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Namhyung Kim
30626e0844
To save memory usage, it needs to reduce the number of entries in the proc filesystem. It's using /proc/<PID>/task directory to traverse threads in the process and then kernel creates /proc/<PID>/task/<TID> entries. After that it checks the thread info using the /proc/<TID>/status file rather than /proc/<PID>/task/<TID>/status. As far as I can see, they are the same and contain all the info we need. Using the latter eliminates the unnecessary /proc/<TID> entry. This can be useful especially a large number of threads are used in the system. In my experiment around 1KB of memory on average was saved for each thread (which is not a thread group leader). To do this, pass both pid and tid to perf_event_prepare_comm() if it knows them. In case it doesn't know, passing 0 as pid will do the old way. Signed-off-by: Namhyung Kim <namhyung@kernel.org> Acked-by: Jiri Olsa <jolsa@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: https://lore.kernel.org/r/20210202090118.2008551-2-namhyung@kernel.org 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 Restructured Text 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.