[PATCH] gcc parallel make check

[Jakub Jelinek]

On Thu, Sep 11, 2014 at 09:51:23AM +0200, Jakub Jelinek wrote:
> I can't find how to query the -jN value passed to make check by the user
> though, both $(MFLAGS) and $(MAKEFLAGS) only contain something like
> --jobserver-fds=3,5 -j from which it is not possible to find out how many
> goals would be the upper reasonable limit.  Running too many goals would
> waste time (once scheduled, the goal would only wildcard all the test, and
> for all of them find in the *-parallel directory the test has been run
> already), running too few could prevent good parallelization.

After a little googling, it seems there is no way to do that :(, unless
one e.g. attempts to find the command line of the topmost parent make
and scan it through ps or something.

There is an option to touch say *-parallel/finished file once any of the
check-parallel-gcc-{1,2,...} goals is done (because when it finishes, it
means all the tests for the particular check-$lang that are parallelizable
have either finished, or at least touched their file) and not start runtest
at all if finished already exists, but guess it would be still undesirable to have
tens of thousands of goals by default, so perhaps we could go with say
128 subgoals by default and have some env var to override it, so on the
really highly parallel boxes you'd specify
make -j512 -k check GCC_TEST_PARALLEL_SLOTS=512
or similar.

	Jakub