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1 | /* | |
2 | * Event loop thread | |
3 | * | |
4 | * Copyright Red Hat Inc., 2013, 2020 | |
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 | DECLARE_CLASS_CHECKERS(IOThreadClass, IOTHREAD, | |
30 | TYPE_IOTHREAD) | |
31 | ||
32 | #ifdef CONFIG_POSIX | |
33 | /* Benchmark results from 2016 on NVMe SSD drives show max polling times around | |
34 | * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32 | |
35 | * workloads. | |
36 | */ | |
37 | #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL | |
38 | #else | |
39 | #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL | |
40 | #endif | |
41 | ||
42 | static void *iothread_run(void *opaque) | |
43 | { | |
44 | IOThread *iothread = opaque; | |
45 | ||
46 | rcu_register_thread(); | |
47 | /* | |
48 | * g_main_context_push_thread_default() must be called before anything | |
49 | * in this new thread uses glib. | |
50 | */ | |
51 | g_main_context_push_thread_default(iothread->worker_context); | |
52 | qemu_set_current_aio_context(iothread->ctx); | |
53 | iothread->thread_id = qemu_get_thread_id(); | |
54 | qemu_sem_post(&iothread->init_done_sem); | |
55 | ||
56 | while (iothread->running) { | |
57 | /* | |
58 | * Note: from functional-wise the g_main_loop_run() below can | |
59 | * already cover the aio_poll() events, but we can't run the | |
60 | * main loop unconditionally because explicit aio_poll() here | |
61 | * is faster than g_main_loop_run() when we do not need the | |
62 | * gcontext at all (e.g., pure block layer iothreads). In | |
63 | * other words, when we want to run the gcontext with the | |
64 | * iothread we need to pay some performance for functionality. | |
65 | */ | |
66 | aio_poll(iothread->ctx, true); | |
67 | ||
68 | /* | |
69 | * We must check the running state again in case it was | |
70 | * changed in previous aio_poll() | |
71 | */ | |
72 | if (iothread->running && qatomic_read(&iothread->run_gcontext)) { | |
73 | g_main_loop_run(iothread->main_loop); | |
74 | } | |
75 | } | |
76 | ||
77 | g_main_context_pop_thread_default(iothread->worker_context); | |
78 | rcu_unregister_thread(); | |
79 | return NULL; | |
80 | } | |
81 | ||
82 | /* Runs in iothread_run() thread */ | |
83 | static void iothread_stop_bh(void *opaque) | |
84 | { | |
85 | IOThread *iothread = opaque; | |
86 | ||
87 | iothread->running = false; /* stop iothread_run() */ | |
88 | ||
89 | if (iothread->main_loop) { | |
90 | g_main_loop_quit(iothread->main_loop); | |
91 | } | |
92 | } | |
93 | ||
94 | void iothread_stop(IOThread *iothread) | |
95 | { | |
96 | if (!iothread->ctx || iothread->stopping) { | |
97 | return; | |
98 | } | |
99 | iothread->stopping = true; | |
100 | aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); | |
101 | qemu_thread_join(&iothread->thread); | |
102 | } | |
103 | ||
104 | static void iothread_instance_init(Object *obj) | |
105 | { | |
106 | IOThread *iothread = IOTHREAD(obj); | |
107 | ||
108 | iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT; | |
109 | iothread->thread_id = -1; | |
110 | qemu_sem_init(&iothread->init_done_sem, 0); | |
111 | /* By default, we don't run gcontext */ | |
112 | qatomic_set(&iothread->run_gcontext, 0); | |
113 | } | |
114 | ||
115 | static void iothread_instance_finalize(Object *obj) | |
116 | { | |
117 | IOThread *iothread = IOTHREAD(obj); | |
118 | ||
119 | iothread_stop(iothread); | |
120 | ||
121 | /* | |
122 | * Before glib2 2.33.10, there is a glib2 bug that GSource context | |
