Re: [PATCH v2] perf test record.sh: Raise limit of open file descriptors

[Michael Petlan <mpetlan@redhat.com>]

Hello Arnaldo,
what do you think about the v2?
Thanks.
Michael

On Thu, 30 Nov 2023, vmolnaro@redhat.com wrote:
> From: Veronika Molnarova <vmolnaro@redhat.com>
> 
> Subtest for system-wide record with '--threads=cpu' option fails due
> to a limit of open file descriptors on systems with 128 or more CPUs
> as the default limit is set to 1024.
> 
> The number of open file descriptors should be slightly above
> nmb_events*nmb_cpus + nmb_cpus(for perf.data.n) + 4*nmb_cpus(for pipes),
> which equals 8*nmb_cpus. Therefore, temporarily raise the limit to
> 16*nmb_cpus for the test.
> 
> Signed-off-by: Veronika Molnarova <vmolnaro@redhat.com>
> ---
>  tools/perf/tests/shell/record.sh | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index 4fbc74805d52..8acd55d09a1c 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -11,6 +11,14 @@ err=0
>  perfdata=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
>  testprog="perf test -w thloop"
>  testsym="test_loop"
> +default_fd_limit=$(ulimit -n)
> +# With option --threads=cpu the number of open file descriptors should be
> +# equal to sum of:    nmb_cpus * nmb_events (2+dummy),
> +#                     nmb_threads for perf.data.n (equal to nmb_cpus) and
> +#                     2*nmb_cpus of pipes = 4*nmb_cpus (each pipe has 2 ends)
> +# All together it needs 8*nmb_cpus file descriptors plus some are also used 
> +# outside of testing, thus raising the limit to 16*nmb_cpus
> +min_fd_limit=$(($(getconf _NPROCESSORS_ONLN) * 16))
>  
>  cleanup() {
>    rm -rf "${perfdata}"
> @@ -154,10 +162,18 @@ test_workload() {
>    echo "Basic target workload test [Success]"
>  }
>  
> +# raise the limit of file descriptors to minimum
> +if [[ $default_fd_limit -lt $min_fd_limit ]]; then
> +	ulimit -n $min_fd_limit
> +fi
> +
>  test_per_thread
>  test_register_capture
>  test_system_wide
>  test_workload
>  
> +# restore the default value
> +ulimit -n $default_fd_limit
> +
>  cleanup
>  exit $err
> -- 
> 2.41.0
> 
> 
>