/* * 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/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" typedef ObjectClass IOThreadClass; DECLARE_CLASS_CHECKERS(IOThreadClass, IOTHREAD, 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 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) { 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_set_aio_context_params(IOThread *iothread, Error **errp) { ERRP_GUARD(); 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->aio_max_batch, errp); } static void iothread_complete(UserCreatable *obj, Error **errp) { Error *local_error = NULL; IOThread *iothread = IOTHREAD(obj); char *thread_name; iothread->stopping = false; iothread->running = true; iothread->ctx = aio_context_new(errp); if (!iothread->ctx) { return; } /* * Init one GMainContext for the iothread unconditionally, even if * it's not used */ iothread_init_gcontext(iothread); iothread_set_aio_context_params(iothread, &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. */ thread_name = g_strdup_printf("IO %s", object_get_canonical_path_component(OBJECT(obj))); qemu_thread_create(&iothread->thread, thread_name, iothread_run, iothread, QEMU_THREAD_JOINABLE); g_free(thread_name); /* 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 */ } 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 PollParamInfo aio_max_batch_info = { "aio-max-batch", offsetof(IOThread, aio_max_batch), }; static void iothread_get_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 bool iothread_set_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; 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) { iothread_get_param(obj, v, name, opaque, errp); } static void iothread_set_poll_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) { IOThread *iothread = IOTHREAD(obj); if (!iothread_set_param(obj, v, name, opaque, 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_get_aio_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) { iothread_get_param(obj, v, name, opaque, errp); } static void iothread_set_aio_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) { IOThread *iothread = IOTHREAD(obj); if (!iothread_set_param(obj, v, name, opaque, errp)) { return; } if (iothread->ctx) { aio_context_set_aio_params(iothread->ctx, iothread->aio_max_batch, errp); } } 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); 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); object_class_property_add(klass, "aio-max-batch", "int", iothread_get_aio_param, iothread_set_aio_param, NULL, &aio_max_batch_info); } static const TypeInfo iothread_info = { .name = TYPE_IOTHREAD, .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}, {} }, }; 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->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() ? false : true; }