Merge tag 'pull-aspeed-20220525' of https://github.com/legoater/qemu into staging
[qemu.git] / iothread.c
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 typedef ObjectClass IOThreadClass;
29
30 DECLARE_CLASS_CHECKERS(IOThreadClass, IOTHREAD,
31 TYPE_IOTHREAD)
32
33 #ifdef CONFIG_POSIX
34 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around
35 * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32
36 * workloads.
37 */
38 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL
39 #else
40 #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL
41 #endif
42
43 static void *iothread_run(void *opaque)
44 {
45 IOThread *iothread = opaque;
46
47 rcu_register_thread();
48 /*
49 * g_main_context_push_thread_default() must be called before anything
50 * in this new thread uses glib.
51 */
52 g_main_context_push_thread_default(iothread->worker_context);
53 qemu_set_current_aio_context(iothread->ctx);
54 iothread->thread_id = qemu_get_thread_id();
55 qemu_sem_post(&iothread->init_done_sem);
56
57 while (iothread->running) {
58 /*
59 * Note: from functional-wise the g_main_loop_run() below can
60 * already cover the aio_poll() events, but we can't run the
61 * main loop unconditionally because explicit aio_poll() here
62 * is faster than g_main_loop_run() when we do not need the
63 * gcontext at all (e.g., pure block layer iothreads). In
64 * other words, when we want to run the gcontext with the
65 * iothread we need to pay some performance for functionality.
66 */
67 aio_poll(iothread->ctx, true);
68
69 /*
70 * We must check the running state again in case it was
71 * changed in previous aio_poll()
72 */
73 if (iothread->running && qatomic_read(&iothread->run_gcontext)) {
74 g_main_loop_run(iothread->main_loop);
75 }
76 }
77
78 g_main_context_pop_thread_default(iothread->worker_context);
79 rcu_unregister_thread();
80 return NULL;
81 }
82
83 /* Runs in iothread_run() thread */
84 static void iothread_stop_bh(void *opaque)
85 {
86 IOThread *iothread = opaque;
87
88 iothread->running = false; /* stop iothread_run() */
89
90 if (iothread->main_loop) {
91 g_main_loop_quit(iothread->main_loop);
92 }
93 }
94
95 void iothread_stop(IOThread *iothread)
96 {
97 if (!iothread->ctx || iothread->stopping) {
98 return;
99 }
100 iothread->stopping = true;
101 aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
102 qemu_thread_join(&iothread->thread);
103 }
104
105 static void iothread_instance_init(Object *obj)
106 {
107 IOThread *iothread = IOTHREAD(obj);
108
109 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
110 iothread->thread_id = -1;
111 qemu_sem_init(&iothread->init_done_sem, 0);
112 /* By default, we don't run gcontext */
113 qatomic_set(&iothread->run_gcontext, 0);
114 }
115
116 static void iothread_instance_finalize(Object *obj)
117 {
118 IOThread *iothread = IOTHREAD(obj);
119
120 iothread_stop(iothread);
121
122 /*
123 * Before glib2 2.33.10, there is a glib2 bug that GSource context
124 * pointer may not be cleared even if the context has already been
125 * destroyed (while it should). Here let's free the AIO context
126 * earlier to bypass that glib bug.
127 *
128 * We can remove this comment after the minimum supported glib2
129 * version boosts to 2.33.10. Before that, let's free the
130 * GSources first before destroying any GMainContext.
