6fe61cb4ae
Rename 'Switches' to 'Count' and document metrics shown for perf
sched latency output. Also add options possible with perf sched
latency.
Initially, after seeing the output of 'perf sched latency', the term
'Switches' seemed like it's the number of context switches-in for a
particular task, but upon going through the code, it was observed that
it's actually keeping track of number of times a delay was calculated so
that it is used in calculation of the average delay.
Actually, the switches here is a subset of number of context switches-in
because there are some cases where the count is not incremented in
switch-in handler 'add_sched_in_event'. For example when a task is
switched-in while it's state is not ready to run(!= THREAD_WAIT_CPU).
commit d9340c1db3f52460 ("perf sched: Display time in milliseconds,
reorganize output") changed it from the original count to switches.
So, renamed switches to count to make things a bit more clearer and
added the metrics description of latency in the document.
Reviewed-by: Aditya Gupta <adityag@linux.ibm.com>
Signed-off-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240328090005.8321-1-vineethr@linux.ibm.com
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.