Merge remote-tracking branch 'remotes/vivier2/tags/linux-user-for-6.2-pull-request...
[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/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_complete(UserCreatable *obj, Error **errp)
156 {
157 Error *local_error = NULL;
158 IOThread *iothread = IOTHREAD(obj);
159 char *thread_name;
160
161 iothread->stopping = false;
162 iothread->running = true;
163 iothread->ctx = aio_context_new(errp);
164 if (!iothread->ctx) {
165 return;
166 }
167
168 /*
169 * Init one GMainContext for the iothread unconditionally, even if
170 * it's not used
171 */
172 iothread_init_gcontext(iothread);
173
174 aio_context_set_poll_params(iothread->ctx,
175 iothread->poll_max_ns,
176 iothread->poll_grow,
177 iothread->poll_shrink,
178 &local_error);
179 if (local_error) {
180 error_propagate(errp, local_error);
181 aio_context_unref(iothread->ctx);
182 iothread->ctx = NULL;
183 return;
184 }
185
186 /* This assumes we are called from a thread with useful CPU affinity for us
187 * to inherit.
188 */
189 thread_name = g_strdup_printf("IO %s",
190 object_get_canonical_path_component(OBJECT(obj)));
191 qemu_thread_create(&iothread->thread, thread_name, iothread_run,
192 iothread, QEMU_THREAD_JOINABLE);
193 g_free(thread_name);
194
195 /* Wait for initialization to complete */
196 while (iothread->thread_id == -1) {
197 qemu_sem_wait(&iothread->init_done_sem);
198 }
199 }
200
201 typedef struct {
202 const char *name;
203 ptrdiff_t offset; /* field's byte offset in IOThread struct */
204 } PollParamInfo;
205
206 static PollParamInfo poll_max_ns_info = {
207 "poll-max-ns", offsetof(IOThread, poll_max_ns),
208 };
209 static PollParamInfo poll_grow_info = {
210 "poll-grow", offsetof(IOThread, poll_grow),
211 };
212 static PollParamInfo poll_shrink_info = {
213 "poll-shrink", offsetof(IOThread, poll_shrink),
214 };
215
216 static void iothread_get_poll_param(Object *obj, Visitor *v,
217 const char *name, void *opaque, Error **errp)
218 {
219 IOThread *iothread = IOTHREAD(obj);
220 PollParamInfo *info = opaque;
221 int64_t *field = (void *)iothread + info->offset;
222
223 visit_type_int64(v, name, field, errp);
224 }
225
226 static void iothread_set_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 int64_t value;
233
234 if (!visit_type_int64(v, name, &value, errp)) {
235 return;
236 }
237
238 if (value < 0) {
239 error_setg(errp, "%s value must be in range [0, %" PRId64 "]",
240 info->name, INT64_MAX);
241 return;
242 }
243
244 *field = value;
245
246 if (iothread->ctx) {
247 aio_context_set_poll_params(iothread->ctx,
248 iothread->poll_max_ns,
249 iothread->poll_grow,
250 iothread->poll_shrink,
251 errp);
252 }
253 }
254
255 static void iothread_class_init(ObjectClass *klass, void *class_data)
256 {
257 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
258 ucc->complete = iothread_complete;
259
260 object_class_property_add(klass, "poll-max-ns", "int",
261 iothread_get_poll_param,
262 iothread_set_poll_param,
263 NULL, &poll_max_ns_info);
264 object_class_property_add(klass, "poll-grow", "int",
265 iothread_get_poll_param,
266 iothread_set_poll_param,
267 NULL, &poll_grow_info);
268 object_class_property_add(klass, "poll-shrink", "int",
269 iothread_get_poll_param,
270 iothread_set_poll_param,
271 NULL, &poll_shrink_info);
272 }
273
274 static const TypeInfo iothread_info = {
275 .name = TYPE_IOTHREAD,
276 .parent = TYPE_OBJECT,
277 .class_init = iothread_class_init,
278 .instance_size = sizeof(IOThread),
279 .instance_init = iothread_instance_init,
280 .instance_finalize = iothread_instance_finalize,
281 .interfaces = (InterfaceInfo[]) {
282 {TYPE_USER_CREATABLE},
283 {}
284 },
285 };
286
287 static void iothread_register_types(void)
288 {
289 type_register_static(&iothread_info);
290 }
291
292 type_init(iothread_register_types)
293
294 char *iothread_get_id(IOThread *iothread)
295 {
296 return g_strdup(object_get_canonical_path_component(OBJECT(iothread)));
297 }
298
299 AioContext *iothread_get_aio_context(IOThread *iothread)
300 {
301 return iothread->ctx;
302 }
303
304 static int query_one_iothread(Object *object, void *opaque)
305 {
306 IOThreadInfoList ***tail = opaque;
307 IOThreadInfo *info;
308 IOThread *iothread;
309
310 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
311 if (!iothread) {
312 return 0;
313 }
314
315 info = g_new0(IOThreadInfo, 1);
316 info->id = iothread_get_id(iothread);
317 info->thread_id = iothread->thread_id;
318 info->poll_max_ns = iothread->poll_max_ns;
319 info->poll_grow = iothread->poll_grow;
320 info->poll_shrink = iothread->poll_shrink;
321
322 QAPI_LIST_APPEND(*tail, info);
323 return 0;
324 }
325
326 IOThreadInfoList *qmp_query_iothreads(Error **errp)
327 {
328 IOThreadInfoList *head = NULL;
329 IOThreadInfoList **prev = &head;
330 Object *container = object_get_objects_root();
331
332 object_child_foreach(container, query_one_iothread, &prev);
333 return head;
334 }
335
336 GMainContext *iothread_get_g_main_context(IOThread *iothread)
337 {
338 qatomic_set(&iothread->run_gcontext, 1);
339 aio_notify(iothread->ctx);
340 return iothread->worker_context;
341 }
342
343 IOThread *iothread_create(const char *id, Error **errp)
344 {
345 Object *obj;
346
347 obj = object_new_with_props(TYPE_IOTHREAD,
348 object_get_internal_root(),
349 id, errp, NULL);
350
351 return IOTHREAD(obj);
352 }
353
354 void iothread_destroy(IOThread *iothread)
355 {
356 object_unparent(OBJECT(iothread));
357 }
358
359 /* Lookup IOThread by its id. Only finds user-created objects, not internal
360 * iothread_create() objects. */
361 IOThread *iothread_by_id(const char *id)
362 {
363 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
364 }
365
366 bool qemu_in_iothread(void)
367 {
368 return qemu_get_current_aio_context() == qemu_get_aio_context() ?
369 false : true;
370 }