Update version for v4.2.0 release
[qemu.git] / iothread.c
1 /*
2 * Event loop thread
3 *
4 * Copyright Red Hat Inc., 2013
5 *
6 * Authors:
7 * Stefan Hajnoczi <stefanha@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2 or later.
10 * See the COPYING file in the top-level directory.
11 *
12 */
13
14 #include "qemu/osdep.h"
15 #include "qom/object.h"
16 #include "qom/object_interfaces.h"
17 #include "qemu/module.h"
18 #include "block/aio.h"
19 #include "block/block.h"
20 #include "sysemu/iothread.h"
21 #include "qapi/error.h"
22 #include "qapi/qapi-commands-misc.h"
23 #include "qemu/error-report.h"
24 #include "qemu/rcu.h"
25 #include "qemu/main-loop.h"
26
27 typedef ObjectClass IOThreadClass;
28
29 #define IOTHREAD_GET_CLASS(obj) \
30 OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
31 #define IOTHREAD_CLASS(klass) \
32 OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
33
34 #ifdef CONFIG_POSIX
35 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around
36 * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32
37 * workloads.
38 */
39 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL
40 #else
41 #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL
42 #endif
43
44 static __thread IOThread *my_iothread;
45
46 AioContext *qemu_get_current_aio_context(void)
47 {
48 return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
49 }
50
51 static void *iothread_run(void *opaque)
52 {
53 IOThread *iothread = opaque;
54
55 rcu_register_thread();
56 /*
57 * g_main_context_push_thread_default() must be called before anything
58 * in this new thread uses glib.
59 */
60 g_main_context_push_thread_default(iothread->worker_context);
61 my_iothread = iothread;
62 iothread->thread_id = qemu_get_thread_id();
63 qemu_sem_post(&iothread->init_done_sem);
64
65 while (iothread->running) {
66 /*
67 * Note: from functional-wise the g_main_loop_run() below can
68 * already cover the aio_poll() events, but we can't run the
69 * main loop unconditionally because explicit aio_poll() here
70 * is faster than g_main_loop_run() when we do not need the
71 * gcontext at all (e.g., pure block layer iothreads). In
72 * other words, when we want to run the gcontext with the
73 * iothread we need to pay some performance for functionality.
74 */
75 aio_poll(iothread->ctx, true);
76
77 /*
78 * We must check the running state again in case it was
79 * changed in previous aio_poll()
80 */
81 if (iothread->running && atomic_read(&iothread->run_gcontext)) {
82 g_main_loop_run(iothread->main_loop);
83 }
84 }
85
86 g_main_context_pop_thread_default(iothread->worker_context);
87 rcu_unregister_thread();
88 return NULL;
89 }
90
91 /* Runs in iothread_run() thread */
92 static void iothread_stop_bh(void *opaque)
93 {
94 IOThread *iothread = opaque;
95
96 iothread->running = false; /* stop iothread_run() */
97
98 if (iothread->main_loop) {
99 g_main_loop_quit(iothread->main_loop);
100 }
101 }
102
103 void iothread_stop(IOThread *iothread)
104 {
105 if (!iothread->ctx || iothread->stopping) {
106 return;
107 }
108 iothread->stopping = true;
109 aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
110 qemu_thread_join(&iothread->thread);
111 }
112
113 static void iothread_instance_init(Object *obj)
114 {
115 IOThread *iothread = IOTHREAD(obj);
116
117 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
118 iothread->thread_id = -1;
119 qemu_sem_init(&iothread->init_done_sem, 0);
120 /* By default, we don't run gcontext */
121 atomic_set(&iothread->run_gcontext, 0);
122 }
123
124 static void iothread_instance_finalize(Object *obj)
125 {
126 IOThread *iothread = IOTHREAD(obj);
127
128 iothread_stop(iothread);
129
130 /*
131 * Before glib2 2.33.10, there is a glib2 bug that GSource context
132 * pointer may not be cleared even if the context has already been
133 * destroyed (while it should). Here let's free the AIO context
134 * earlier to bypass that glib bug.
