Re: [PATCH v2 0/4] Fix perf bench numa, futex and epoll to work with machines having #CPUs > 1K

Athira Rajeev
2022-04-07T04:31:47Z

> On 07-Apr-2022, at 6:05 AM, Ian Rogers <irogers@google.com> wrote:
>
> On Wed, Apr 6, 2022 at 10:51 AM Athira Rajeev
> <atrajeev@linux.vnet.ibm.com> wrote:
>>
>> The perf benchmark for collections: numa, futex and epoll
>> hits failure in system configuration with CPU's more than 1024.
>> These benchmarks uses "sched_getaffinity" and "sched_setaffinity"
>> in the code to work with affinity.
>>
>> Example snippet from numa benchmark:
>> <<>>
>> perf: bench/numa.c:302: bind_to_node: Assertion `!(ret)' failed.
>> Aborted (core dumped)
>> <<>>
>>
>> bind_to_node function uses "sched_getaffinity" to save the cpumask.
>> This fails with EINVAL because the default mask size in glibc is 1024.
>>
>> Similarly in futex and epoll benchmark, uses sched_setaffinity during
>> pthread_create with affinity. And since it returns EINVAL in such system
>> configuration, benchmark doesn't run.
>>
>> To overcome this 1024 CPUs mask size limitation of cpu_set_t,
>> change the mask size using the CPU_*_S macros ie, use CPU_ALLOC to
>> allocate cpumask, CPU_ALLOC_SIZE for size, CPU_SET_S to set mask bit.
>>
>> Fix all the relevant places in the code to use mask size which is large
>> enough to represent number of possible CPU's in the system.
>>
>> Fix parse_setup_cpu_list function in numa bench to check if input CPU
>> is online before binding task to that CPU. This is to fix failures where,
>> though CPU number is within max CPU, it could happen that CPU is offline.
>> Here, sched_setaffinity will result in failure when using cpumask having
>> that cpu bit set in the mask.
>>
>> Patch 1 and Patch 2 address fix for perf bench futex and perf bench
>> epoll benchmark. Patch 3 and Patch 4 address fix in perf bench numa
>> benchmark
>>
>> Athira Rajeev (4):
>> tools/perf: Fix perf bench futex to correct usage of affinity for
>> machines with #CPUs > 1K
>> tools/perf: Fix perf bench epoll to correct usage of affinity for
>> machines with #CPUs > 1K
>> tools/perf: Fix perf numa bench to fix usage of affinity for machines
>> with #CPUs > 1K
>> tools/perf: Fix perf bench numa testcase to check if CPU used to bind
>> task is online
>>
>> Changelog:
>> From v1 -> v2:
>> Addressed review comment from Ian Rogers to do
>> CPU_FREE in a cleaner way.
>> Added Tested-by from Disha Goel
>
>
> The whole set:
> Acked-by: Ian Rogers <irogers@google.com>

Thanks for checking Ian.

Athira.
>
> Thanks,
> Ian
>
>> tools/perf/bench/epoll-ctl.c | 25 ++++--
>> tools/perf/bench/epoll-wait.c | 25 ++++--
>> tools/perf/bench/futex-hash.c | 26 ++++--
>> tools/perf/bench/futex-lock-pi.c | 21 +++--
>> tools/perf/bench/futex-requeue.c | 21 +++--
>> tools/perf/bench/futex-wake-parallel.c | 21 +++--
>> tools/perf/bench/futex-wake.c | 22 ++++--
>> tools/perf/bench/numa.c | 105 ++++++++++++++++++-------
>> tools/perf/util/header.c | 43 ++++++++++
>> tools/perf/util/header.h | 1 +
>> 10 files changed, 242 insertions(+), 68 deletions(-)
>>
>> --
>> 2.35.1