Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2017-03-16' into staging
[qemu.git] / iothread.c
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 "qmp-commands.h"
22 #include "qemu/error-report.h"
23 #include "qemu/rcu.h"
24 #include "qemu/main-loop.h"
25
26 typedef ObjectClass IOThreadClass;
27
28 #define IOTHREAD_GET_CLASS(obj) \
29 OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
30 #define IOTHREAD_CLASS(klass) \
31 OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
32
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
39 static __thread IOThread *my_iothread;
40
41 AioContext *qemu_get_current_aio_context(void)
42 {
43 return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
44 }
45
46 static void *iothread_run(void *opaque)
47 {
48 IOThread *iothread = opaque;
49
50 rcu_register_thread();
51
52 my_iothread = iothread;
53 qemu_mutex_lock(&iothread->init_done_lock);
54 iothread->thread_id = qemu_get_thread_id();
55 qemu_cond_signal(&iothread->init_done_cond);
56 qemu_mutex_unlock(&iothread->init_done_lock);
57
58 while (!atomic_read(&iothread->stopping)) {
59 aio_poll(iothread->ctx, true);
60 }
61
62 rcu_unregister_thread();
63 return NULL;
64 }
65
66 static int iothread_stop(Object *object, void *opaque)
67 {
68 IOThread *iothread;
69
70 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
71 if (!iothread || !iothread->ctx) {
72 return 0;
73 }
74 iothread->stopping = true;
75 aio_notify(iothread->ctx);
76 qemu_thread_join(&iothread->thread);
77 return 0;
78 }
79
80 static void iothread_instance_init(Object *obj)
81 {
82 IOThread *iothread = IOTHREAD(obj);
83
84 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
85 }
86
87 static void iothread_instance_finalize(Object *obj)
88 {
89 IOThread *iothread = IOTHREAD(obj);
90
91 iothread_stop(obj, NULL);
92 qemu_cond_destroy(&iothread->init_done_cond);
93 qemu_mutex_destroy(&iothread->init_done_lock);
94 if (!iothread->ctx) {
95 return;
96 }
97 aio_context_unref(iothread->ctx);
98 }
99
100 static void iothread_complete(UserCreatable *obj, Error **errp)
101 {
102 Error *local_error = NULL;
103 IOThread *iothread = IOTHREAD(obj);
104 char *name, *thread_name;
105
106 iothread->stopping = false;
107 iothread->thread_id = -1;
108 iothread->ctx = aio_context_new(&local_error);
109 if (!iothread->ctx) {
110 error_propagate(errp, local_error);
111 return;
112 }
113
114 aio_context_set_poll_params(iothread->ctx,
115 iothread->poll_max_ns,
116 iothread->poll_grow,
117 iothread->poll_shrink,
118 &local_error);
119 if (local_error) {
120 error_propagate(errp, local_error);
121 aio_context_unref(iothread->ctx);
122 iothread->ctx = NULL;
123 return;
124 }
125
126 qemu_mutex_init(&iothread->init_done_lock);
127 qemu_cond_init(&iothread->init_done_cond);
128
129 /* This assumes we are called from a thread with useful CPU affinity for us
130 * to inherit.
