rcutorture: Enable concurrent rcutorture runs

The rcutorture tests run by default range from using one CPU to using
sixteen of them.  Therefore, rcutorture testing could be sped up
significantly simply by running the kernels in parallel.  Building
them in parallel is not all that helpful: "make -j" is usually a
better bet.  So this commit takes a new "--cpus" argument that
specifies how many CPUs rcutorture is permitted to use for its
parallel runs.  The default of zero does sequential runs as before.

The bin-packing is minimal, and will be grossly suboptimal for
some configurations.  However, powers of two work reasonably well.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh
index 587561d7c035..9b17e810ddc3 100644
--- a/tools/testing/selftests/rcutorture/bin/functions.sh
+++ b/tools/testing/selftests/rcutorture/bin/functions.sh
@@ -96,6 +96,7 @@ identify_qemu () {
 		echo qemu-system-ppc64
 	else
 		echo Cannot figure out what qemu command to use! 1>&2
+		echo file $1 output: $u
 		# Usually this will be one of /usr/bin/qemu-system-*
 		# Use RCU_QEMU_CMD environment variable or appropriate
 		# argument to top-level script.