| /* |
| * Event loop thread |
| * |
| * Copyright Red Hat Inc., 2013, 2020 |
| * |
| * Authors: |
| * Stefan Hajnoczi <stefanha@redhat.com> |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| * See the COPYING file in the top-level directory. |
| * |
| */ |
| |
| #include "qemu/osdep.h" |
| #include "qom/object.h" |
| #include "qom/object_interfaces.h" |
| #include "qemu/module.h" |
| #include "block/aio.h" |
| #include "block/block.h" |
| #include "sysemu/event-loop-base.h" |
| #include "sysemu/iothread.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" |
| |
| |
| #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 void *iothread_run(void *opaque) |
| { |
| 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); |
| qemu_set_current_aio_context(iothread->ctx); |
| iothread->thread_id = qemu_get_thread_id(); |
| 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); |
| |
| /* |
| * We must check the running state again in case it was |
| * changed in previous aio_poll() |
| */ |
| if (iothread->running && qatomic_read(&iothread->run_gcontext)) { |
| g_main_loop_run(iothread->main_loop); |
| } |
| } |
| |
| g_main_context_pop_thread_default(iothread->worker_context); |
| rcu_unregister_thread(); |
| return NULL; |
| } |
| |
| /* Runs in iothread_run() thread */ |
| static void iothread_stop_bh(void *opaque) |
| { |
| IOThread *iothread = opaque; |
| |
| 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_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); |
| qemu_thread_join(&iothread->thread); |
| } |
| |
| static void iothread_instance_init(Object *obj) |
| { |
| 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 */ |
| qatomic_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_sem_destroy(&iothread->init_done_sem); |
| } |
| |
| static void iothread_init_gcontext(IOThread *iothread, const char *thread_name) |
| { |
| GSource *source; |
| g_autofree char *name = g_strdup_printf("%s aio-context", thread_name); |
| |
| iothread->worker_context = g_main_context_new(); |
| source = aio_get_g_source(iothread_get_aio_context(iothread)); |
| g_source_set_name(source, name); |
| 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_set_aio_context_params(EventLoopBase *base, Error **errp) |
| { |
| ERRP_GUARD(); |
| IOThread *iothread = IOTHREAD(base); |
| |
| if (!iothread->ctx) { |
| return; |
| } |
| |
| aio_context_set_poll_params(iothread->ctx, |
| iothread->poll_max_ns, |
| iothread->poll_grow, |
| iothread->poll_shrink, |
| errp); |
| if (*errp) { |
| return; |
| } |
| |
| aio_context_set_aio_params(iothread->ctx, |
| iothread->parent_obj.aio_max_batch); |
| |
| aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min, |
| base->thread_pool_max, errp); |
| } |
| |
| |
| static void iothread_init(EventLoopBase *base, Error **errp) |
| { |
| Error *local_error = NULL; |
| IOThread *iothread = IOTHREAD(base); |
| g_autofree char *thread_name = NULL; |
| |
| iothread->stopping = false; |
| iothread->running = true; |
| iothread->ctx = aio_context_new(errp); |
| if (!iothread->ctx) { |
| return; |
| } |
| |
| thread_name = g_strdup_printf("IO %s", |
| object_get_canonical_path_component(OBJECT(base))); |
| |
| /* |
| * Init one GMainContext for the iothread unconditionally, even if |
| * it's not used |
| */ |
| iothread_init_gcontext(iothread, thread_name); |
| |
| iothread_set_aio_context_params(base, &local_error); |
| if (local_error) { |
| error_propagate(errp, local_error); |
| aio_context_unref(iothread->ctx); |
| iothread->ctx = NULL; |
| return; |
| } |
| |
| /* This assumes we are called from a thread with useful CPU affinity for us |
| * to inherit. |
| */ |
| qemu_thread_create(&iothread->thread, thread_name, iothread_run, |
| iothread, QEMU_THREAD_JOINABLE); |
| |
| /* Wait for initialization to complete */ |
| while (iothread->thread_id == -1) { |
| qemu_sem_wait(&iothread->init_done_sem); |
| } |
| } |
| |
| typedef struct { |
| const char *name; |
| ptrdiff_t offset; /* field's byte offset in IOThread struct */ |
| } IOThreadParamInfo; |
| |
| static IOThreadParamInfo poll_max_ns_info = { |
| "poll-max-ns", offsetof(IOThread, poll_max_ns), |
