Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20200713' into...
[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(errp);
173 if (!iothread->ctx) {
174 return;
175 }
176
177 /*
178 * Init one GMainContext for the iothread unconditionally, even if
179 * it's not used
180 */
181 iothread_init_gcontext(iothread);
182
183 aio_context_set_poll_params(iothread->ctx,
184 iothread->poll_max_ns,
185 iothread->poll_grow,
186 iothread->poll_shrink,
187 &local_error);
188 if (local_error) {
189 error_propagate(errp, local_error);
190 aio_context_unref(iothread->ctx);
191 iothread->ctx = NULL;
192 return;
193 }
194
195 /* This assumes we are called from a thread with useful CPU affinity for us
196 * to inherit.
197 */
198 name = object_get_canonical_path_component(OBJECT(obj));
199 thread_name = g_strdup_printf("IO %s", name);
200 qemu_thread_create(&iothread->thread, thread_name, iothread_run,
201 iothread, QEMU_THREAD_JOINABLE);
202 g_free(thread_name);
203 g_free(name);
204
205 /* Wait for initialization to complete */
206 while (iothread->thread_id == -1) {
207 qemu_sem_wait(&iothread->init_done_sem);
208 }
209 }
210
211 typedef struct {
212 const char *name;
213 ptrdiff_t offset; /* field's byte offset in IOThread struct */
214 } PollParamInfo;
215
216 static PollParamInfo poll_max_ns_info = {
217 "poll-max-ns", offsetof(IOThread, poll_max_ns),
218 };
219 static PollParamInfo poll_grow_info = {
220 "poll-grow", offsetof(IOThread, poll_grow),
221 };
222 static PollParamInfo poll_shrink_info = {
223 "poll-shrink", offsetof(IOThread, poll_shrink),
224 };
225
226 static void iothread_get_poll_param(Object *obj, Visitor *v,
227 const char *name, void *opaque, Error **errp)
228 {
229 IOThread *iothread = IOTHREAD(obj);
230 PollParamInfo *info = opaque;
231 int64_t *field = (void *)iothread + info->offset;
232
233 visit_type_int64(v, name, field, errp);
234 }
235
236 static void iothread_set_poll_param(Object *obj, Visitor *v,
237 const char *name, void *opaque, Error **errp)
238 {
239 IOThread *iothread = IOTHREAD(obj);
240 PollParamInfo *info = opaque;
241 int64_t *field = (void *)iothread + info->offset;
242 int64_t value;
243
244 if (!visit_type_int64(v, name, &value, errp)) {
245 return;
246 }
247
248 if (value < 0) {
249 error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
250 info->name, INT64_MAX);
251 return;
252 }
253
254 *field = value;
255
256 if (iothread->ctx) {
257 aio_context_set_poll_params(iothread->ctx,
258 iothread->poll_max_ns,
259 iothread->poll_grow,
260 iothread->poll_shrink,
261 errp);
262 }
263 }
264
265 static void iothread_class_init(ObjectClass *klass, void *class_data)
266 {
267 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
268 ucc->complete = iothread_complete;
269
270 object_class_property_add(klass, "poll-max-ns", "int",
271 iothread_get_poll_param,
272 iothread_set_poll_param,
273 NULL, &poll_max_ns_info);
274 object_class_property_add(klass, "poll-grow", "int",
275 iothread_get_poll_param,
276 iothread_set_poll_param,
277 NULL, &poll_grow_info);
278 object_class_property_add(klass, "poll-shrink", "int",
279 iothread_get_poll_param,
280 iothread_set_poll_param,
281 NULL, &poll_shrink_info);
282 }
283
284 static const TypeInfo iothread_info = {
285 .name = TYPE_IOTHREAD,
286 .parent = TYPE_OBJECT,
287 .class_init = iothread_class_init,
288 .instance_size = sizeof(IOThread),
289 .instance_init = iothread_instance_init,
290 .instance_finalize = iothread_instance_finalize,
291 .interfaces = (InterfaceInfo[]) {
292 {TYPE_USER_CREATABLE},
293 {}
294 },
295 };
296
297 static void iothread_register_types(void)
298 {
299 type_register_static(&iothread_info);
300 }
301
302 type_init(iothread_register_types)
303
304 char *iothread_get_id(IOThread *iothread)
305 {
306 return object_get_canonical_path_component(OBJECT(iothread));
307 }
308
309 AioContext *iothread_get_aio_context(IOThread *iothread)
310 {
311 return iothread->ctx;
312 }
313
314 static int query_one_iothread(Object *object, void *opaque)
315 {
316 IOThreadInfoList ***prev = opaque;
317 IOThreadInfoList *elem;
318 IOThreadInfo *info;
319 IOThread *iothread;
320
321 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
322 if (!iothread) {
323 return 0;
324 }
325
326 info = g_new0(IOThreadInfo, 1);
327 info->id = iothread_get_id(iothread);
328 info->thread_id = iothread->thread_id;
329 info->poll_max_ns = iothread->poll_max_ns;
330 info->poll_grow = iothread->poll_grow;
331 info->poll_shrink = iothread->poll_shrink;
332
333 elem = g_new0(IOThreadInfoList, 1);
334 elem->value = info;
335 elem->next = NULL;
336
337 **prev = elem;
338 *prev = &elem->next;
339 return 0;
340 }
341
342 IOThreadInfoList *qmp_query_iothreads(Error **errp)
343 {
344 IOThreadInfoList *head = NULL;
345 IOThreadInfoList **prev = &head;
346 Object *container = object_get_objects_root();
347
348 object_child_foreach(container, query_one_iothread, &prev);
349 return head;
350 }
351
352 GMainContext *iothread_get_g_main_context(IOThread *iothread)
353 {
354 atomic_set(&iothread->run_gcontext, 1);
355 aio_notify(iothread->ctx);
356 return iothread->worker_context;
357 }
358
359 IOThread *iothread_create(const char *id, Error **errp)
360 {
361 Object *obj;
362
363 obj = object_new_with_props(TYPE_IOTHREAD,
364 object_get_internal_root(),
365 id, errp, NULL);
366
367 return IOTHREAD(obj);
368 }
369
370 void iothread_destroy(IOThread *iothread)
371 {
372 object_unparent(OBJECT(iothread));
373 }
374
375 /* Lookup IOThread by its id. Only finds user-created objects, not internal
376 * iothread_create() objects. */
377 IOThread *iothread_by_id(const char *id)
378 {
379 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
380 }