X-Git-Url: https://repo.jachan.dev/qemu.git/blobdiff_plain/8212ff86f4405b6128d89dd1d97ff2d6cfcf9842..e18a58b4e3aa355a9b6eef1f39a980a4f18f1294:/iothread.c

diff --git a/iothread.c b/iothread.c
index fb08a60b4b..aff1281257 100644
--- a/iothread.c
+++ b/iothread.c
@@ -16,10 +16,13 @@
 #include "qom/object_interfaces.h"
 #include "qemu/module.h"
 #include "block/aio.h"
+#include "block/block.h"
 #include "sysemu/iothread.h"
-#include "qmp-commands.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-misc.h"
 #include "qemu/error-report.h"
 #include "qemu/rcu.h"
+#include "qemu/main-loop.h"
 
 typedef ObjectClass IOThreadClass;
 
@@ -28,54 +31,112 @@ typedef ObjectClass IOThreadClass;
 #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;
+
+AioContext *qemu_get_current_aio_context(void)
+{
+    return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
+}
+
 static void *iothread_run(void *opaque)
 {
     IOThread *iothread = opaque;
-    bool blocking;
 
     rcu_register_thread();
 
+    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);
 
-    while (!iothread->stopping) {
-        aio_context_acquire(iothread->ctx);
-        blocking = true;
-        while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
-            /* Progress was made, keep going */
-            blocking = false;
+    while (iothread->running) {
+        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;
+
+            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);
         }
-        aio_context_release(iothread->ctx);
     }
 
     rcu_unregister_thread();
     return NULL;
 }
 
-static int iothread_stop(Object *object, void *opaque)
+/* Runs in iothread_run() thread */
+static void iothread_stop_bh(void *opaque)
 {
-    IOThread *iothread;
+    IOThread *iothread = opaque;
 
-    iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
-    if (!iothread || !iothread->ctx) {
-        return 0;
+    iothread->running = false; /* stop iothread_run() */
+
+    if (iothread->main_loop) {
+        g_main_loop_quit(iothread->main_loop);
+    }
+}
+
+void iothread_stop(IOThread *iothread)
+{
+    if (!iothread->ctx || iothread->stopping) {
+        return;
     }
     iothread->stopping = true;
-    aio_notify(iothread->ctx);
+    aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
     qemu_thread_join(&iothread->thread);
-    return 0;
+}
+
+static void iothread_instance_init(Object *obj)
+{
+    IOThread *iothread = IOTHREAD(obj);
+
+    iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
 }
 
 static void iothread_instance_finalize(Object *obj)
 {
     IOThread *iothread = IOTHREAD(obj);
 
-    iothread_stop(obj, NULL);
+    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;
+    }
     qemu_cond_destroy(&iothread->init_done_cond);
     qemu_mutex_destroy(&iothread->init_done_lock);
-    aio_context_unref(iothread->ctx);
 }
 
 static void iothread_complete(UserCreatable *obj, Error **errp)
@@ -85,6 +146,7 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
     char *name, *thread_name;
 
     iothread->stopping = false;
+    iothread->running = true;
     iothread->thread_id = -1;
     iothread->ctx = aio_context_new(&local_error);
     if (!iothread->ctx) {
@@ -92,8 +154,21 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
         return;
     }
 
+    aio_context_set_poll_params(iothread->ctx,
+                                iothread->poll_max_ns,
+                                iothread->poll_grow,
+                                iothread->poll_shrink,
+                                &local_error);
+    if (local_error) {
+        error_propagate(errp, local_error);
+        aio_context_unref(iothread->ctx);
+        iothread->ctx = NULL;
+        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.
@@ -114,10 +189,82 @@ static void iothread_complete(UserCreatable *obj, Error **errp)
     qemu_mutex_unlock(&iothread->init_done_lock);
 }
 