135 *
136 * We can remove this comment after the minimum supported glib2
137 * version boosts to 2.33.10. Before that, let's free the
138 * GSources first before destroying any GMainContext.
139 */
140 if (iothread->ctx) {
141 aio_context_unref(iothread->ctx);
142 iothread->ctx = NULL;
143 }
144 if (iothread->worker_context) {
145 g_main_context_unref(iothread->worker_context);
146 iothread->worker_context = NULL;
147 g_main_loop_unref(iothread->main_loop);
148 iothread->main_loop = NULL;
149 }
150 qemu_sem_destroy(&iothread->init_done_sem);
151 }
152
153 static void iothread_init_gcontext(IOThread *iothread)
154 {
155 GSource *source;
156
157 iothread->worker_context = g_main_context_new();
158 source = aio_get_g_source(iothread_get_aio_context(iothread));
159 g_source_attach(source, iothread->worker_context);
160 g_source_unref(source);
161 iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
162 }
163
164 static void iothread_complete(UserCreatable *obj, Error **errp)
165 {
166 Error *local_error = NULL;
167 IOThread *iothread = IOTHREAD(obj);
168 char *name, *thread_name;
169
170 iothread->stopping = false;
171 iothread->running = true;
172 iothread->ctx = aio_context_new(&local_error);
173 if (!iothread->ctx) {
174 error_propagate(errp, local_error);
175 return;
176 }
177
178 /*
179 * Init one GMainContext for the iothread unconditionally, even if
180 * it's not used
181 */
182 iothread_init_gcontext(iothread);
183
184 aio_context_set_poll_params(iothread->ctx,
185 iothread->poll_max_ns,
186 iothread->poll_grow,
187 iothread->poll_shrink,
188 &local_error);
189 if (local_error) {
190 error_propagate(errp, local_error);
191 aio_context_unref(iothread->ctx);
192 iothread->ctx = NULL;
193 return;
194 }
195
196 /* This assumes we are called from a thread with useful CPU affinity for us
197 * to inherit.
198 */
199 name = object_get_canonical_path_component(OBJECT(obj));
200 thread_name = g_strdup_printf("IO %s", name);
201 qemu_thread_create(&iothread->thread, thread_name, iothread_run,
202 iothread, QEMU_THREAD_JOINABLE);
203 g_free(thread_name);
204 g_free(name);
205
206 /* Wait for initialization to complete */
207 while (iothread->thread_id == -1) {
208 qemu_sem_wait(&iothread->init_done_sem);
209 }
210 }
211
212 typedef struct {
213 const char *name;
214 ptrdiff_t offset; /* field's byte offset in IOThread struct */
215 } PollParamInfo;
216
217 static PollParamInfo poll_max_ns_info = {
218 "poll-max-ns", offsetof(IOThread, poll_max_ns),
219 };
220 static PollParamInfo poll_grow_info = {
221 "poll-grow", offsetof(IOThread, poll_grow),
222 };
223 static PollParamInfo poll_shrink_info = {
224 "poll-shrink", offsetof(IOThread, poll_shrink),
225 };
226
227 static void iothread_get_poll_param(Object *obj, Visitor *v,
228 const char *name, void *opaque, Error **errp)
229 {
230 IOThread *iothread = IOTHREAD(obj);
231 PollParamInfo *info = opaque;
232 int64_t *field = (void *)iothread + info->offset;
233
234 visit_type_int64(v, name, field, errp);
235 }
236
237 static void iothread_set_poll_param(Object *obj, Visitor *v,
238 const char *name, void *opaque, Error **errp)
239 {
240 IOThread *iothread = IOTHREAD(obj);
241 PollParamInfo *info = opaque;
242 int64_t *field = (void *)iothread + info->offset;
243 Error *local_err = NULL;
244 int64_t value;
245
246 visit_type_int64(v, name, &value, &local_err);
247 if (local_err) {
248 goto out;
249 }
250
251 if (value < 0) {
252 error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