123 | * pointer may not be cleared even if the context has already been | |
124 | * destroyed (while it should). Here let's free the AIO context | |
125 | * earlier to bypass that glib bug. | |
126 | * | |
127 | * We can remove this comment after the minimum supported glib2 | |
128 | * version boosts to 2.33.10. Before that, let's free the | |
129 | * GSources first before destroying any GMainContext. | |
130 | */ | |
131 | if (iothread->ctx) { | |
132 | aio_context_unref(iothread->ctx); | |
133 | iothread->ctx = NULL; | |
134 | } | |
135 | if (iothread->worker_context) { | |
136 | g_main_context_unref(iothread->worker_context); | |
137 | iothread->worker_context = NULL; | |
138 | g_main_loop_unref(iothread->main_loop); | |
139 | iothread->main_loop = NULL; | |
140 | } | |
141 | qemu_sem_destroy(&iothread->init_done_sem); | |
142 | } | |
143 | ||
144 | static void iothread_init_gcontext(IOThread *iothread) | |
145 | { | |
146 | GSource *source; | |
147 | ||
148 | iothread->worker_context = g_main_context_new(); | |
149 | source = aio_get_g_source(iothread_get_aio_context(iothread)); | |
150 | g_source_attach(source, iothread->worker_context); | |
151 | g_source_unref(source); | |
152 | iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE); | |
153 | } | |
154 | ||
155 | static void iothread_set_aio_context_params(IOThread *iothread, Error **errp) | |
156 | { | |
157 | ERRP_GUARD(); | |
158 | ||
159 | aio_context_set_poll_params(iothread->ctx, | |
160 | iothread->poll_max_ns, | |
161 | iothread->poll_grow, | |
162 | iothread->poll_shrink, | |
163 | errp); | |
164 | if (*errp) { | |
165 | return; | |
166 | } | |
167 | ||
168 | aio_context_set_aio_params(iothread->ctx, | |
169 | iothread->aio_max_batch, | |
170 | errp); | |
171 | } | |
172 | ||
173 | static void iothread_complete(UserCreatable *obj, Error **errp) | |
174 | { | |
175 | Error *local_error = NULL; | |
176 | IOThread *iothread = IOTHREAD(obj); | |
177 | char *thread_name; | |
178 | ||
179 | iothread->stopping = false; | |
180 | iothread->running = true; | |
181 | iothread->ctx = aio_context_new(errp); | |
182 | if (!iothread->ctx) { | |
183 | return; | |
184 | } | |
185 | ||
186 | /* | |
187 | * Init one GMainContext for the iothread unconditionally, even if | |
188 | * it's not used | |
189 | */ | |
190 | iothread_init_gcontext(iothread); | |
191 | ||
192 | iothread_set_aio_context_params(iothread, &local_error); | |
193 | if (local_error) { | |
194 | error_propagate(errp, local_error); | |
195 | aio_context_unref(iothread->ctx); | |
196 | iothread->ctx = NULL; | |
197 | return; | |
198 | } | |
199 | ||
200 | /* This assumes we are called from a thread with useful CPU affinity for us | |
201 | * to inherit. | |
202 | */ | |
203 | thread_name = g_strdup_printf("IO %s", | |
204 | object_get_canonical_path_component(OBJECT(obj))); | |
205 | qemu_thread_create(&iothread->thread, thread_name, iothread_run, | |
206 | iothread, QEMU_THREAD_JOINABLE); | |
207 | g_free(thread_name); | |
208 | ||
209 | /* Wait for initialization to complete */ | |
210 | while (iothread->thread_id == -1) { | |
211 | qemu_sem_wait(&iothread->init_done_sem); | |
212 | } | |
213 | } | |
214 | ||
215 | typedef struct { | |
216 | const char *name; | |
217 | ptrdiff_t offset; /* field's byte offset in IOThread struct */ | |
218 | } IOThreadParamInfo; | |
219 | ||
220 | static IOThreadParamInfo poll_max_ns_info = { | |
221 | "poll-max-ns", offsetof(IOThread, poll_max_ns), | |
222 | }; | |
