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 | } |
387 | |