Re: [PATCH] perf python: Set up callchain parameters for sessions

[sashiko-bot@kernel.org]

> perf.session never calls callchain_param_setup(), so callchains are
> resolved with callchain_param.record_mode left as CALLCHAIN_NONE rather
> than set from the sample type as in perf script and perf report.
> 
> On arm64 this loses frames: when a sample hits a function before it has
> pushed its frame record, its caller is only in the link register, and
> recovering it needs record_mode CALLCHAIN_FP. Comparing the callchain of
> every sample with perf script, on a frame pointer recording of a
> two-thread workload on arm64, 4 of 4494 samples miss a frame, e.g.:
> 
>   perf script: clock_gettime@plt <- now <- spin <- other_path
>   perf.session: clock_gettime@plt <- spin <- other_path
> 
> Call callchain_param_setup() once the session is created and, as perf
> script does, again as attrs are processed, for pipe mode. With that,
> all callchains match perf script on arm64, for frame pointer and DWARF
> recordings, from a file or a pipe. On x86 they matched before and still
> do.
> 
> Assisted-by: LLM
> Signed-off-by: Lalit Maganti <lalitmaganti@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261018081452.1014460-1-lalitmaganti@gmail.com?part=1