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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/event-loop-base.h" | |
21 | #include "sysemu/iothread.h" | |
22 | #include "qapi/error.h" | |
23 | #include "qapi/qapi-commands-misc.h" | |
24 | #include "qemu/error-report.h" | |
25 | #include "qemu/rcu.h" | |
26 | #include "qemu/main-loop.h" | |
27 | ||
28 | ||
29 | #ifdef CONFIG_POSIX | |
30 | /* Benchmark results from 2016 on NVMe SSD drives show max polling times around | |
31 | * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32 | |
32 | * workloads. | |
33 | */ | |
34 | #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL | |
35 | #else | |
36 | #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL | |
37 | #endif | |
38 | ||
39 | static void *iothread_run(void *opaque) | |
40 | { | |
41 | IOThread *iothread = opaque; | |
42 | ||
43 | rcu_register_thread(); | |
44 | /* | |
45 | * g_main_context_push_thread_default() must be called before anything | |
46 | * in this new thread uses glib. | |
47 | */ | |
48 | g_main_context_push_thread_default(iothread->worker_context); | |
49 | qemu_set_current_aio_context(iothread->ctx); | |
50 | iothread->thread_id = qemu_get_thread_id(); | |
51 | qemu_sem_post(&iothread->init_done_sem); | |
52 | ||
53 | while (iothread->running) { | |
54 | /* | |
55 | * Note: from functional-wise the g_main_loop_run() below can | |
56 | * already cover the aio_poll() events, but we can't run the | |
57 | * main loop unconditionally because explicit aio_poll() here | |
58 | * is faster than g_main_loop_run() when we do not need the | |
59 | * gcontext at all (e.g., pure block layer iothreads). In | |
60 | * other words, when we want to run the gcontext with the | |
61 | * iothread we need to pay some performance for functionality. | |
62 | */ | |
63 | aio_poll(iothread->ctx, true); | |
64 | ||
65 | /* | |
66 | * We must check the running state again in case it was | |
67 | * changed in previous aio_poll() | |
68 | */ | |
69 | if (iothread->running && qatomic_read(&iothread->run_gcontext)) { | |
70 | g_main_loop_run(iothread->main_loop); | |
71 | } | |
72 | } | |
73 | ||
74 | g_main_context_pop_thread_default(iothread->worker_context); | |
75 | rcu_unregister_thread(); | |
76 | return NULL; | |
77 | } | |
78 | ||
79 | /* Runs in iothread_run() thread */ | |
80 | static void iothread_stop_bh(void *opaque) | |
81 | { | |
82 | IOThread *iothread = opaque; | |
83 | ||
84 | iothread->running = false; /* stop iothread_run() */ | |
85 | ||
86 | if (iothread->main_loop) { | |
87 | g_main_loop_quit(iothread->main_loop); | |
88 | } | |
89 | } | |
90 | ||
91 | void iothread_stop(IOThread *iothread) | |
92 | { | |
93 | if (!iothread->ctx || iothread->stopping) { | |
94 | return; | |
95 | } | |
96 | iothread->stopping = true; | |
97 | aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); | |
98 | qemu_thread_join(&iothread->thread); | |
99 | } | |
100 | ||
101 | static void iothread_instance_init(Object *obj) | |
102 | { | |
103 | IOThread *iothread = IOTHREAD(obj); | |
104 | ||
105 | iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT; | |
106 | iothread->thread_id = -1; | |
107 | qemu_sem_init(&iothread->init_done_sem, 0); | |
108 | /* By default, we don't run gcontext */ | |
109 | qatomic_set(&iothread->run_gcontext, 0); | |
110 | } | |
111 | ||
112 | static void iothread_instance_finalize(Object *obj) | |
113 | { | |
114 | IOThread *iothread = IOTHREAD(obj); | |
115 | ||
116 | iothread_stop(iothread); | |
117 | ||
118 | /* | |
119 | * Before glib2 2.33.10, there is a glib2 bug that GSource context | |
120 | * pointer may not be cleared even if the context has already been | |
121 | * destroyed (while it should). Here let's free the AIO context | |
122 | * earlier to bypass that glib bug. | |
123 | * | |
124 | * We can remove this comment after the minimum supported glib2 | |
125 | * version boosts to 2.33.10. Before that, let's free the | |
126 | * GSources first before destroying any GMainContext. | |
127 | */ | |
128 | if (iothread->ctx) { | |
129 | aio_context_unref(iothread->ctx); | |
130 | iothread->ctx = NULL; | |
131 | } | |
132 | if (iothread->worker_context) { | |
133 | g_main_context_unref(iothread->worker_context); | |
134 | iothread->worker_context = NULL; | |
135 | g_main_loop_unref(iothread->main_loop); | |
136 | iothread->main_loop = NULL; | |
137 | } | |
138 | qemu_sem_destroy(&iothread->init_done_sem); | |
