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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
From: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
In-Reply-To: <92752ed4-0091-4a98-8af7-dd58bc5432bc@linux.ibm.com>
Date: Wed, 12 Jun 2024 17:41:22 +0530
Cc: Jiri Olsa <jolsa@kernel.org>, Adrian Hunter <adrian.hunter@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users <linux-perf-users@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, akanksha@linux.ibm.com,
        Madhavan Srinivasan <maddy@linux.ibm.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Disha Goel <disgoel@linux.vnet.ibm.com>
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Message-Id: <8AA105EF-A7DD-4890-9878-46E473743EAE@linux.vnet.ibm.com>
References: <20240607044354.82225-1-atrajeev@linux.vnet.ibm.com>
 <92752ed4-0091-4a98-8af7-dd58bc5432bc@linux.ibm.com>
To: Disha Goel <disgoel@linux.ibm.com>, Namhyung Kim <namhyung@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ian Rogers <irogers@google.com>


> On 10 Jun 2024, at 7:52=E2=80=AFPM, Disha Goel <disgoel@linux.ibm.com> =
wrote:
>=20
> On 07/06/24 10:13 am, Athira Rajeev wrote:
>=20
>> Perf bench futex fails as below when attempted to run on
>> on a powerpc system:
>>=20
>>  ./perf bench futex all
>>  Running futex/hash benchmark...
>> Run summary [PID 626307]: 80 threads, each operating on 1024 =
[private] futexes for 10 secs.
>>=20
>> perf: pthread_create: No such file or directory
>>=20
>> 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 =3D 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.
>>=20
>> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
>=20
> 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.
>=20
> For the series:
> Tested-by: Disha Goel <disgoel@linux.ibm.com>

Thanks Disha for testing the patchset.=20

Athira
>=20
>> ---
>>  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(-)
>>=20
>> 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 =3D perf_cpu_map__nr(cpu);
>> + nrcpus =3D cpu__max_cpu().cpu;
>>   cpuset =3D CPU_ALLOC(nrcpus);
>>   BUG_ON(!cpuset);
>>   size =3D 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 =3D  perf_cpu_map__nr(cpu);
>> + int nrcpus =3D  cpu__max_cpu().cpu;
>>   size_t size;
>>     threads_starting =3D 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 =3D perf_cpu_map__nr(cpu);
>> + int nrcpus =3D cpu__max_cpu().cpu;
>>   size_t size;
>>     threads_starting =3D 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 =3D perf_cpu_map__nr(cpu);
>> + int nrcpus =3D cpu__max_cpu().cpu;
>>   size_t size;
>>     threads_starting =3D 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 =3D perf_cpu_map__nr(cpu);
>> + int nrcpus =3D cpu__max_cpu().cpu;
>>   threads_starting =3D params.nthreads;
>>     cpuset =3D CPU_ALLOC(nrcpus);