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Message-ID: <20250731132615.938435-6-yuzhuo@google.com>
Date: Thu, 31 Jul 2025 06:26:15 -0700
From: Yuzhuo Jing <yuzhuo@...gle.com>
To: Davidlohr Bueso <dave@...olabs.net>, "Paul E . McKenney" <paulmck@...nel.org>,
Josh Triplett <josh@...htriplett.org>, Frederic Weisbecker <frederic@...nel.org>,
Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, Joel Fernandes <joelagnelf@...dia.com>,
Boqun Feng <boqun.feng@...il.com>, Uladzislau Rezki <urezki@...il.com>,
Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>, Zqiang <qiang.zhang@...ux.dev>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
Liang Kan <kan.liang@...ux.intel.com>, Yuzhuo Jing <yzj@...ch.edu>,
Yuzhuo Jing <yuzhuo@...gle.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-kernel@...r.kernel.org,
rcu@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [PATCH v1 5/5] perf bench: Add documentation for 'sync rcu' suite
Add documentation for 'perf bench sync rcu'. This benchmark has three
modes or subcommands that takes positional arguments. In addition,
*kernel* module parameters are directly specified in the form of
"name=value", without "--name". Multiple subsections are thus added to
the 'sync' section for illustration.
Signed-off-by: Yuzhuo Jing <yuzhuo@...gle.com>
---
tools/perf/Documentation/perf-bench.txt | 131 ++++++++++++++++++++++++
1 file changed, 131 insertions(+)
diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documentation/perf-bench.txt
index 8331bd28b10e..786c6e6880f5 100644
--- a/tools/perf/Documentation/perf-bench.txt
+++ b/tools/perf/Documentation/perf-bench.txt
@@ -49,6 +49,9 @@ SUBSYSTEM
'sched'::
Scheduler and IPC mechanisms.
+'sync'::
+ Synchronization primitives.
+
'syscall'::
System call performance (throughput).
@@ -162,6 +165,134 @@ Example of *pipe*
---------------------
+SUITES FOR 'sync'
+~~~~~~~~~~~~~~~~~
+*rcu*::
+Suite for RCU performance. Depends on rcuscale kernel module.
+This benchmark has three modes: once, range, ratio. Usage is defined as below.
+
+'perf bench sync rcu' [options..] [-- <command>..]
+'perf bench sync rcu' [options..] once <gp_type> [<param=value>..] [-- <command>..]
+'perf bench sync rcu' [options..] range <gp_type> [<param=range>..] [-- <command>..]
+'perf bench sync rcu' [options..] ratio <gp_type> <total> <param1_range> <param1_name> <param2_name> [<param=value>..] [-- <command>..]
+
+Modes for *rcu*
+^^^^^^^^^^^^^^^
+
+default::
+Run 'once sync'.",
+
+once::
+Run benchmark once, with all parameters passed through to the kernel rcuscale
+module.
+
+range::
+Run benchmark multiple times, with parameters as ranges. Range format is
+defined as start[:end[:step]], inclusive, non-negative. The benchmark
+instantiates all combinations of all ranges.
+
+ratio::
+Run benchmark that changes the ratio between two parameters. 'total' specifies
+the sum of 'param1' and 'param2', and 'param1_range' is the range of 'param1'
+values. 'param2' is calculated by 'total-param1'. Additional non-range
+parameters may also be specified.
+
+Positional arguments for *rcu*
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+gp_type::
+The type of grace period to use: sync, async, exp (expedited)
+
+param::
+Any parameter of the rcuscale kernel module, except for "gp_exp",
+"gp_async" and "block_start" that are managed by this benchmark.
+Valid options can be found from "modinfo rcuscale".
+
+command::
+A child command to run during the experiment. If the command line
+string contains {READER,WRITER,KFREE}_TASKS placeholders, they will be
+substituted with the tasks PIDs, separated by comma.
+
+Options for *rcu*
+^^^^^^^^^^^^^^^^^
+-c::
+--cooldown::
+Sleep time between each experiment (default: 3 seconds).
+
+-n::
+--dryrun::
+Dry run mode. Do not run experiments, but instead print what parameter
+combination will run.
+
+--child-delay=::
+Wait for child startup before starting experiment (default: 1 second).
+
+--debugfs=::
+Debugfs mount point used to interact with the rcuscale kernel module. (default:
+/sys/kernel/debug).
+
+--hist::
+Show the histogram of writer durations.
+
+Example of *rcu*
+^^^^^^^^^^^^^^^^
+
+---------------------
+% perf bench sync rcu once exp nreaders=1 nwriters=1
+# Running 'sync/rcu' benchmark:
+Running experiment with options: gp_exp=1 nreaders=1 nwriters=1
+Experiment finished.
+Average grace-period duration: 124.236 microseconds
+Minimum grace-period duration: 8.783
+50th percentile grace-period duration: 9.033
+90th percentile grace-period duration: 9.665
+99th percentile grace-period duration: 20.911
+Maximum grace-period duration: 6025.167
+
+% perf bench sync rcu range exp nreaders=1 nwriters=1 writer_cpu_offset=0:1 -- \
+ perf stat -e ipi:ipi_send_cpu,rcu:rcu_grace_period \
+ -t READER_TASKS,WRITER_TASKS
+# Running 'sync/rcu' benchmark:
+Running experiment with options: gp_exp=1 nreaders=1 nwriters=1 writer_cpu_offset=0
+Running child command: perf stat -e ipi:ipi_send_cpu,rcu:rcu_grace_period -t 2061441,2061442
+
+ Performance counter stats for thread id '2061441,2061442':
+
+ 2400 ipi:ipi_send_cpu
+ 100 rcu:rcu_grace_period
+
+ 6.006040148 seconds time elapsed
+
+Experiment finished.
+Waiting for child process to exit.
+Average grace-period duration: 301.177 microseconds
+Minimum grace-period duration: 9.064
+50th percentile grace-period duration: 9.394
+90th percentile grace-period duration: 10.977
+99th percentile grace-period duration: 5926.781
+Maximum grace-period duration: 6011.067
+Cooling down (3s)..
+
+Running experiment with options: gp_exp=1 nreaders=1 nwriters=1 writer_cpu_offset=1
+Running child command: perf stat -e ipi:ipi_send_cpu,rcu:rcu_grace_period -t 2061461,2061462
+
+ Performance counter stats for thread id '2061461,2061462':
+
+ 2144 ipi:ipi_send_cpu
+ 201 rcu:rcu_grace_period
+
+ 6.006110747 seconds time elapsed
+
+Experiment finished.
+Waiting for child process to exit.
+Average grace-period duration: 12.23 microseconds
+Minimum grace-period duration: 9.134
+50th percentile grace-period duration: 9.475
+90th percentile grace-period duration: 11.897
+99th percentile grace-period duration: 38.057
+Maximum grace-period duration: 67.19
+---------------------
+
SUITES FOR 'syscall'
~~~~~~~~~~~~~~~~~~
*basic*::
--
2.50.1.565.gc32cd1483b-goog
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