223 | static IOThreadParamInfo poll_grow_info = { | |
224 | "poll-grow", offsetof(IOThread, poll_grow), | |
225 | }; | |
226 | static IOThreadParamInfo poll_shrink_info = { | |
227 | "poll-shrink", offsetof(IOThread, poll_shrink), | |
228 | }; | |
229 | static IOThreadParamInfo aio_max_batch_info = { | |
230 | "aio-max-batch", offsetof(IOThread, aio_max_batch), | |
231 | }; | |
232 | ||
233 | static void iothread_get_param(Object *obj, Visitor *v, | |
234 | const char *name, IOThreadParamInfo *info, Error **errp) | |
235 | { | |
236 | IOThread *iothread = IOTHREAD(obj); | |
237 | int64_t *field = (void *)iothread + info->offset; | |
238 | ||
239 | visit_type_int64(v, name, field, errp); | |
240 | } | |
241 | ||
242 | static bool iothread_set_param(Object *obj, Visitor *v, | |
243 | const char *name, IOThreadParamInfo *info, Error **errp) | |
244 | { | |
245 | IOThread *iothread = IOTHREAD(obj); | |
246 | int64_t *field = (void *)iothread + info->offset; | |
247 | int64_t value; | |
248 | ||
249 | if (!visit_type_int64(v, name, &value, errp)) { | |
250 | return false; | |
251 | } | |
252 | ||
253 | if (value < 0) { | |
254 | error_setg(errp, "%s value must be in range [0, %" PRId64 "]", | |
255 | info->name, INT64_MAX); | |
256 | return false; | |
257 | } | |
258 | ||
259 | *field = value; | |
260 | ||
261 | return true; | |
262 | } | |
263 | ||
264 | static void iothread_get_poll_param(Object *obj, Visitor *v, | |
265 | const char *name, void *opaque, Error **errp) | |
266 | { | |
267 | IOThreadParamInfo *info = opaque; | |
268 | ||
269 | iothread_get_param(obj, v, name, info, errp); | |
270 | } | |
271 | ||
272 | static void iothread_set_poll_param(Object *obj, Visitor *v, | |
273 | const char *name, void *opaque, Error **errp) | |
274 | { | |
275 | IOThread *iothread = IOTHREAD(obj); | |
276 | IOThreadParamInfo *info = opaque; | |
277 | ||
278 | if (!iothread_set_param(obj, v, name, info, errp)) { | |
279 | return; | |
280 | } | |
281 | ||
282 | if (iothread->ctx) { | |
283 | aio_context_set_poll_params(iothread->ctx, | |
284 | iothread->poll_max_ns, | |
285 | iothread->poll_grow, | |
286 | iothread->poll_shrink, | |
287 | errp); | |
288 | } | |
289 | } | |
290 | ||
291 | static void iothread_get_aio_param(Object *obj, Visitor *v, | |
292 | const char *name, void *opaque, Error **errp) | |
293 | { | |
294 | IOThreadParamInfo *info = opaque; | |
295 | ||
296 | iothread_get_param(obj, v, name, info, errp); | |
297 | } | |
298 | ||
299 | static void iothread_set_aio_param(Object *obj, Visitor *v, | |
300 | const char *name, void *opaque, Error **errp) | |
301 | { | |
302 | IOThread *iothread = IOTHREAD(obj); | |
303 | IOThreadParamInfo *info = opaque; | |
304 | ||
305 | if (!iothread_set_param(obj, v, name, info, errp)) { | |
306 | return; | |
307 | } | |
308 | ||
309 | if (iothread->ctx) { | |
310 | aio_context_set_aio_params(iothread->ctx, | |
311 | iothread->aio_max_batch, | |
312 | errp); | |
313 | } | |
314 | } | |
315 | ||
316 | static void iothread_class_init(ObjectClass *klass, void *class_data) | |
317 | { | |
318 | UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); | |
319 | ucc->complete = iothread_complete; | |
320 | ||
321 | object_class_property_add(klass, "poll-max-ns", "int", | |
322 | iothread_get_poll_param, | |
323 | iothread_set_poll_param, | |
324 | NULL, &poll_max_ns_info); | |
325 | object_class_property_add(klass, "poll-grow", "int", | |
326 | iothread_get_poll_param, | |
327 | iothread_set_poll_param, | |
328 | NULL, &poll_grow_info); | |
