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6828d6929b
Tool events unnecessarily open a dummy perf event which is useless even with `perf record` which will still open a dummy event. Change the behavior of tool events so: - duration_time - call `rdclock` on open and then report the count as a delta since the start in evsel__read_counter. This moves code out of builtin-stat making it more general purpose. - user_time/system_time - open the fd as either `/proc/pid/stat` or `/proc/stat` for cases like system wide. evsel__read_counter will read the appropriate field out of the procfs file. These values were previously supplied by wait4, if the procfs read fails then the wait4 values are used, assuming the process/thread terminated. By reading user_time and system_time this way, interval mode, per PID and per CPU can be supported although there are restrictions given what the files provide (e.g. per PID can't be combined with per CPU). Opening any of the tool events for `perf record` is changed to return invalid. Signed-off-by: Ian Rogers <irogers@google.com> Tested-by: Weilin Wang <weilin.wang@intel.com> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: James Clark <james.clark@arm.com> Cc: Dmitrii Dolgov <9erthalion6@gmail.com> Cc: Ze Gao <zegao2021@gmail.com> Cc: Song Liu <song@kernel.org> Cc: Leo Yan <leo.yan@linux.dev> Signed-off-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20240503232849.17752-1-irogers@google.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.