From: Gabriele Monaco <gmonaco@redhat.com>
To: linux-kernel@vger.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Shuah Khan <shuah@kernel.org>,
linux-kselftest@vger.kernel.org
Cc: Gabriele Monaco <gmonaco@redhat.com>, Ingo Molnar <mingo@kernel.org>
Subject: [PATCH v6 3/3] rseq/selftests: Add test for mm_cid compaction
Date: Mon, 10 Feb 2025 16:32:52 +0100 [thread overview]
Message-ID: <20250210153253.460471-4-gmonaco@redhat.com> (raw)
In-Reply-To: <20250210153253.460471-1-gmonaco@redhat.com>
A task in the kernel (task_mm_cid_work) runs somewhat periodically to
compact the mm_cid for each process. Add a test to validate that it runs
correctly and timely.
The test spawns 1 thread pinned to each CPU, then each thread, including
the main one, runs in short bursts for some time. During this period, the
mm_cids should be spanning all numbers between 0 and nproc.
At the end of this phase, a thread with high enough mm_cid (>= nproc/2)
is selected to be the new leader, all other threads terminate.
After some time, the only running thread should see 0 as mm_cid, if that
doesn't happen, the compaction mechanism didn't work and the test fails.
The test never fails if only 1 core is available, in which case, we
cannot test anything as the only available mm_cid is 0.
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
---
tools/testing/selftests/rseq/.gitignore | 1 +
tools/testing/selftests/rseq/Makefile | 2 +-
.../selftests/rseq/mm_cid_compaction_test.c | 200 ++++++++++++++++++
3 files changed, 202 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/rseq/mm_cid_compaction_test.c
diff --git a/tools/testing/selftests/rseq/.gitignore b/tools/testing/selftests/rseq/.gitignore
index 16496de5f6ce4..2c89f97e4f737 100644
--- a/tools/testing/selftests/rseq/.gitignore
+++ b/tools/testing/selftests/rseq/.gitignore
@@ -3,6 +3,7 @@ basic_percpu_ops_test
basic_percpu_ops_mm_cid_test
basic_test
basic_rseq_op_test
+mm_cid_compaction_test
param_test
param_test_benchmark
param_test_compare_twice
diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index 5a3432fceb586..ce1b38f46a355 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -16,7 +16,7 @@ OVERRIDE_TARGETS = 1
TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_test param_test \
param_test_benchmark param_test_compare_twice param_test_mm_cid \
- param_test_mm_cid_benchmark param_test_mm_cid_compare_twice
+ param_test_mm_cid_benchmark param_test_mm_cid_compare_twice mm_cid_compaction_test
TEST_GEN_PROGS_EXTENDED = librseq.so
diff --git a/tools/testing/selftests/rseq/mm_cid_compaction_test.c b/tools/testing/selftests/rseq/mm_cid_compaction_test.c
new file mode 100644
index 0000000000000..7ddde3b657dd6
--- /dev/null
+++ b/tools/testing/selftests/rseq/mm_cid_compaction_test.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: LGPL-2.1
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stddef.h>
+
+#include "../kselftest.h"
+#include "rseq.h"
+
+#define VERBOSE 0
+#define printf_verbose(fmt, ...) \
+ do { \
+ if (VERBOSE) \
+ printf(fmt, ##__VA_ARGS__); \
+ } while (0)
+
+/* 0.5 s */
+#define RUNNER_PERIOD 500000
+/* Number of runs before we terminate or get the token */
+#define THREAD_RUNS 5
+
+/*
+ * Number of times we check that the mm_cid were compacted.
+ * Checks are repeated every RUNNER_PERIOD.
+ */
+#define MM_CID_COMPACT_TIMEOUT 10
+
+struct thread_args {
+ int cpu;
+ int num_cpus;
+ pthread_mutex_t *token;
+ pthread_barrier_t *barrier;
+ pthread_t *tinfo;
+ struct thread_args *args_head;
+};
+
+static void __noreturn *thread_runner(void *arg)
+{
+ struct thread_args *args = arg;
+ int i, ret, curr_mm_cid;
+ cpu_set_t cpumask;
+
+ CPU_ZERO(&cpumask);
+ CPU_SET(args->cpu, &cpumask);
+ ret = pthread_setaffinity_np(pthread_self(), sizeof(cpumask), &cpumask);
+ if (ret) {
+ errno = ret;
+ perror("Error: failed to set affinity");
+ abort();
+ }
+ pthread_barrier_wait(args->barrier);
+
+ for (i = 0; i < THREAD_RUNS; i++)
+ usleep(RUNNER_PERIOD);
+ curr_mm_cid = rseq_current_mm_cid();
+ /*
+ * We select one thread with high enough mm_cid to be the new leader.
+ * All other threads (including the main thread) will terminate.
+ * After some time, the mm_cid of the only remaining thread should
+ * converge to 0, if not, the test fails.
