#define IOTHREAD_CLASS(klass) \
OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
+#ifdef CONFIG_POSIX
/* Benchmark results from 2016 on NVMe SSD drives show max polling times around
* 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32
* workloads.
*/
#define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL
+#else
+#define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL
+#endif
static __thread IOThread *my_iothread;
IOThread *iothread = opaque;
rcu_register_thread();
-
+ /*
+ * g_main_context_push_thread_default() must be called before anything
+ * in this new thread uses glib.
+ */
+ g_main_context_push_thread_default(iothread->worker_context);
my_iothread = iothread;
- qemu_mutex_lock(&iothread->init_done_lock);
iothread->thread_id = qemu_get_thread_id();
- qemu_cond_signal(&iothread->init_done_cond);
- qemu_mutex_unlock(&iothread->init_done_lock);
+ qemu_sem_post(&iothread->init_done_sem);
while (iothread->running) {
+ /*
+ * Note: from functional-wise the g_main_loop_run() below can
+ * already cover the aio_poll() events, but we can't run the
+ * main loop unconditionally because explicit aio_poll() here
+ * is faster than g_main_loop_run() when we do not need the
+ * gcontext at all (e.g., pure block layer iothreads). In
+ * other words, when we want to run the gcontext with the
+ * iothread we need to pay some performance for functionality.
+ */
aio_poll(iothread->ctx, true);
- if (atomic_read(&iothread->worker_context)) {
- GMainLoop *loop;
-
- g_main_context_push_thread_default(iothread->worker_context);
- iothread->main_loop =
- g_main_loop_new(iothread->worker_context, TRUE);
- loop = iothread->main_loop;
-
+ /*
+ * We must check the running state again in case it was
+ * changed in previous aio_poll()
+ */
+ if (iothread->running && atomic_read(&iothread->run_gcontext)) {
g_main_loop_run(iothread->main_loop);
- iothread->main_loop = NULL;
- g_main_loop_unref(loop);
-
- g_main_context_pop_thread_default(iothread->worker_context);
}
}
+ g_main_context_pop_thread_default(iothread->worker_context);
rcu_unregister_thread();
return NULL;
}
IOThread *iothread = IOTHREAD(obj);
iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
+ iothread->thread_id = -1;
+ qemu_sem_init(&iothread->init_done_sem, 0);
+ /* By default, we don't run gcontext */
+ atomic_set(&iothread->run_gcontext, 0);
}
static void iothread_instance_finalize(Object *obj)
IOThread *iothread = IOTHREAD(obj);
iothread_stop(iothread);
+
+ /*
+ * Before glib2 2.33.10, there is a glib2 bug that GSource context
+ * pointer may not be cleared even if the context has already been
+ * destroyed (while it should). Here let's free the AIO context
+ * earlier to bypass that glib bug.
+ *
+ * We can remove this comment after the minimum supported glib2
+ * version boosts to 2.33.10. Before that, let's free the
+ * GSources first before destroying any GMainContext.
+ */
+ if (iothread->ctx) {
+ aio_context_unref(iothread->ctx);
+ iothread->ctx = NULL;
+ }
if (iothread->worker_context) {
g_main_context_unref(iothread->worker_context);
iothread->worker_context = NULL;
+ g_main_loop_unref(iothread->main_loop);
+ iothread->main_loop = NULL;
}
- qemu_cond_destroy(&iothread->init_done_cond);
- qemu_mutex_destroy(&iothread->init_done_lock);
- if (!iothread->ctx) {
- return;
- }
- aio_context_unref(iothread->ctx);
+ qemu_sem_destroy(&iothread->init_done_sem);
+}
+
+static void iothread_init_gcontext(IOThread *iothread)
+{
+ GSource *source;
+
+ iothread->worker_context = g_main_context_new();
+ source = aio_get_g_source(iothread_get_aio_context(iothread));
+ g_source_attach(source, iothread->worker_context);
+ g_source_unref(source);
+ iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
}
static void iothread_complete(UserCreatable *obj, Error **errp)
iothread->stopping = false;
iothread->running = true;
- iothread->thread_id = -1;
iothread->ctx = aio_context_new(&local_error);
if (!iothread->ctx) {
error_propagate(errp, local_error);
return;
}
+ /*
+ * Init one GMainContext for the iothread unconditionally, even if
+ * it's not used
+ */
+ iothread_init_gcontext(iothread);
+
aio_context_set_poll_params(iothread->ctx,
iothread->poll_max_ns,
iothread->poll_grow,
return;
}
- qemu_mutex_init(&iothread->init_done_lock);
- qemu_cond_init(&iothread->init_done_cond);
- iothread->once = (GOnce) G_ONCE_INIT;
-
/* This assumes we are called from a thread with useful CPU affinity for us
* to inherit.
*/
g_free(name);
/* Wait for initialization to complete */
- qemu_mutex_lock(&iothread->init_done_lock);
while (iothread->thread_id == -1) {
- qemu_cond_wait(&iothread->init_done_cond,
- &iothread->init_done_lock);
+ qemu_sem_wait(&iothread->init_done_sem);
}
- qemu_mutex_unlock(&iothread->init_done_lock);
}
typedef struct {
return head;
}
-static gpointer iothread_g_main_context_init(gpointer opaque)
-{
- AioContext *ctx;
- IOThread *iothread = opaque;
- GSource *source;
-
- iothread->worker_context = g_main_context_new();
-
- ctx = iothread_get_aio_context(iothread);
- source = aio_get_g_source(ctx);
- g_source_attach(source, iothread->worker_context);
- g_source_unref(source);
-
- aio_notify(iothread->ctx);
- return NULL;
-}
-
GMainContext *iothread_get_g_main_context(IOThread *iothread)
{
- g_once(&iothread->once, iothread_g_main_context_init, iothread);
-
+ atomic_set(&iothread->run_gcontext, 1);
+ aio_notify(iothread->ctx);
return iothread->worker_context;
}
projects / qemu.git / blobdiff