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From: Dirk Gouders <dirk@gouders.net>
To: Namhyung Kim <namhyung@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>
Cc: Dirk Gouders <dirk@gouders.net>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
LKML <linux-kernel@vger.kernel.org>, linux-perf-users@vger.kernel.org
Subject: [PATCH v2 2/3] perf bench sched pipe: add complete graph simulation
Date: Sat, 5 Apr 2025 14:00:07 +0200
Message-ID: <20250405120039.15953-3-dirk@gouders.net>
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Currently, we have only one worker function: the simulation of a ring
for token traversal.
Add another worker to simulate a complete graph (Kn) for token
traversal. A new option -K/--Kn can be used to use the new worker.
Those different workers could be interesting, because they produce
workload varieties noticeable by perf-report(1), for example:
(booted with mitigations=3Doff, 6 processes)
Ring simulation:
Samples: 92K of event 'cycles:P', Event count (approx.): 18690208287
Overhead Command Shared Object Symbol
13.16% sched-pipe [kernel.kallsyms] [k] timerqueue_add
7.10% sched-pipe [kernel.kallsyms] [k] read_hpet
3.36% sched-pipe [kernel.kallsyms] [k] _copy_from_iter
3.23% sched-pipe [kernel.kallsyms] [k] _copy_to_iter
2.64% sched-pipe [kernel.kallsyms] [k] vfs_write
2.55% sched-pipe [kernel.kallsyms] [k] vfs_read
Kn simulation:
Samples: 163K of event 'cycles:P', Event count (approx.): 100366721164
Overhead Command Shared Object Symbol
5.11% sched-pipe [kernel.kallsyms] [k] _copy_from_iter
4.90% sched-pipe [kernel.kallsyms] [k] queued_spin_lock_slowpath
3.99% sched-pipe [kernel.kallsyms] [k] _copy_to_iter
3.35% sched-pipe [kernel.kallsyms] [k] timerqueue_add
2.80% sched-pipe [kernel.kallsyms] [k] check_preemption_disabled
2.56% sched-pipe [kernel.kallsyms] [k] vfs_write
2.40% sched-pipe [kernel.kallsyms] [k] vfs_read
Signed-off-by: Dirk Gouders <dirk@gouders.net>
---
tools/perf/Documentation/perf-bench.txt | 5 +++
tools/perf/bench/sched-pipe.c | 60 +++++++++++++++++++++++--
2 files changed, 62 insertions(+), 3 deletions(-)
diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documenta=
tion/perf-bench.txt
index 8a651f2fe3aa..6f7df3d47821 100644
--- a/tools/perf/Documentation/perf-bench.txt
+++ b/tools/perf/Documentation/perf-bench.txt
@@ -130,6 +130,11 @@ process).
=20
Options of *pipe*
^^^^^^^^^^^^^^^^^
+-K::
+--Kn::
+Simulate a complete graph instead of a ring for sending tokens.
+Each process sends and receives tokens to/from every other process.
+
-l::
--loop=3D::
Specify number of loops.
diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c
index 28dd7f3a11b2..3c76e8249a9b 100644
--- a/tools/perf/bench/sched-pipe.c
+++ b/tools/perf/bench/sched-pipe.c
@@ -50,6 +50,8 @@ static bool threaded;
static unsigned int nr_threads =3D 2;
=20
static bool nonblocking;
+static bool Kn_mode; /* Toggle for ring mode -> complete graph mode */
+
static char *cgrp_names[2];
static struct cgroup *cgrps[2];
=20
@@ -90,6 +92,7 @@ static const struct option options[] =3D {
OPT_BOOLEAN('n', "nonblocking", &nonblocking, "Use non-blocking operation=
s"),
OPT_UINTEGER('p', "nprocs", &nr_threads, "Number of processes"),
OPT_UINTEGER('l', "loop", &loops, "Specify number of loops"),
+ OPT_BOOLEAN('K', "Kn", &Kn_mode, "Send tokens in a complete graph instea=
d of a ring."),
OPT_BOOLEAN('T', "threaded", &threaded, "Specify threads/process based ta=
sk setup"),
OPT_CALLBACK('G', "cgroups", NULL, "SEND,RECV",
"Put sender and receivers in given cgroups",
@@ -188,11 +191,55 @@ static inline int read_pipe(struct thread_data *td)
return ret;
}
=20
+/*
+ * Worker thread for processes forming a complete graph,
+ * sending tokens one to each other.
+ */
+static void *worker_thread_kn(void *__tdata)
+{
+ struct thread_data *this_thread =3D __tdata;
+ struct thread_data *all_threads =3D this_thread - this_thread->nr;
+
+ int ret, m =3D 0;
+ unsigned int i;
+ unsigned int t;
+
+ ret =3D enter_cgroup(this_thread->nr);
+ if (ret < 0) {
+ this_thread->cgroup_failed =3D true;
+ return NULL;
+ }
+
+ if (nonblocking) {
+ this_thread->epoll_ev.events =3D EPOLLIN;
+ this_thread->epoll_fd =3D epoll_create(1);
+ BUG_ON(this_thread->epoll_fd < 0);
+ BUG_ON(epoll_ctl(this_thread->epoll_fd, EPOLL_CTL_ADD, this_thread->pipe=
_read, &this_thread->epoll_ev) < 0);
+ }
+
+ for (i =3D 0; i < loops; i++) {
+ /* First: feed all other workers. */
+ for (t =3D 0; t < nr_threads; t++)
+ if (t !=3D this_thread->nr) {
+ ret =3D write(all_threads[t].pipe_write, &m, sizeof(int));
+ BUG_ON(ret !=3D sizeof(int));
+ }
+
+ /* Read a token from all other workers. */
+ for (t =3D 1; t < nr_threads; t++) {
+ ret =3D read_pipe(this_thread);
+ BUG_ON(ret !=3D sizeof(int));
+ }
+ }
+
+ return NULL;
+}
+
/*
* Worker thread for nodes forming a ring, receiving tokens from the left
* neighbor and sending them to the right one.
*/
-static void *worker_thread(void *__tdata)
+static void *worker_thread_ring(void *__tdata)
{
struct thread_data *this_thread =3D __tdata;
struct thread_data *first_thread =3D this_thread - this_thread->nr;
@@ -231,6 +278,9 @@ static void *worker_thread(void *__tdata)
return NULL;
}
=20
+/* Ring mode is the default. */
+void * (*worker_thread)(void *) =3D worker_thread_ring;
+
static struct thread_data *create_thread_data(void)
{
struct thread_data *threads;
@@ -279,6 +329,9 @@ int bench_sched_pipe(int argc, const char **argv)
=20
argc =3D parse_options(argc, argv, options, bench_sched_pipe_usage, 0);
=20
+ if (Kn_mode)
+ worker_thread =3D worker_thread_kn;
+
threads =3D create_thread_data();
=20
gettimeofday(&start, NULL);
@@ -331,8 +384,9 @@ int bench_sched_pipe(int argc, const char **argv)
=20
switch (bench_format) {
case BENCH_FORMAT_DEFAULT:
- printf("# Executed %d pipe operations between %u %s\n\n", loops,
- nr_threads, threaded ? "threads" : "processes");
+ printf("# Executed %d pipe operations (%s) between %u %s\n\n", loops,
+ Kn_mode ? "Kn" : "ring", nr_threads,
+ threaded ? "threads" : "processes");
=20
result_usec =3D diff.tv_sec * USEC_PER_SEC;
result_usec +=3D diff.tv_usec;
--=20
2.45.3