+ */
+ if (curr_mm_cid >= args->num_cpus / 2 &&
+ !pthread_mutex_trylock(args->token)) {
+ printf_verbose(
+ "cpu%d has mm_cid=%d and will be the new leader.\n",
+ sched_getcpu(), curr_mm_cid);
+ for (i = 0; i < args->num_cpus; i++) {
+ if (args->tinfo[i] == pthread_self())
+ continue;
+ ret = pthread_join(args->tinfo[i], NULL);
+ if (ret) {
+ errno = ret;
+ perror("Error: failed to join thread");
+ abort();
+ }
+ }
+ pthread_barrier_destroy(args->barrier);
+ free(args->tinfo);
+ free(args->token);
+ free(args->barrier);
+ free(args->args_head);
+
+ for (i = 0; i < MM_CID_COMPACT_TIMEOUT; i++) {
+ curr_mm_cid = rseq_current_mm_cid();
+ printf_verbose("run %d: mm_cid=%d on cpu%d.\n", i,
+ curr_mm_cid, sched_getcpu());
+ if (curr_mm_cid == 0)
+ exit(EXIT_SUCCESS);
+ usleep(RUNNER_PERIOD);
+ }
+ exit(EXIT_FAILURE);
+ }
+ printf_verbose("cpu%d has mm_cid=%d and is going to terminate.\n",
+ sched_getcpu(), curr_mm_cid);
+ pthread_exit(NULL);
+}
+
+int test_mm_cid_compaction(void)
+{
+ cpu_set_t affinity;
+ int i, j, ret = 0, num_threads;
+ pthread_t *tinfo;
+ pthread_mutex_t *token;
+ pthread_barrier_t *barrier;
+ struct thread_args *args;
+
+ sched_getaffinity(0, sizeof(affinity), &affinity);
+ num_threads = CPU_COUNT(&affinity);
+ tinfo = calloc(num_threads, sizeof(*tinfo));
+ if (!tinfo) {
+ perror("Error: failed to allocate tinfo");
+ return -1;
+ }
+ args = calloc(num_threads, sizeof(*args));
+ if (!args) {
+ perror("Error: failed to allocate args");
+ ret = -1;
+ goto out_free_tinfo;
+ }
+ token = malloc(sizeof(*token));
+ if (!token) {
+ perror("Error: failed to allocate token");
+ ret = -1;
+ goto out_free_args;
+ }
+ barrier = malloc(sizeof(*barrier));
+ if (!barrier) {
+ perror("Error: failed to allocate barrier");
+ ret = -1;
+ goto out_free_token;
+ }
+ if (num_threads == 1) {
+ fprintf(stderr, "Cannot test on a single cpu. "
+ "Skipping mm_cid_compaction test.\n");
+ /* only skipping the test, this is not a failure */
+ goto out_free_barrier;
+ }
+ pthread_mutex_init(token, NULL);
+ ret = pthread_barrier_init(barrier, NULL, num_threads);
+ if (ret) {
+ errno = ret;
+ perror("Error: failed to initialise barrier");
+ goto out_free_barrier;
+ }
+ for (i = 0, j = 0; i < CPU_SETSIZE && j < num_threads; i++) {
+ if (!CPU_ISSET(i, &affinity))
+ continue;
+ args[j].num_cpus = num_threads;
+ args[j].tinfo = tinfo;
+ args[j].token = token;
+ args[j].barrier = barrier;
+ args[j].cpu = i;
+ args[j].args_head = args;
+ if (!j) {
+ /* The first thread is the main one */
+ tinfo[0] = pthread_self();
+ ++j;
+ continue;
+ }
+ ret = pthread_create(&tinfo[j], NULL, thread_runner, &args[j]);
+ if (ret) {
+ errno = ret;
+ perror("Error: failed to create thread");
+ abort();
+ }
+ ++j;
+ }
+ printf_verbose("Started %d threads.\n", num_threads);
+
+ /* Also main thread will terminate if it is not selected as leader */
+ thread_runner(&args[0]);
+
+ /* only reached in case of errors */
+out_free_barrier:
+ free(barrier);
+out_free_token:
+ free(token);
+out_free_args:
+ free(args);
+out_free_tinfo:
+ free(tinfo);
+
+ return ret;
+}
+
+int main(int argc, char **argv)
+{
+ if (!rseq_mm_cid_available()) {
+ fprintf(stderr, "Error: rseq_mm_cid unavailable\n");
+ return -1;
+ }
+ if (test_mm_cid_compaction())
+ return -1;
+ return 0;
+}
--
2.48.1
next prev parent reply other threads:[~2025-02-10 15:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-10 15:32 [PATCH v6 0/3] sched: Restructure task_mm_cid_work for predictability Gabriele Monaco
2025-02-10 15:32 ` [PATCH v6 1/3] sched: Compact RSEQ concurrency IDs with reduced threads and affinity Gabriele Monaco
2025-02-13 14:56 ` Mathieu Desnoyers
2025-02-18 7:53 ` Peter Zijlstra
2025-02-20 15:08 ` [tip: sched/urgent] " tip-bot2 for Mathieu Desnoyers
2025-02-10 15:32 ` [PATCH v6 2/3] sched: Move task_mm_cid_work to mm delayed work Gabriele Monaco
2025-02-13 6:52 ` kernel test robot
2025-02-13 13:25 ` Gabriele Monaco
2025-02-13 13:55 ` Mathieu Desnoyers
2025-02-13 14:37 ` Gabriele Monaco
2025-02-13 14:52 ` Mathieu Desnoyers
2025-02-13 14:54 ` Gabriele Monaco
2025-02-13 17:31 ` Mathieu Desnoyers
2025-02-14 6:44 ` Gabriele Monaco
2025-02-10 15:32 ` Gabriele Monaco [this message]
2025-02-10 16:09 ` [PATCH v6 0/3] sched: Restructure task_mm_cid_work for predictability Mathieu Desnoyers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250210153253.460471-4-gmonaco@redhat.com \
--to=gmonaco@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=shuah@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.