329 | object_class_property_add(klass, "poll-shrink", "int", | |
330 | iothread_get_poll_param, | |
331 | iothread_set_poll_param, | |
332 | NULL, &poll_shrink_info); | |
333 | object_class_property_add(klass, "aio-max-batch", "int", | |
334 | iothread_get_aio_param, | |
335 | iothread_set_aio_param, | |
336 | NULL, &aio_max_batch_info); | |
337 | } | |
338 | ||
339 | static const TypeInfo iothread_info = { | |
340 | .name = TYPE_IOTHREAD, | |
341 | .parent = TYPE_OBJECT, | |
342 | .class_init = iothread_class_init, | |
343 | .instance_size = sizeof(IOThread), | |
344 | .instance_init = iothread_instance_init, | |
345 | .instance_finalize = iothread_instance_finalize, | |
346 | .interfaces = (InterfaceInfo[]) { | |
347 | {TYPE_USER_CREATABLE}, | |
348 | {} | |
349 | }, | |
350 | }; | |
351 | ||
352 | static void iothread_register_types(void) | |
353 | { | |
354 | type_register_static(&iothread_info); | |
355 | } | |
356 | ||
357 | type_init(iothread_register_types) | |
358 | ||
359 | char *iothread_get_id(IOThread *iothread) | |
360 | { | |
361 | return g_strdup(object_get_canonical_path_component(OBJECT(iothread))); | |
362 | } | |
363 | ||
364 | AioContext *iothread_get_aio_context(IOThread *iothread) | |
365 | { | |
366 | return iothread->ctx; | |
367 | } | |
368 | ||
369 | static int query_one_iothread(Object *object, void *opaque) | |
370 | { | |
371 | IOThreadInfoList ***tail = opaque; | |
372 | IOThreadInfo *info; | |
373 | IOThread *iothread; | |
374 | ||
375 | iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); | |
376 | if (!iothread) { | |
377 | return 0; | |
378 | } | |
379 | ||
380 | info = g_new0(IOThreadInfo, 1); | |
381 | info->id = iothread_get_id(iothread); | |
382 | info->thread_id = iothread->thread_id; | |
383 | info->poll_max_ns = iothread->poll_max_ns; | |
384 | info->poll_grow = iothread->poll_grow; | |
385 | info->poll_shrink = iothread->poll_shrink; | |
386 | info->aio_max_batch = iothread->aio_max_batch; | |
387 | ||
388 | QAPI_LIST_APPEND(*tail, info); | |
389 | return 0; | |
390 | } | |
391 | ||
392 | IOThreadInfoList *qmp_query_iothreads(Error **errp) | |
393 | { | |
394 | IOThreadInfoList *head = NULL; | |
395 | IOThreadInfoList **prev = &head; | |
396 | Object *container = object_get_objects_root(); | |
397 | ||
398 | object_child_foreach(container, query_one_iothread, &prev); | |
399 | return head; | |
400 | } | |
401 | ||
402 | GMainContext *iothread_get_g_main_context(IOThread *iothread) | |
403 | { | |
404 | qatomic_set(&iothread->run_gcontext, 1); | |
405 | aio_notify(iothread->ctx); | |
406 | return iothread->worker_context; | |
407 | } | |
408 | ||
409 | IOThread *iothread_create(const char *id, Error **errp) | |
410 | { | |
411 | Object *obj; | |
412 | ||
413 | obj = object_new_with_props(TYPE_IOTHREAD, | |
414 | object_get_internal_root(), | |
415 | id, errp, NULL); | |
416 | ||
417 | return IOTHREAD(obj); | |
418 | } | |
419 | ||
420 | void iothread_destroy(IOThread *iothread) | |
421 | { | |
422 | object_unparent(OBJECT(iothread)); | |
423 | } | |
424 | ||
425 | /* Lookup IOThread by its id. Only finds user-created objects, not internal | |
426 | * iothread_create() objects. */ | |
427 | IOThread *iothread_by_id(const char *id) | |
428 | { | |
429 | return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); | |
430 | } | |
431 | ||
432 | bool qemu_in_iothread(void) | |
433 | { | |
434 | return qemu_get_current_aio_context() == qemu_get_aio_context() ? | |
435 | false : true; | |
436 | } |