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perf bench futex-wake: Restore thread count default to online CPU count 

ANBZ: #1893

commit f649bd9dd5 upstream.

Since commit 3b2323c2c1 ("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: 3b2323c2c1 ("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: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Yihao Wu <wuyihao@linux.alibaba.com>
Link: https://gitee.com/anolis/cloud-kernel/pulls/630
This commit is contained in:
Tommi Rantala 2020-03-05 10:37:13 +02:00 committed by Joseph Qi
parent ba6a15068d
commit f7a1d692be
1 changed files with 2 additions and 2 deletions
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4
tools/perf/bench/futex-wake.c
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@ -42,7 +42,7 @@ static bool done = false, silent = false, fshared = 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[] = {
@ -140,7 +140,7 @@ int bench_futex_wake(int argc, const char **argv)
sigaction(SIGINT, &act, NULL);
if (!nthreads)
nthreads = ncpus;
nthreads = cpu->nr;
worker = calloc(nthreads, sizeof(*worker));
if (!worker)