| }; |
| static IOThreadParamInfo poll_grow_info = { |
| "poll-grow", offsetof(IOThread, poll_grow), |
| }; |
| static IOThreadParamInfo poll_shrink_info = { |
| "poll-shrink", offsetof(IOThread, poll_shrink), |
| }; |
| |
| static void iothread_get_param(Object *obj, Visitor *v, |
| const char *name, IOThreadParamInfo *info, Error **errp) |
| { |
| IOThread *iothread = IOTHREAD(obj); |
| int64_t *field = (void *)iothread + info->offset; |
| |
| visit_type_int64(v, name, field, errp); |
| } |
| |
| static bool iothread_set_param(Object *obj, Visitor *v, |
| const char *name, IOThreadParamInfo *info, Error **errp) |
| { |
| IOThread *iothread = IOTHREAD(obj); |
| int64_t *field = (void *)iothread + info->offset; |
| int64_t value; |
| |
| if (!visit_type_int64(v, name, &value, errp)) { |
| return false; |
| } |
| |
| if (value < 0) { |
| error_setg(errp, "%s value must be in range [0, %" PRId64 "]", |
| info->name, INT64_MAX); |
| return false; |
| } |
| |
| *field = value; |
| |
| return true; |
| } |
| |
| static void iothread_get_poll_param(Object *obj, Visitor *v, |
| const char *name, void *opaque, Error **errp) |
| { |
| IOThreadParamInfo *info = opaque; |
| |
| iothread_get_param(obj, v, name, info, errp); |
| } |
| |
| static void iothread_set_poll_param(Object *obj, Visitor *v, |
| const char *name, void *opaque, Error **errp) |
| { |
| IOThread *iothread = IOTHREAD(obj); |
| IOThreadParamInfo *info = opaque; |
| |
| if (!iothread_set_param(obj, v, name, info, errp)) { |
| return; |
| } |
| |
| if (iothread->ctx) { |
| aio_context_set_poll_params(iothread->ctx, |
| iothread->poll_max_ns, |
| iothread->poll_grow, |
| iothread->poll_shrink, |
| errp); |
| } |
| } |
| |
| static void iothread_class_init(ObjectClass *klass, void *class_data) |
| { |
| EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass); |
| |
| bc->init = iothread_init; |
| bc->update_params = iothread_set_aio_context_params; |
| |
| object_class_property_add(klass, "poll-max-ns", "int", |
| iothread_get_poll_param, |
| iothread_set_poll_param, |
| NULL, &poll_max_ns_info); |
| object_class_property_add(klass, "poll-grow", "int", |
| iothread_get_poll_param, |
| iothread_set_poll_param, |
| NULL, &poll_grow_info); |
| object_class_property_add(klass, "poll-shrink", "int", |
| iothread_get_poll_param, |
| iothread_set_poll_param, |
| NULL, &poll_shrink_info); |
| } |
| |
| static const TypeInfo iothread_info = { |
| .name = TYPE_IOTHREAD, |
| .parent = TYPE_EVENT_LOOP_BASE, |
| .class_init = iothread_class_init, |
| .instance_size = sizeof(IOThread), |
| .instance_init = iothread_instance_init, |
| .instance_finalize = iothread_instance_finalize, |
| }; |
| |
| static void iothread_register_types(void) |
| { |
| type_register_static(&iothread_info); |
| } |
| |
| type_init(iothread_register_types) |
| |
| char *iothread_get_id(IOThread *iothread) |
| { |
| return g_strdup(object_get_canonical_path_component(OBJECT(iothread))); |
| } |
| |
| AioContext *iothread_get_aio_context(IOThread *iothread) |
| { |
| return iothread->ctx; |
| } |
| |
| static int query_one_iothread(Object *object, void *opaque) |
| { |
| IOThreadInfoList ***tail = opaque; |
| IOThreadInfo *info; |
| IOThread *iothread; |
| |
| iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); |
| if (!iothread) { |
| return 0; |
| } |
| |
| 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; |
| info->aio_max_batch = iothread->parent_obj.aio_max_batch; |
| |
| QAPI_LIST_APPEND(*tail, info); |
| return 0; |
| } |
| |
| IOThreadInfoList *qmp_query_iothreads(Error **errp) |
| { |
| IOThreadInfoList *head = NULL; |
| IOThreadInfoList **prev = &head; |
| Object *container = object_get_objects_root(); |
| |
| object_child_foreach(container, query_one_iothread, &prev); |
| return head; |
| } |
| |
| GMainContext *iothread_get_g_main_context(IOThread *iothread) |
| { |
| qatomic_set(&iothread->run_gcontext, 1); |
| aio_notify(iothread->ctx); |
| 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)); |
| } |
| |
| bool qemu_in_iothread(void) |
| { |
| return qemu_get_current_aio_context() != qemu_get_aio_context(); |
| } |
