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: Sat, 8 Jun 2024 12:36:04 +0530
From: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Namhyung Kim <namhyung@...nel.org>,
        LKML <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 7 Jun 2024, at 10:53 PM, Ian Rogers <irogers@...gle.com> wrote:
> 
> On Thu, Jun 6, 2024 at 9:44 PM Athira Rajeev
> <atrajeev@...ux.vnet.ibm.com> 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>
> 
> For the series:
> Reviewed-by: Ian Rogers <irogers@...gle.com>

Hi Ian

Thanks for the review 

Athira
> 
> Thanks,
> Ian
> 
>> ---
>> 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);
>> --
>> 2.43.0