139 | } | |
140 | ||
141 | static void iothread_init_gcontext(IOThread *iothread) | |
142 | { | |
143 | GSource *source; | |
144 | ||
145 | iothread->worker_context = g_main_context_new(); | |
146 | source = aio_get_g_source(iothread_get_aio_context(iothread)); | |
147 | g_source_attach(source, iothread->worker_context); | |
148 | g_source_unref(source); | |
149 | iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE); | |
150 | } | |
151 | ||
152 | static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp) | |
153 | { | |
154 | ERRP_GUARD(); | |
155 | IOThread *iothread = IOTHREAD(base); | |
156 | ||
157 | if (!iothread->ctx) { | |
158 | return; | |
159 | } | |
160 | ||
161 | aio_context_set_poll_params(iothread->ctx, | |
162 | iothread->poll_max_ns, | |
163 | iothread->poll_grow, | |
164 | iothread->poll_shrink, | |
165 | errp); | |
166 | if (*errp) { | |
167 | return; | |
168 | } | |
169 | ||
170 | aio_context_set_aio_params(iothread->ctx, | |
171 | iothread->parent_obj.aio_max_batch, | |
172 | errp); | |
173 | ||
174 | aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min, | |
175 | base->thread_pool_max, errp); | |
176 | } | |
177 | ||
178 | ||
179 | static void iothread_init(EventLoopBase *base, Error **errp) | |
180 | { | |
181 | Error *local_error = NULL; | |
182 | IOThread *iothread = IOTHREAD(base); | |
183 | char *thread_name; | |
184 | ||
185 | iothread->stopping = false; | |
186 | iothread->running = true; | |
187 | iothread->ctx = aio_context_new(errp); | |
188 | if (!iothread->ctx) { | |
189 | return; | |
190 | } | |
191 | ||
192 | /* | |
193 | * Init one GMainContext for the iothread unconditionally, even if | |
194 | * it's not used | |
195 | */ | |
196 | iothread_init_gcontext(iothread); | |
197 | ||
198 | iothread_set_aio_context_params(base, &local_error); | |
199 | if (local_error) { | |
200 | error_propagate(errp, local_error); | |
201 | aio_context_unref(iothread->ctx); | |
202 | iothread->ctx = NULL; | |
203 | return; | |
204 | } | |
205 | ||
206 | /* This assumes we are called from a thread with useful CPU affinity for us | |
207 | * to inherit. | |
208 | */ | |
209 | thread_name = g_strdup_printf("IO %s", | |
210 | object_get_canonical_path_component(OBJECT(base))); | |
211 | qemu_thread_create(&iothread->thread, thread_name, iothread_run, | |
212 | iothread, QEMU_THREAD_JOINABLE); | |
213 | g_free(thread_name); | |
214 | ||
215 | /* Wait for initialization to complete */ | |
216 | while (iothread->thread_id == -1) { | |
217 | qemu_sem_wait(&iothread->init_done_sem); | |
218 | } | |
219 | } | |
220 | ||
221 | typedef struct { | |
222 | const char *name; | |
223 | ptrdiff_t offset; /* field's byte offset in IOThread struct */ | |
224 | } IOThreadParamInfo; | |
225 | ||
226 | static IOThreadParamInfo poll_max_ns_info = { | |
227 | "poll-max-ns", offsetof(IOThread, poll_max_ns), | |
228 | }; | |
229 | static IOThreadParamInfo poll_grow_info = { | |
230 | "poll-grow", offsetof(IOThread, poll_grow), | |
231 | }; | |
232 | static IOThreadParamInfo poll_shrink_info = { | |
233 | "poll-shrink", offsetof(IOThread, poll_shrink), | |
234 | }; | |
235 | ||
236 | static void iothread_get_param(Object *obj, Visitor *v, | |
237 | const char *name, IOThreadParamInfo *info, Error **errp) | |
238 | { | |
239 | IOThread *iothread = IOTHREAD(obj); | |
240 | int64_t *field = (void *)iothread + info->offset; | |
241 | ||
242 | visit_type_int64(v, name, field, errp); | |
243 | } | |
244 | ||
245 | static bool iothread_set_param(Object *obj, Visitor *v, | |
246 | const char *name, IOThreadParamInfo *info, Error **errp) | |
247 | { | |
248 | IOThread *iothread = IOTHREAD(obj); | |
249 | int64_t *field = (void *)iothread + info->offset; | |
250 | int64_t value; | |
251 | ||
252 | if (!visit_type_int64(v, name, &value, errp)) { | |
253 | return false; | |
254 | } | |
255 | ||
256 | if (value < 0) { | |
257 | error_setg(errp, "%s value must be in range [0, %" PRId64 "]", | |
258 | info->name, INT64_MAX); | |
259 | return false; | |
260 | } | |
261 | ||
262 | *field = value; | |
263 | ||
264 | return true; | |
265 | } | |
266 | ||
267 | static void iothread_get_poll_param(Object *obj, Visitor *v, | |
268 | const char *name, void *opaque, Error **errp) | |
269 | { | |
270 | IOThreadParamInfo *info = opaque; | |
271 | ||
272 | iothread_get_param(obj, v, name, info, errp); | |
273 | } | |
274 | ||