253 info->name, INT64_MAX);
254 goto out;
255 }
256
257 *field = value;
258
259 if (iothread->ctx) {
260 aio_context_set_poll_params(iothread->ctx,
261 iothread->poll_max_ns,
262 iothread->poll_grow,
263 iothread->poll_shrink,
264 &local_err);
265 }
266
267 out:
268 error_propagate(errp, local_err);
269 }
270
271 static void iothread_class_init(ObjectClass *klass, void *class_data)
272 {
273 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
274 ucc->complete = iothread_complete;
275
276 object_class_property_add(klass, "poll-max-ns", "int",
277 iothread_get_poll_param,
278 iothread_set_poll_param,
279 NULL, &poll_max_ns_info, &error_abort);
280 object_class_property_add(klass, "poll-grow", "int",
281 iothread_get_poll_param,
282 iothread_set_poll_param,
283 NULL, &poll_grow_info, &error_abort);
284 object_class_property_add(klass, "poll-shrink", "int",
285 iothread_get_poll_param,
286 iothread_set_poll_param,
287 NULL, &poll_shrink_info, &error_abort);
288 }
289
290 static const TypeInfo iothread_info = {
291 .name = TYPE_IOTHREAD,
292 .parent = TYPE_OBJECT,
293 .class_init = iothread_class_init,
294 .instance_size = sizeof(IOThread),
295 .instance_init = iothread_instance_init,
296 .instance_finalize = iothread_instance_finalize,
297 .interfaces = (InterfaceInfo[]) {
298 {TYPE_USER_CREATABLE},
299 {}
300 },
301 };
302
303 static void iothread_register_types(void)
304 {
305 type_register_static(&iothread_info);
306 }
307
308 type_init(iothread_register_types)
309
310 char *iothread_get_id(IOThread *iothread)
311 {
312 return object_get_canonical_path_component(OBJECT(iothread));
313 }
314
315 AioContext *iothread_get_aio_context(IOThread *iothread)
316 {
317 return iothread->ctx;
318 }
319
320 static int query_one_iothread(Object *object, void *opaque)
321 {
322 IOThreadInfoList ***prev = opaque;
323 IOThreadInfoList *elem;
324 IOThreadInfo *info;
325 IOThread *iothread;
326
327 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
328 if (!iothread) {
329 return 0;
330 }
331
332 info = g_new0(IOThreadInfo, 1);
333 info->id = iothread_get_id(iothread);
334 info->thread_id = iothread->thread_id;
335 info->poll_max_ns = iothread->poll_max_ns;
336 info->poll_grow = iothread->poll_grow;
337 info->poll_shrink = iothread->poll_shrink;
338
339 elem = g_new0(IOThreadInfoList, 1);
340 elem->value = info;
341 elem->next = NULL;
342
343 **prev = elem;
344 *prev = &elem->next;
345 return 0;
346 }
347
348 IOThreadInfoList *qmp_query_iothreads(Error **errp)
349 {
350 IOThreadInfoList *head = NULL;
351 IOThreadInfoList **prev = &head;
352 Object *container = object_get_objects_root();
353
354 object_child_foreach(container, query_one_iothread, &prev);
355 return head;
356 }
357
358 GMainContext *iothread_get_g_main_context(IOThread *iothread)
359 {
360 atomic_set(&iothread->run_gcontext, 1);
361 aio_notify(iothread->ctx);
362 return iothread->worker_context;
363 }
364
365 IOThread *iothread_create(const char *id, Error **errp)
366 {
367 Object *obj;
368
369 obj = object_new_with_props(TYPE_IOTHREAD,
370 object_get_internal_root(),
371 id, errp, NULL);
372
373 return IOTHREAD(obj);
374 }
375
376 void iothread_destroy(IOThread *iothread)
377 {
378 object_unparent(OBJECT(iothread));
379 }
380
381 /* Lookup IOThread by its id. Only finds user-created objects, not internal
382 * iothread_create() objects. */
383 IOThread *iothread_by_id(const char *id)
384 {
385 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
386 }