Re: [PATCH 11/12] perf mem record: Request PERF_SAMPLE_CPU by default

[sashiko-bot@kernel.org]

> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> The data-type profiling per-sample stream keys cross-CPU contention on
> sample->cpu: without PERF_SAMPLE_CPU the cpu field is the (u32)-1 "no
> CPU info" sentinel, documented as such in perf_session__deliver_event(),
> and same-instance reads and writes from different cores are
> indistinguishable from same-CPU traffic, so pahole's false-sharing
> detector cannot tell them apart.
> 
> builtin-record.c already defines --sample-cpu and 'perf mem record'
> forwards unknown options to the record parser, so passing it explicitly
> works today; make it the default, next to the -d (addr) and -W (weight)
> the command already requests, documenting it in perf-mem(1).
> 
> The rec_argv array is sized as nine arguments per memory PMU plus the
> user arguments, not counting the arguments __cmd_record() adds itself,
> up to eight with all the optional flags.  On PMUs with separate load and
> store events the four event arguments plus the fixed ones already filled
> the array to its last slot, so this new argument would write past it;
> reserve space for the fixed arguments explicitly.
> 
> Assisted-by: LLM
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260916183215.54305-1-acme@kernel.org?part=11