From: Tommi Rantala tommi.t.rantala@nokia.com
commit f649bd9dd5d5004543bbc3c50b829577b49f5d75 upstream.
Since commit 3b2323c2c1c4 ("perf bench futex: Use cpumaps") the default number of threads the benchmark uses got changed from number of online CPUs to zero:
$ perf bench futex wake # Running 'futex/wake' benchmark: Run summary [PID 15930]: blocking on 0 threads (at [private] futex 0x558b8ee4bfac), waking up 1 at a time. [Run 1]: Wokeup 0 of 0 threads in 0.0000 ms [...] [Run 10]: Wokeup 0 of 0 threads in 0.0000 ms Wokeup 0 of 0 threads in 0.0004 ms (+-40.82%)
Restore the old behavior by grabbing the number of online CPUs via cpu->nr:
$ perf bench futex wake # Running 'futex/wake' benchmark: Run summary [PID 18356]: blocking on 8 threads (at [private] futex 0xb3e62c), waking up 1 at a time. [Run 1]: Wokeup 8 of 8 threads in 0.0260 ms [...] [Run 10]: Wokeup 8 of 8 threads in 0.0270 ms Wokeup 8 of 8 threads in 0.0419 ms (+-24.35%)
Fixes: 3b2323c2c1c4 ("perf bench futex: Use cpumaps") Signed-off-by: Tommi Rantala tommi.t.rantala@nokia.com Tested-by: Arnaldo Carvalho de Melo acme@redhat.com Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Darren Hart dvhart@infradead.org Cc: Davidlohr Bueso dave@stgolabs.net Cc: Jiri Olsa jolsa@redhat.com Cc: Mark Rutland mark.rutland@arm.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lore.kernel.org/lkml/20200305083714.9381-3-tommi.t.rantala@nokia.com Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/perf/bench/futex-wake.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/tools/perf/bench/futex-wake.c +++ b/tools/perf/bench/futex-wake.c @@ -43,7 +43,7 @@ static bool done = false, silent = false static pthread_mutex_t thread_lock; static pthread_cond_t thread_parent, thread_worker; static struct stats waketime_stats, wakeup_stats; -static unsigned int ncpus, threads_starting, nthreads = 0; +static unsigned int threads_starting, nthreads = 0; static int futex_flag = 0;
static const struct option options[] = { @@ -141,7 +141,7 @@ int bench_futex_wake(int argc, const cha sigaction(SIGINT, &act, NULL);
if (!nthreads) - nthreads = ncpus; + nthreads = cpu->nr;
worker = calloc(nthreads, sizeof(*worker)); if (!worker)