linux-kernel - Re: [PATCH 1/3] tools/perf: Fix the nrcpus in perf bench futex to enable the run when all CPU's are not online

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Date: Mon, 10 Jun 2024 19:52:35 +0530
From: Disha Goel <disgoel@...ux.ibm.com>
To: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, acme@...nel.org,
        jolsa@...nel.org, adrian.hunter@...el.com, irogers@...gle.com,
        namhyung@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, akanksha@...ux.ibm.com,
        maddy@...ux.ibm.com, kjain@...ux.ibm.com, disgoel@...ux.vnet.ibm.com
Subject: Re: [PATCH 1/3] tools/perf: Fix the nrcpus in perf bench futex to
 enable the run when all CPU's are not online

On 07/06/24 10:13 am, Athira Rajeev wrote:

> Perf bench futex fails as below when attempted to run on
> on a powerpc system:
>
>   ./perf bench futex all
>   Running futex/hash benchmark...
> Run summary [PID 626307]: 80 threads, each operating on 1024 [private] futexes for 10 secs.
>
> perf: pthread_create: No such file or directory
>
> In the setup where this perf bench was ran, difference was that
> partition had 640 CPU's, but not all CPUs were online. 80 CPUs
> were online. While blocking the threads with futex_wait, code
> sets the affinity using cpumask. The cpumask size used is 80
> which is picked from "nrcpus = perf_cpu_map__nr(cpu)". Here the
> benchmark reports fail while setting affinity for cpu number which
> is greater than 80 or higher, because it attempts to set a bit
> position which is not allocated on the cpumask. Fix this by changing
> the size of cpumask to number of possible cpus and not the number
> of online cpus.
>
> Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>

Thanks for the fix patches, Athira.
I have tested all three patches on a power machine (both small and max config),
and the perf bench futex and epoll tests run fine.

For the series:
Tested-by: Disha Goel <disgoel@...ux.ibm.com>

> ---
>   tools/perf/bench/futex-hash.c          | 2 +-
>   tools/perf/bench/futex-lock-pi.c       | 2 +-
>   tools/perf/bench/futex-requeue.c       | 2 +-
>   tools/perf/bench/futex-wake-parallel.c | 2 +-
>   tools/perf/bench/futex-wake.c          | 2 +-
>   5 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/bench/futex-hash.c b/tools/perf/bench/futex-hash.c
> index 0c69d20efa32..b472eded521b 100644
> --- a/tools/perf/bench/futex-hash.c
> +++ b/tools/perf/bench/futex-hash.c
> @@ -174,7 +174,7 @@ int bench_futex_hash(int argc, const char **argv)
>   	pthread_attr_init(&thread_attr);
>   	gettimeofday(&bench__start, NULL);
>   
> -	nrcpus = perf_cpu_map__nr(cpu);
> +	nrcpus = cpu__max_cpu().cpu;
>   	cpuset = CPU_ALLOC(nrcpus);
>   	BUG_ON(!cpuset);
>   	size = CPU_ALLOC_SIZE(nrcpus);
> diff --git a/tools/perf/bench/futex-lock-pi.c b/tools/perf/bench/futex-lock-pi.c
> index 7a4973346180..0416120c091b 100644
> --- a/tools/perf/bench/futex-lock-pi.c
> +++ b/tools/perf/bench/futex-lock-pi.c
> @@ -122,7 +122,7 @@ static void create_threads(struct worker *w, struct perf_cpu_map *cpu)
>   {
>   	cpu_set_t *cpuset;
>   	unsigned int i;
> -	int nrcpus =  perf_cpu_map__nr(cpu);
> +	int nrcpus =  cpu__max_cpu().cpu;
>   	size_t size;
>   
>   	threads_starting = params.nthreads;
> diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c
> index d9ad736c1a3e..aad5bfc4fe18 100644
> --- a/tools/perf/bench/futex-requeue.c
> +++ b/tools/perf/bench/futex-requeue.c
> @@ -125,7 +125,7 @@ static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
>   {
>   	cpu_set_t *cpuset;
>   	unsigned int i;
> -	int nrcpus = perf_cpu_map__nr(cpu);
> +	int nrcpus = cpu__max_cpu().cpu;
>   	size_t size;
>   
>   	threads_starting = params.nthreads;
> diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c
> index b66df553e561..90a5b91bf139 100644
> --- a/tools/perf/bench/futex-wake-parallel.c
> +++ b/tools/perf/bench/futex-wake-parallel.c
> @@ -149,7 +149,7 @@ static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
>   {
>   	cpu_set_t *cpuset;
>   	unsigned int i;
> -	int nrcpus = perf_cpu_map__nr(cpu);
> +	int nrcpus = cpu__max_cpu().cpu;
>   	size_t size;
>   
>   	threads_starting = params.nthreads;
> diff --git a/tools/perf/bench/futex-wake.c b/tools/perf/bench/futex-wake.c
> index 690fd6d3da13..49b3c89b0b35 100644
> --- a/tools/perf/bench/futex-wake.c
> +++ b/tools/perf/bench/futex-wake.c
> @@ -100,7 +100,7 @@ static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
>   	cpu_set_t *cpuset;
>   	unsigned int i;
>   	size_t size;
> -	int nrcpus = perf_cpu_map__nr(cpu);
> +	int nrcpus = cpu__max_cpu().cpu;
>   	threads_starting = params.nthreads;
>   
>   	cpuset = CPU_ALLOC(nrcpus);