From 60035a3981a7f9d965df81a48a07b94e52ccd54f Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 16 Apr 2025 18:29:19 +0200 Subject: tools/perf: Allow to select the number of hash buckets Add the -b/ --buckets argument to specify the number of hash buckets for the private futex hash. This is directly passed to prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, buckets, immutable) and must return without an error if specified. The `immutable' is 0 by default and can be set to 1 via the -I/ --immutable argument. The size of the private hash is verified with PR_FUTEX_HASH_GET_SLOTS. If PR_FUTEX_HASH_GET_SLOTS failed then it is assumed that an older kernel was used without the support and that the global hash is used. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250416162921.513656-20-bigeasy@linutronix.de --- tools/perf/bench/futex-wake.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'tools/perf/bench/futex-wake.c') diff --git a/tools/perf/bench/futex-wake.c b/tools/perf/bench/futex-wake.c index 49b3c89b0b35..8d6107f7cd94 100644 --- a/tools/perf/bench/futex-wake.c +++ b/tools/perf/bench/futex-wake.c @@ -42,6 +42,7 @@ static unsigned int threads_starting; static int futex_flag = 0; static struct bench_futex_parameters params = { + .nbuckets = -1, /* * How many wakeups to do at a time. * Default to 1 in order to make the kernel work more. @@ -50,6 +51,8 @@ static struct bench_futex_parameters params = { }; static const struct option options[] = { + OPT_INTEGER( 'b', "buckets", ¶ms.nbuckets, "Specify amount of hash buckets"), + OPT_BOOLEAN( 'I', "immutable", ¶ms.buckets_immutable, "Make the hash buckets immutable"), OPT_UINTEGER('t', "threads", ¶ms.nthreads, "Specify amount of threads"), OPT_UINTEGER('w', "nwakes", ¶ms.nwakes, "Specify amount of threads to wake at once"), OPT_BOOLEAN( 's', "silent", ¶ms.silent, "Silent mode: do not display data/details"), @@ -93,6 +96,7 @@ static void print_summary(void) params.nthreads, waketime_avg / USEC_PER_MSEC, rel_stddev_stats(waketime_stddev, waketime_avg)); + futex_print_nbuckets(¶ms); } static void block_threads(pthread_t *w, struct perf_cpu_map *cpu) -- cgit v1.2.3