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When retire_latency value is used in a metric formula, evsel would fork a 'perf record' process with "-e" and "-W" options. 'perf record' will collect required retire_latency values in parallel while 'perf stat' is collecting counting values. At the point of time that 'perf stat' stops counting, evsel would stop 'perf record' by sending sigterm signal to 'perf record' process. Sampled data will be processed to get retire latency value. Another thread is required to synchronize between 'perf stat' and 'perf record' when we pass data through pipe. Retire_latency evsel is not opened for 'perf stat' so that there is no counter wasted on it. This commit includes code suggested by Namhyung to adjust reading size for groups that include retire_latency evsels. In current :R parsing implementation, the parser would recognize events with retire_latency modifier and insert them into the evlist like a normal event. Ideally, we need to avoid counting these events. In this commit, at the time when a retire_latency evsel is read, set the retire latency value processed from the sampled data to count value. This sampled retire latency value will be used for metric calculation and final event count print out. No special metric calculation and event print out code required for retire_latency events. Reviewed-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Weilin Wang <weilin.wang@intel.com> Acked-by: Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Caleb Biggers <caleb.biggers@intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Perry Taylor <perry.taylor@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Samantha Alt <samantha.alt@intel.com> Link: https://lore.kernel.org/r/20240720062102.444578-4-weilin.wang@intel.com [ Squashed the 3rd and 4th commit in the series to keep it building patch by patch ] [ Constified the 'struct perf_tool' pointer in process_sample_event() ] [ Use perf_tool__init(&tool, false) to address a segfault I reported and Ian/Weilin diagnosed ] Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.