275 | static void iothread_set_poll_param(Object *obj, Visitor *v, | |
276 | const char *name, void *opaque, Error **errp) | |
277 | { | |
278 | IOThread *iothread = IOTHREAD(obj); | |
279 | IOThreadParamInfo *info = opaque; | |
280 | ||
281 | if (!iothread_set_param(obj, v, name, info, errp)) { | |
282 | return; | |
283 | } | |
284 | ||
285 | if (iothread->ctx) { | |
286 | aio_context_set_poll_params(iothread->ctx, | |
287 | iothread->poll_max_ns, | |
288 | iothread->poll_grow, | |
289 | iothread->poll_shrink, | |
290 | errp); | |
291 | } | |
292 | } | |
293 | ||
294 | static void iothread_class_init(ObjectClass *klass, void *class_data) | |
295 | { | |
296 | EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass); | |
297 | ||
298 | bc->init = iothread_init; | |
299 | bc->update_params = iothread_set_aio_context_params; | |
300 | ||
301 | object_class_property_add(klass, "poll-max-ns", "int", | |
302 | iothread_get_poll_param, | |
303 | iothread_set_poll_param, | |
304 | NULL, &poll_max_ns_info); | |
305 | object_class_property_add(klass, "poll-grow", "int", | |
306 | iothread_get_poll_param, | |
307 | iothread_set_poll_param, | |
308 | NULL, &poll_grow_info); | |
309 | object_class_property_add(klass, "poll-shrink", "int", | |
310 | iothread_get_poll_param, | |
311 | iothread_set_poll_param, | |
312 | NULL, &poll_shrink_info); | |
313 | } | |
314 | ||
315 | static const TypeInfo iothread_info = { | |
316 | .name = TYPE_IOTHREAD, | |
317 | .parent = TYPE_EVENT_LOOP_BASE, | |
318 | .class_init = iothread_class_init, | |
319 | .instance_size = sizeof(IOThread), | |
320 | .instance_init = iothread_instance_init, | |
321 | .instance_finalize = iothread_instance_finalize, | |
322 | }; | |
323 | ||
324 | static void iothread_register_types(void) | |
325 | { | |
326 | type_register_static(&iothread_info); | |
327 | } | |
328 | ||
329 | type_init(iothread_register_types) | |
330 | ||
331 | char *iothread_get_id(IOThread *iothread) | |
332 | { | |
333 | return g_strdup(object_get_canonical_path_component(OBJECT(iothread))); | |
334 | } | |
335 | ||
336 | AioContext *iothread_get_aio_context(IOThread *iothread) | |
337 | { | |
338 | return iothread->ctx; | |
339 | } | |
340 | ||
341 | static int query_one_iothread(Object *object, void *opaque) | |
342 | { | |
343 | IOThreadInfoList ***tail = opaque; | |
344 | IOThreadInfo *info; | |
345 | IOThread *iothread; | |
346 | ||
347 | iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); | |
348 | if (!iothread) { | |
349 | return 0; | |
350 | } | |
351 | ||
352 | info = g_new0(IOThreadInfo, 1); | |
353 | info->id = iothread_get_id(iothread); | |
354 | info->thread_id = iothread->thread_id; | |
355 | info->poll_max_ns = iothread->poll_max_ns; | |
356 | info->poll_grow = iothread->poll_grow; | |
357 | info->poll_shrink = iothread->poll_shrink; | |
358 | info->aio_max_batch = iothread->parent_obj.aio_max_batch; | |
359 | ||
360 | QAPI_LIST_APPEND(*tail, info); | |
361 | return 0; | |
362 | } | |
363 | ||
364 | IOThreadInfoList *qmp_query_iothreads(Error **errp) | |
365 | { | |
366 | IOThreadInfoList *head = NULL; | |
367 | IOThreadInfoList **prev = &head; | |
368 | Object *container = object_get_objects_root(); | |
369 | ||
370 | object_child_foreach(container, query_one_iothread, &prev); | |
371 | return head; | |
372 | } | |
373 | ||
374 | GMainContext *iothread_get_g_main_context(IOThread *iothread) | |
375 | { | |
376 | qatomic_set(&iothread->run_gcontext, 1); | |
377 | aio_notify(iothread->ctx); | |
378 | return iothread->worker_context; | |
379 | } | |
380 | ||
381 | IOThread *iothread_create(const char *id, Error **errp) | |
382 | { | |
383 | Object *obj; | |
384 | ||
385 | obj = object_new_with_props(TYPE_IOTHREAD, | |
386 | object_get_internal_root(), | |
387 | id, errp, NULL); | |
388 | ||
389 | return IOTHREAD(obj); | |
390 | } | |
391 | ||
392 | void iothread_destroy(IOThread *iothread) | |
393 | { | |
394 | object_unparent(OBJECT(iothread)); | |
395 | } | |
396 | ||
397 | /* Lookup IOThread by its id. Only finds user-created objects, not internal | |
398 | * iothread_create() objects. */ | |
399 | IOThread *iothread_by_id(const char *id) | |
400 | { | |
401 | return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); | |
402 | } | |
403 | ||
404 | bool qemu_in_iothread(void) | |
405 | { | |
406 | return qemu_get_current_aio_context() == qemu_get_aio_context() ? | |
407 | false : true; | |
408 | } |