perf record: Extend --threads command line option

Extend --threads option in perf record command line interface.
The option can have a value in the form of masks that specify
CPUs to be monitored with data streaming threads and its layout
in system topology. The masks can be filtered using CPU mask
provided via -C option.

The specification value can be user defined list of masks. Masks
separated by colon define CPUs to be monitored by one thread and
affinity mask of that thread is separated by slash. For example:
<cpus mask 1>/<affinity mask 1>:<cpu mask 2>/<affinity mask 2>
specifies parallel threads layout that consists of two threads
with corresponding assigned CPUs to be monitored.

The specification value can be a string e.g. "cpu", "core" or
"package" meaning creation of data streaming thread for every
CPU or core or package to monitor distinct CPUs or CPUs grouped
by core or package.

The option provided with no or empty value defaults to per-cpu
parallel threads layout creating data streaming thread for every
CPU being monitored.

Document --threads option syntax and parallel data streaming modes
in Documentation/perf-record.txt.

Suggested-by: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Riccardo Mancini <rickyman7@gmail.com>
Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Riccardo Mancini <rickyman7@gmail.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Antonov <alexander.antonov@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/079e2619be70c465317cf7c9fdaf5fa069728c32.1642440724.git.alexey.v.bayduraev@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 32 insertions, 2 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index b9c6b112bf46..465be4e62a17 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -713,9 +713,39 @@ measurements:
  wait -n ${perf_pid}
  exit $?
 
---threads::
+--threads=<spec>::
 Write collected trace data into several data files using parallel threads.
-The option creates a data streaming thread for each CPU in the system.
+<spec> value can be user defined list of masks. Masks separated by colon
+define CPUs to be monitored by a thread and affinity mask of that thread
+is separated by slash:
+
+    <cpus mask 1>/<affinity mask 1>:<cpus mask 2>/<affinity mask 2>:...
+
+CPUs or affinity masks must not overlap with other corresponding masks.
+Invalid CPUs are ignored, but masks containing only invalid CPUs are not
+allowed.
+
+For example user specification like the following:
+
+    0,2-4/2-4:1,5-7/5-7
+
+specifies parallel threads layout that consists of two threads,
+the first thread monitors CPUs 0 and 2-4 with the affinity mask 2-4,
+the second monitors CPUs 1 and 5-7 with the affinity mask 5-7.
+
+<spec> value can also be a string meaning predefined parallel threads
+layout:
+
+    cpu    - create new data streaming thread for every monitored cpu
+    core   - create new thread to monitor CPUs grouped by a core
+    package - create new thread to monitor CPUs grouped by a package
+    numa   - create new threed to monitor CPUs grouped by a NUMA domain
+
+Predefined layouts can be used on systems with large number of CPUs in
+order not to spawn multiple per-cpu streaming threads but still avoid LOST
+events in data directory files. Option specified with no or empty value
+defaults to CPU layout. Masks defined or provided by the option value are
+filtered through the mask provided by -C option.
 
 include::intel-hybrid.txt[]