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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
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.