+typedef struct {
+    const char *name;
+    ptrdiff_t offset; /* field's byte offset in IOThread struct */
+} PollParamInfo;
+
+static PollParamInfo poll_max_ns_info = {
+    "poll-max-ns", offsetof(IOThread, poll_max_ns),
+};
+static PollParamInfo poll_grow_info = {
+    "poll-grow", offsetof(IOThread, poll_grow),
+};
+static PollParamInfo poll_shrink_info = {
+    "poll-shrink", offsetof(IOThread, poll_shrink),
+};
+
+static void iothread_get_poll_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    IOThread *iothread = IOTHREAD(obj);
+    PollParamInfo *info = opaque;
+    int64_t *field = (void *)iothread + info->offset;
+
+    visit_type_int64(v, name, field, errp);
+}
+
+static void iothread_set_poll_param(Object *obj, Visitor *v,
+        const char *name, void *opaque, Error **errp)
+{
+    IOThread *iothread = IOTHREAD(obj);
+    PollParamInfo *info = opaque;
+    int64_t *field = (void *)iothread + info->offset;
+    Error *local_err = NULL;
+    int64_t value;
+
+    visit_type_int64(v, name, &value, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
+    if (value < 0) {
+        error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
+                   info->name, INT64_MAX);
+        goto out;
+    }
+
+    *field = value;
+
+    if (iothread->ctx) {
+        aio_context_set_poll_params(iothread->ctx,
+                                    iothread->poll_max_ns,
+                                    iothread->poll_grow,
+                                    iothread->poll_shrink,
+                                    &local_err);
+    }
+
+out:
+    error_propagate(errp, local_err);
+}
+
 static void iothread_class_init(ObjectClass *klass, void *class_data)
 {
     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
     ucc->complete = iothread_complete;
+
+    object_class_property_add(klass, "poll-max-ns", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_max_ns_info, &error_abort);
+    object_class_property_add(klass, "poll-grow", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_grow_info, &error_abort);
+    object_class_property_add(klass, "poll-shrink", "int",
+                              iothread_get_poll_param,
+                              iothread_set_poll_param,
+                              NULL, &poll_shrink_info, &error_abort);
 }
 
 static const TypeInfo iothread_info = {
@@ -125,6 +272,7 @@ static const TypeInfo iothread_info = {
     .parent = TYPE_OBJECT,
     .class_init = iothread_class_init,
     .instance_size = sizeof(IOThread),
+    .instance_init = iothread_instance_init,
     .instance_finalize = iothread_instance_finalize,
     .interfaces = (InterfaceInfo[]) {
         {TYPE_USER_CREATABLE},
@@ -164,6 +312,9 @@ static int query_one_iothread(Object *object, void *opaque)
     info = g_new0(IOThreadInfo, 1);
     info->id = iothread_get_id(iothread);
     info->thread_id = iothread->thread_id;
+    info->poll_max_ns = iothread->poll_max_ns;
+    info->poll_grow = iothread->poll_grow;
+    info->poll_shrink = iothread->poll_shrink;
 
     elem = g_new0(IOThreadInfoList, 1);
     elem->value = info;
@@ -184,9 +335,49 @@ IOThreadInfoList *qmp_query_iothreads(Error **errp)
     return head;
 }
 
-void iothread_stop_all(void)
+static gpointer iothread_g_main_context_init(gpointer opaque)
 {
-    Object *container = object_get_objects_root();
+    AioContext *ctx;
+    IOThread *iothread = opaque;
+    GSource *source;
 
-    object_child_foreach(container, iothread_stop, NULL);
+    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);
+
+    return iothread->worker_context;
+}
+
+IOThread *iothread_create(const char *id, Error **errp)
+{
+    Object *obj;
+
+    obj = object_new_with_props(TYPE_IOTHREAD,
+                                object_get_internal_root(),
+                                id, errp, NULL);
+
+    return IOTHREAD(obj);
+}
+
+void iothread_destroy(IOThread *iothread)
+{
+    object_unparent(OBJECT(iothread));
+}
+
+/* Lookup IOThread by its id.  Only finds user-created objects, not internal
+ * iothread_create() objects. */
+IOThread *iothread_by_id(const char *id)
+{
+    return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
 }