131 */
132 name = object_get_canonical_path_component(OBJECT(obj));
133 thread_name = g_strdup_printf("IO %s", name);
134 qemu_thread_create(&iothread->thread, thread_name, iothread_run,
135 iothread, QEMU_THREAD_JOINABLE);
136 g_free(thread_name);
137 g_free(name);
138
139 /* Wait for initialization to complete */
140 qemu_mutex_lock(&iothread->init_done_lock);
141 while (iothread->thread_id == -1) {
142 qemu_cond_wait(&iothread->init_done_cond,
143 &iothread->init_done_lock);
144 }
145 qemu_mutex_unlock(&iothread->init_done_lock);
146 }
147
148 typedef struct {
149 const char *name;
150 ptrdiff_t offset; /* field's byte offset in IOThread struct */
151 } PollParamInfo;
152
153 static PollParamInfo poll_max_ns_info = {
154 "poll-max-ns", offsetof(IOThread, poll_max_ns),
155 };
156 static PollParamInfo poll_grow_info = {
157 "poll-grow", offsetof(IOThread, poll_grow),
158 };
159 static PollParamInfo poll_shrink_info = {
160 "poll-shrink", offsetof(IOThread, poll_shrink),
161 };
162
163 static void iothread_get_poll_param(Object *obj, Visitor *v,
164 const char *name, void *opaque, Error **errp)
165 {
166 IOThread *iothread = IOTHREAD(obj);
167 PollParamInfo *info = opaque;
168 int64_t *field = (void *)iothread + info->offset;
169
170 visit_type_int64(v, name, field, errp);
171 }
172
173 static void iothread_set_poll_param(Object *obj, Visitor *v,
174 const char *name, void *opaque, Error **errp)
175 {
176 IOThread *iothread = IOTHREAD(obj);
177 PollParamInfo *info = opaque;
178 int64_t *field = (void *)iothread + info->offset;
179 Error *local_err = NULL;
180 int64_t value;
181
182 visit_type_int64(v, name, &value, &local_err);
183 if (local_err) {
184 goto out;
185 }
186
187 if (value < 0) {
188 error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
189 info->name, INT64_MAX);
190 goto out;
191 }
192
193 *field = value;
194
195 if (iothread->ctx) {
196 aio_context_set_poll_params(iothread->ctx,
197 iothread->poll_max_ns,
198 iothread->poll_grow,
199 iothread->poll_shrink,
200 &local_err);
201 }
202
203 out:
204 error_propagate(errp, local_err);
205 }
206
207 static void iothread_class_init(ObjectClass *klass, void *class_data)
208 {
209 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
210 ucc->complete = iothread_complete;
211
212 object_class_property_add(klass, "poll-max-ns", "int",
213 iothread_get_poll_param,
214 iothread_set_poll_param,
215 NULL, &poll_max_ns_info, &error_abort);
216 object_class_property_add(klass, "poll-grow", "int",
217 iothread_get_poll_param,
218 iothread_set_poll_param,
219 NULL, &poll_grow_info, &error_abort);
220 object_class_property_add(klass, "poll-shrink", "int",
221 iothread_get_poll_param,
222 iothread_set_poll_param,
223 NULL, &poll_shrink_info, &error_abort);
224 }
225
226 static const TypeInfo iothread_info = {
227 .name = TYPE_IOTHREAD,
228 .parent = TYPE_OBJECT,
229 .class_init = iothread_class_init,
230 .instance_size = sizeof(IOThread),
231 .instance_init = iothread_instance_init,
232 .instance_finalize = iothread_instance_finalize,
233 .interfaces = (InterfaceInfo[]) {
234 {TYPE_USER_CREATABLE},
235 {}
236 },
237 };
238
239 static void iothread_register_types(void)
240 {
241 type_register_static(&iothread_info);
242 }
243
244 type_init(iothread_register_types)
245
246 char *iothread_get_id(IOThread *iothread)
247 {
248 return object_get_canonical_path_component(OBJECT(iothread));
249 }
250
251 AioContext *iothread_get_aio_context(IOThread *iothread)
252 {
253 return iothread->ctx;
254 }
255
256 static int query_one_iothread(Object *object, void *opaque)
257 {
258 IOThreadInfoList ***prev = opaque;
259 IOThreadInfoList *elem;
260 IOThreadInfo *info;
261 IOThread *iothread;
262
263 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
264 if (!iothread) {
265 return 0;
266 }
267
268 info = g_new0(IOThreadInfo, 1);
269 info->id = iothread_get_id(iothread);
270 info->thread_id = iothread->thread_id;
271 info->poll_max_ns = iothread->poll_max_ns;
272 info->poll_grow = iothread->poll_grow;
273 info->poll_shrink = iothread->poll_shrink;
274
275 elem = g_new0(IOThreadInfoList, 1);
276 elem->value = info;
277 elem->next = NULL;
278
279 **prev = elem;
280 *prev = &elem->next;
281 return 0;
282 }
283
284 IOThreadInfoList *qmp_query_iothreads(Error **errp)
285 {
286 IOThreadInfoList *head = NULL;
287 IOThreadInfoList **prev = &head;
288 Object *container = object_get_objects_root();
289
290 object_child_foreach(container, query_one_iothread, &prev);
291 return head;
292 }
293
294 void iothread_stop_all(void)
295 {
296 Object *container = object_get_objects_root();
297 BlockDriverState *bs;
298 BdrvNextIterator it;
299
300 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
301 AioContext *ctx = bdrv_get_aio_context(bs);
302 if (ctx == qemu_get_aio_context()) {
303 continue;
304 }
305 aio_context_acquire(ctx);
306 bdrv_set_aio_context(bs, qemu_get_aio_context());
307 aio_context_release(ctx);
308 }
309
310 object_child_foreach(container, iothread_stop, NULL);
311 }