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[Qemu-devel] [PATCH 08/11] test-aio-multithread: add performance compari
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 08/11] test-aio-multithread: add performance comparison with thread-based mutexes |
Date: |
Fri, 15 Apr 2016 13:32:03 +0200 |
Add two implementations of the same benchmark as the previous patch,
but using pthreads. One uses a normal QemuMutex, the other is Linux
only and implements a fair mutex based on MCS locks and futexes.
This shows that the slower performance of the 5-thread case is due to
the fairness of CoMutex, rather than to coroutines. If fairness does
not matter, as is the case with two threads, CoMutex can actually be
faster than pthreads.
Signed-off-by: Paolo Bonzini <address@hidden>
---
tests/test-aio-multithread.c | 152 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 152 insertions(+)
diff --git a/tests/test-aio-multithread.c b/tests/test-aio-multithread.c
index 18b3548..d7bc1bf 100644
--- a/tests/test-aio-multithread.c
+++ b/tests/test-aio-multithread.c
@@ -279,6 +279,150 @@ static void test_multi_co_mutex_2_30(void)
test_multi_co_mutex(2, 30);
}
+/* Same test with fair mutexes, for performance comparison. */
+
+#ifdef CONFIG_LINUX
+#include "qemu/futex.h"
+
+/* The nodes for the mutex reside in this structure (on which we try to avoid
+ * false sharing). The head of the mutex is in the "mutex_head" variable.
+ */
+static struct {
+ int next, locked;
+ int padding[14];
+} nodes[NUM_CONTEXTS] __attribute__((__aligned__(64)));
+
+static int mutex_head = -1;
+
+static void mcs_mutex_lock(void)
+{
+ int prev;
+
+ nodes[id].next = -1;
+ nodes[id].locked = 1;
+ prev = atomic_xchg(&mutex_head, id);
+ if (prev != -1) {
+ atomic_set(&nodes[prev].next, id);
+ futex_wait(&nodes[id].locked, 1);
+ }
+}
+
+static void mcs_mutex_unlock(void)
+{
+ int next;
+ if (nodes[id].next == -1) {
+ if (atomic_read(&mutex_head) == id &&
+ atomic_cmpxchg(&mutex_head, id, -1) == id) {
+ /* Last item in the list, exit. */
+ return;
+ }
+ while (atomic_read(&nodes[id].next) == -1) {
+ /* Spin... */
+ }
+ }
+
+ /* Wake up the next in line. */
+ next = nodes[id].next;
+ nodes[next].locked = 0;
+ futex_wake(&nodes[next].locked, 1);
+}
+
+static void test_multi_fair_mutex_entry(void *opaque)
+{
+ while (!atomic_mb_read(&now_stopping)) {
+ mcs_mutex_lock();
+ counter++;
+ mcs_mutex_unlock();
+ atomic_inc(&atomic_counter);
+ }
+
+}
+
+static void test_multi_fair_mutex(int threads, int seconds)
+{
+ int i;
+
+ assert(mutex_head == -1);
+ counter = 0;
+ atomic_counter = 0;
+ now_stopping = false;
+
+ create_aio_contexts();
+ assert(threads <= NUM_CONTEXTS);
+ for (i = 0; i < threads; i++) {
+ Coroutine *co1 = qemu_coroutine_create(test_multi_fair_mutex_entry);
+ aio_co_schedule(ctx[i], co1);
+ }
+
+ g_usleep(seconds * 1000000);
+
+ atomic_mb_set(&now_stopping, true);
+ join_aio_contexts();
+ g_test_message("%d iterations/second\n", counter / seconds);
+ g_assert_cmpint(counter, ==, atomic_counter);
+}
+
+static void test_multi_fair_mutex_1(void)
+{
+ test_multi_fair_mutex(NUM_CONTEXTS, 1);
+}
+
+static void test_multi_fair_mutex_10(void)
+{
+ test_multi_fair_mutex(NUM_CONTEXTS, 10);
+}
+#endif
+
+/* Same test with pthread mutexes, for performance comparison and
+ * portability. */
+
+static QemuMutex mutex;
+
+static void test_multi_mutex_entry(void *opaque)
+{
+ while (!atomic_mb_read(&now_stopping)) {
+ qemu_mutex_lock(&mutex);
+ counter++;
+ qemu_mutex_unlock(&mutex);
+ atomic_inc(&atomic_counter);
+ }
+
+}
+
+static void test_multi_mutex(int threads, int seconds)
+{
+ int i;
+
+ qemu_mutex_init(&mutex);
+ counter = 0;
+ atomic_counter = 0;
+ now_stopping = false;
+
+ create_aio_contexts();
+ assert(threads <= NUM_CONTEXTS);
+ for (i = 0; i < threads; i++) {
+ Coroutine *co1 = qemu_coroutine_create(test_multi_mutex_entry);
+ aio_co_schedule(ctx[i], co1);
+ }
+
+ g_usleep(seconds * 1000000);
+
+ atomic_mb_set(&now_stopping, true);
+ join_aio_contexts();
+ g_test_message("%d iterations/second\n", counter / seconds);
+ g_assert_cmpint(counter, ==, atomic_counter);
+}
+
+static void test_multi_mutex_1(void)
+{
+ test_multi_mutex(NUM_CONTEXTS, 1);
+}
+
+static void test_multi_mutex_10(void)
+{
+ test_multi_mutex(NUM_CONTEXTS, 10);
+}
+
/* End of tests. */
int main(int argc, char **argv)
@@ -291,10 +435,18 @@ int main(int argc, char **argv)
g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_1);
g_test_add_func("/aio/multi/mutex", test_multi_co_mutex_1);
g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_3);
+#ifdef CONFIG_LINUX
+ g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_1);
+#endif
+ g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_1);
} else {
g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_10);
g_test_add_func("/aio/multi/mutex", test_multi_co_mutex_10);
g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_30);
+#ifdef CONFIG_LINUX
+ g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_10);
+#endif
+ g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_10);
}
return g_test_run();
}
--
2.5.5
- [Qemu-devel] [PATCH 05/11] coroutine-lock: reschedule coroutine on the AioContext it was running on, (continued)
- [Qemu-devel] [PATCH 05/11] coroutine-lock: reschedule coroutine on the AioContext it was running on, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 06/11] coroutine-lock: make CoMutex thread-safe, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 02/11] throttle-groups: restart throttled requests from coroutine context, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 04/11] aio: introduce aio_co_schedule, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 07/11] coroutine-lock: add limited spinning to CoMutex, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 10/11] coroutine-lock: add mutex argument to CoQueue APIs, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 08/11] test-aio-multithread: add performance comparison with thread-based mutexes,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 09/11] coroutine-lock: place CoMutex before CoQueue in header, Paolo Bonzini, 2016/04/15
- [Qemu-devel] [PATCH 11/11] coroutine-lock: make CoRwlock thread-safe and fair, Paolo Bonzini, 2016/04/15
- Re: [Qemu-devel] [RFC PATCH resend 00/11] Make CoMutex/CoQueue/CoRwlock thread-safe, Stefan Hajnoczi, 2016/04/26