131 */
132 if (iothread->ctx) {
133 aio_context_unref(iothread->ctx);
134 iothread->ctx = NULL;
135 }
136 if (iothread->worker_context) {
137 g_main_context_unref(iothread->worker_context);
138 iothread->worker_context = NULL;
139 g_main_loop_unref(iothread->main_loop);
140 iothread->main_loop = NULL;
141 }
142 qemu_sem_destroy(&iothread->init_done_sem);
143 }
144
145 static void iothread_init_gcontext(IOThread *iothread)
146 {
147 GSource *source;
148
149 iothread->worker_context = g_main_context_new();
150 source = aio_get_g_source(iothread_get_aio_context(iothread));
151 g_source_attach(source, iothread->worker_context);
152 g_source_unref(source);
153 iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);
154 }
155
156 static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp)
157 {
158 IOThread *iothread = IOTHREAD(base);
159 ERRP_GUARD();
160
161 if (!iothread->ctx) {
162 return;
163 }
164
165 aio_context_set_poll_params(iothread->ctx,
166 iothread->poll_max_ns,
167 iothread->poll_grow,
168 iothread->poll_shrink,
169 errp);
170 if (*errp) {
171 return;
172 }
173
174 aio_context_set_aio_params(iothread->ctx,
175 iothread->parent_obj.aio_max_batch,
176 errp);
177
178 aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min,
179 base->thread_pool_max, errp);
180 }
181
182
183 static void iothread_init(EventLoopBase *base, Error **errp)
184 {
185 Error *local_error = NULL;
186 IOThread *iothread = IOTHREAD(base);
187 char *thread_name;
188
189 iothread->stopping = false;
190 iothread->running = true;
191 iothread->ctx = aio_context_new(errp);
192 if (!iothread->ctx) {
193 return;
194 }
195
196 /*
197 * Init one GMainContext for the iothread unconditionally, even if
198 * it's not used
199 */
200 iothread_init_gcontext(iothread);
201
202 iothread_set_aio_context_params(base, &local_error);
203 if (local_error) {
204 error_propagate(errp, local_error);
205 aio_context_unref(iothread->ctx);
206 iothread->ctx = NULL;
207 return;
208 }
209
210 /* This assumes we are called from a thread with useful CPU affinity for us
211 * to inherit.
212 */
213 thread_name = g_strdup_printf("IO %s",
214 object_get_canonical_path_component(OBJECT(base)));
215 qemu_thread_create(&iothread->thread, thread_name, iothread_run,
216 iothread, QEMU_THREAD_JOINABLE);
217 g_free(thread_name);
218
219 /* Wait for initialization to complete */
220 while (iothread->thread_id == -1) {
221 qemu_sem_wait(&iothread->init_done_sem);
222 }
223 }
224
225 typedef struct {
226 const char *name;
227 ptrdiff_t offset; /* field's byte offset in IOThread struct */
228 } IOThreadParamInfo;
229
230 static IOThreadParamInfo poll_max_ns_info = {
231 "poll-max-ns", offsetof(IOThread, poll_max_ns),
232 };
233 static IOThreadParamInfo poll_grow_info = {
234 "poll-grow", offsetof(IOThread, poll_grow),
235 };
236 static IOThreadParamInfo poll_shrink_info = {
237 "poll-shrink", offsetof(IOThread, poll_shrink),
238 };
239
240 static void iothread_get_param(Object *obj, Visitor *v,
241 const char *name, IOThreadParamInfo *info, Error **errp)
242 {
243 IOThread *iothread = IOTHREAD(obj);
244 int64_t *field = (void *)iothread + info->offset;
245
246 visit_type_int64(v, name, field, errp);
247 }
248
249 static bool iothread_set_param(Object *obj, Visitor *v,
250 const char *name, IOThreadParamInfo *info, Error **errp)
251 {
252 IOThread *iothread = IOTHREAD(obj);
253 int64_t *field = (void *)iothread + info->offset;
254 int64_t value;
255
256 if (!visit_type_int64(v, name, &value, errp)) {
257 return false;
258 }
259
260 if (value < 0) {
261 error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
262 info->name, INT64_MAX);
263 return false;
264 }
265
266 *field = value;
267
268 return true;
269 }
270
271 static void iothread_get_poll_param(Object *obj, Visitor *v,
