diff options
Diffstat (limited to 'iothread.c')
| -rw-r--r-- | iothread.c | 386 |
1 files changed, 386 insertions, 0 deletions
diff --git a/iothread.c b/iothread.c new file mode 100644 index 000000000..7130be58e --- /dev/null +++ b/iothread.c @@ -0,0 +1,386 @@ +/* + * Event loop thread + * + * Copyright Red Hat Inc., 2013 + * + * 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; + +#define IOTHREAD_GET_CLASS(obj) \ + OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD) +#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; + + 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; + 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 && atomic_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 */ + 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_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) +{ + Error *local_error = NULL; + IOThread *iothread = IOTHREAD(obj); + char *name, *thread_name; + + iothread->stopping = false; + iothread->running = true; + 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, + iothread->poll_shrink, + &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. + */ + name = object_get_canonical_path_component(OBJECT(obj)); + thread_name = g_strdup_printf("IO %s", name); + qemu_thread_create(&iothread->thread, thread_name, iothread_run, + iothread, QEMU_THREAD_JOINABLE); + g_free(thread_name); + g_free(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 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 = { + .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 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 ***prev = opaque; + IOThreadInfoList *elem; + 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; + + elem = g_new0(IOThreadInfoList, 1); + elem->value = info; + elem->next = NULL; + + **prev = elem; + *prev = &elem->next; + 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) +{ + atomic_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)); +} |