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

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Message-Id: <CF7DB310-9E7C-4084-9A7C-317D4D4004EF@linux.vnet.ibm.com>
Date:   Thu, 7 Apr 2022 10:01:07 +0530
From:   Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     maddy@...ux.vnet.ibm.com,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Nageswara Sastry <rnsastry@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users@...r.kernel.org, jolsa@...nel.org,
        kjain@...ux.ibm.com, disgoel@...ux.vnet.ibm.com,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 0/4] Fix perf bench numa, futex and epoll to work with
 machines having #CPUs > 1K



> On 07-Apr-2022, at 6:05 AM, Ian Rogers <irogers@...gle.com> wrote:
> 
> On Wed, Apr 6, 2022 at 10:51 AM Athira Rajeev
> <atrajeev@...ux.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@...gle.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