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Subject[PATCH 5.5 139/151] perf bench futex-wake: Restore thread count default to online CPU count
Date
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)

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