perf bench sched pipe: Add -G/--cgroups option

The -G/--cgroups option is to put sender and receiver in different
cgroups in order to measure cgroup context switch overheads.

Users need to make sure the cgroups exist and accessible.  The following
example should the effect of this change.  Please don't forget taskset
before the perf bench to measure cgroup switches properly.  Otherwise
each task would run on a different CPU and generate cgroup switches
regardless of this change.

  # perf stat -e context-switches,cgroup-switches \
  > taskset -c 0 perf bench sched pipe -l 10000 > /dev/null

   Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000':

              20,001      context-switches
                   2      cgroup-switches

         0.053449651 seconds time elapsed

         0.011286000 seconds user
         0.041869000 seconds sys

  # perf stat -e context-switches,cgroup-switches \
  > taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB > /dev/null

   Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB':

              20,001      context-switches
              20,001      cgroup-switches

         0.052768627 seconds time elapsed

         0.006284000 seconds user
         0.046266000 seconds sys

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20231017202342.1353124-1-namhyung@kernel.org

1 files changed, 19 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documentation/perf-bench.txt
index ca5789625cd2..8331bd28b10e 100644
--- a/tools/perf/Documentation/perf-bench.txt
+++ b/tools/perf/Documentation/perf-bench.txt
@@ -124,6 +124,14 @@ Options of *pipe*
 --loop=::
 Specify number of loops.
 
+-G::
+--cgroups=::
+Names of cgroups for sender and receiver, separated by a comma.
+This is useful to check cgroup context switching overhead.
+Note that perf doesn't create nor delete the cgroups, so users should
+make sure that the cgroups exist and are accessible before use.
+
+
 Example of *pipe*
 ^^^^^^^^^^^^^^^^^
 
@@ -141,6 +149,17 @@ Example of *pipe*
         Total time:0.016 sec
                 16.948000 usecs/op
                 59004 ops/sec
+
+% perf bench sched pipe -G AAA,BBB
+(executing 1000000 pipe operations between cgroups)
+# Running 'sched/pipe' benchmark:
+# Executed 1000000 pipe operations between two processes
+
+     Total time: 6.886 [sec]
+
+       6.886208 usecs/op
+         145217 ops/sec
+
 ---------------------
 
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