> 
>  Dealing with skipped test cases
>  -------------------------------

That text is good. However, I also think we need an example above of using
test-args to limit core masks. How about also adding something like:

diff --git a/doc/guides/prog_guide/meson_ut.rst b/doc/guides/prog_guide/meson_ut.rst
index fff88655dd..4924066556 100644
--- a/doc/guides/prog_guide/meson_ut.rst
+++ b/doc/guides/prog_guide/meson_ut.rst
@@ -37,6 +37,13 @@ command::

     $ meson test --suite fast-tests

+If desired, additional arguments can be passed to the test run via the meson ``--test-args`` option.
+For example, tests will by default run on as many available cores as is needed for the test,
+starting with the lowest number core - generally core 0.
+To run the fast-tests suite using only cores 8 through 16, one can use::
+
+   $ meson test --suite fast-tests --test-args="-l 8-16"
+
 The meson command to list all available tests::

     $ meson test --list