272 const char *name, void *opaque, Error **errp)
273 {
274 IOThreadParamInfo *info = opaque;
275
276 iothread_get_param(obj, v, name, info, errp);
277 }
278
279 static void iothread_set_poll_param(Object *obj, Visitor *v,
280 const char *name, void *opaque, Error **errp)
281 {
282 IOThread *iothread = IOTHREAD(obj);
283 IOThreadParamInfo *info = opaque;
284
285 if (!iothread_set_param(obj, v, name, info, errp)) {
286 return;
287 }
288
289 if (iothread->ctx) {
290 aio_context_set_poll_params(iothread->ctx,
291 iothread->poll_max_ns,
292 iothread->poll_grow,
293 iothread->poll_shrink,
294 errp);
295 }
296 }
297
298 static void iothread_class_init(ObjectClass *klass, void *class_data)
299 {
300 EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass);
301
302 bc->init = iothread_init;
303 bc->update_params = iothread_set_aio_context_params;
304
305 object_class_property_add(klass, "poll-max-ns", "int",
306 iothread_get_poll_param,
307 iothread_set_poll_param,
308 NULL, &poll_max_ns_info);
309 object_class_property_add(klass, "poll-grow", "int",
310 iothread_get_poll_param,
311 iothread_set_poll_param,
312 NULL, &poll_grow_info);
313 object_class_property_add(klass, "poll-shrink", "int",
314 iothread_get_poll_param,
315 iothread_set_poll_param,
316 NULL, &poll_shrink_info);
317 }
318
319 static const TypeInfo iothread_info = {
320 .name = TYPE_IOTHREAD,
321 .parent = TYPE_EVENT_LOOP_BASE,
322 .class_init = iothread_class_init,
323 .instance_size = sizeof(IOThread),
324 .instance_init = iothread_instance_init,
325 .instance_finalize = iothread_instance_finalize,
326 };
327
328 static void iothread_register_types(void)
329 {
330 type_register_static(&iothread_info);
331 }
332
333 type_init(iothread_register_types)
334
335 char *iothread_get_id(IOThread *iothread)
336 {
337 return g_strdup(object_get_canonical_path_component(OBJECT(iothread)));
338 }
339
340 AioContext *iothread_get_aio_context(IOThread *iothread)
341 {
342 return iothread->ctx;
343 }
344
345 static int query_one_iothread(Object *object, void *opaque)
346 {
347 IOThreadInfoList ***tail = opaque;
348 IOThreadInfo *info;
349 IOThread *iothread;
350
351 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
352 if (!iothread) {
353 return 0;
354 }
355
356 info = g_new0(IOThreadInfo, 1);
357 info->id = iothread_get_id(iothread);
358 info->thread_id = iothread->thread_id;
359 info->poll_max_ns = iothread->poll_max_ns;
360 info->poll_grow = iothread->poll_grow;
361 info->poll_shrink = iothread->poll_shrink;
362 info->aio_max_batch = iothread->parent_obj.aio_max_batch;
363
364 QAPI_LIST_APPEND(*tail, info);
365 return 0;
366 }
367
368 IOThreadInfoList *qmp_query_iothreads(Error **errp)
369 {
370 IOThreadInfoList *head = NULL;
371 IOThreadInfoList **prev = &head;
372 Object *container = object_get_objects_root();
373
374 object_child_foreach(container, query_one_iothread, &prev);
375 return head;
376 }
377
378 GMainContext *iothread_get_g_main_context(IOThread *iothread)
379 {
380 qatomic_set(&iothread->run_gcontext, 1);
381 aio_notify(iothread->ctx);
382 return iothread->worker_context;
383 }
384
385 IOThread *iothread_create(const char *id, Error **errp)
386 {
387 Object *obj;
388
389 obj = object_new_with_props(TYPE_IOTHREAD,
390 object_get_internal_root(),
391 id, errp, NULL);
392
393 return IOTHREAD(obj);
394 }
395
396 void iothread_destroy(IOThread *iothread)
397 {
398 object_unparent(OBJECT(iothread));
399 }
400
401 /* Lookup IOThread by its id. Only finds user-created objects, not internal
402 * iothread_create() objects. */
403 IOThread *iothread_by_id(const char *id)
404 {
405 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
406 }
407
408 bool qemu_in_iothread(void)
409 {
410 return qemu_get_current_aio_context() == qemu_get_aio_context() ?
411 false : true;
412 }