schbench: scale down worker threads to num_cpus by default

The default number of worker threads is just num_cpus, but the workers
are per message thread.  So if you pass -m 2, you'll end up with 2x the
number of workers, which is a surprise.

This commit changes the default to scale down the workers when -m is
increased.  You can still use -t to manually set the worker count.

Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/schbench.c b/schbench.c
index 76cecc3..937f1f2 100644
--- a/schbench.c
+++ b/schbench.c
@@ -1350,7 +1350,10 @@ int main(int ac, char **av)
 	parse_options(ac, av);
 
 	if (worker_threads == 0) {
-		worker_threads = get_nprocs();
+		unsigned long num_cpus = get_nprocs();
+
+		worker_threads = (num_cpus + message_threads - 1) / message_threads;
+
 		fprintf(stderr, "setting worker threads to %d\n", worker_threads);
 	}