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1 | /* |
2 | * lttng-context-perf-counters.c | |
3 | * | |
4 | * LTTng UST performance monitoring counters (perf-counters) integration. | |
5 | * | |
6 | * Copyright (C) 2009-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * | |
8 | * This library is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License as published by the Free Software Foundation; only | |
11 | * version 2.1 of the License. | |
12 | * | |
13 | * This library is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * Lesser General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Lesser General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
21 | */ | |
22 | ||
23 | #include <sys/types.h> | |
24 | #include <unistd.h> | |
25 | #include <string.h> | |
26 | #include <stdlib.h> | |
27 | #include <stdio.h> | |
28 | #include <sys/mman.h> | |
29 | #include <sys/syscall.h> | |
30 | #include <linux/perf_event.h> | |
31 | #include <lttng/ust-events.h> | |
32 | #include <lttng/ust-tracer.h> | |
33 | #include <lttng/ringbuffer-config.h> | |
34 | #include <urcu/system.h> | |
35 | #include <urcu/arch.h> | |
36 | #include <urcu/rculist.h> | |
37 | #include <helper.h> | |
38 | #include <urcu/ref.h> | |
39 | #include <usterr-signal-safe.h> | |
40 | #include <signal.h> | |
41 | #include "lttng-tracer-core.h" | |
42 | ||
43 | /* | |
44 | * We use a global perf counter key and iterate on per-thread RCU lists | |
45 | * of fields in the fast path, even though this is not strictly speaking | |
46 | * what would provide the best fast-path complexity, to ensure teardown | |
47 | * of sessions vs thread exit is handled racelessly. | |
48 | * | |
49 | * Updates and traversals of thread_list are protected by UST lock. | |
50 | * Updates to rcu_field_list are protected by UST lock. | |
51 | */ | |
52 | ||
53 | struct lttng_perf_counter_thread_field { | |
54 | struct lttng_perf_counter_field *field; /* Back reference */ | |
55 | struct perf_event_mmap_page *pc; | |
56 | struct cds_list_head thread_field_node; /* Per-field list of thread fields (node) */ | |
57 | struct cds_list_head rcu_field_node; /* RCU per-thread list of fields (node) */ | |
58 | }; | |
59 | ||
60 | struct lttng_perf_counter_thread { | |
61 | struct cds_list_head rcu_field_list; /* RCU per-thread list of fields */ | |
62 | }; | |
63 | ||
64 | struct lttng_perf_counter_field { | |
65 | struct perf_event_attr attr; | |
66 | struct cds_list_head thread_field_list; /* Per-field list of thread fields */ | |
67 | }; | |
68 | ||
69 | static pthread_key_t perf_counter_key; | |
70 | ||
71 | static | |
72 | size_t perf_counter_get_size(size_t offset) | |
73 | { | |
74 | size_t size = 0; | |
75 | ||
76 | size += lib_ring_buffer_align(offset, lttng_alignof(uint64_t)); | |
77 | size += sizeof(uint64_t); | |
78 | return size; | |
79 | } | |
80 | ||
81 | #if defined(__x86_64__) || defined(__i386__) | |
82 | ||
83 | static | |
84 | uint64_t rdpmc(unsigned int counter) | |
85 | { | |
86 | unsigned int low, high; | |
87 | ||
88 | asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter)); | |
89 | ||
90 | return low | ((uint64_t) high) << 32; | |
91 | } | |
92 | ||
93 | #else /* defined(__x86_64__) || defined(__i386__) */ | |
94 | ||
95 | #error "Perf event counters are only supported on x86 so far." | |
96 | ||
97 | #endif /* #else defined(__x86_64__) || defined(__i386__) */ | |
98 | ||
99 | static | |
100 | uint64_t read_perf_counter(struct perf_event_mmap_page *pc) | |
101 | { | |
102 | uint32_t seq, idx; | |
103 | uint64_t count; | |
104 | ||
105 | if (caa_unlikely(!pc)) | |
106 | return 0; | |
107 | ||
108 | do { | |
109 | seq = CMM_LOAD_SHARED(pc->lock); | |
110 | cmm_barrier(); | |
111 | ||
112 | idx = pc->index; | |
113 | if (idx) | |
114 | count = pc->offset + rdpmc(idx - 1); | |
115 | else | |
116 | count = 0; | |
117 | ||
118 | cmm_barrier(); | |
119 | } while (CMM_LOAD_SHARED(pc->lock) != seq); | |
120 | ||
121 | return count; | |
122 | } | |
123 | ||
124 | static | |
125 | int sys_perf_event_open(struct perf_event_attr *attr, | |
126 | pid_t pid, int cpu, int group_fd, | |
127 | unsigned long flags) | |
128 | { | |
129 | return syscall(SYS_perf_event_open, attr, pid, cpu, | |
130 | group_fd, flags); | |
131 | } | |
132 | ||
133 | static | |
134 | struct perf_event_mmap_page *setup_perf(struct perf_event_attr *attr) | |
135 | { | |
136 | void *perf_addr; | |
137 | int fd; | |
138 | ||
139 | fd = sys_perf_event_open(attr, 0, -1, -1, 0); | |
140 | if (fd < 0) | |
141 | return NULL; | |
142 | ||
143 | perf_addr = mmap(NULL, sizeof(struct perf_event_mmap_page), | |
144 | PROT_READ, MAP_SHARED, fd, 0); | |
145 | if (perf_addr == MAP_FAILED) | |
146 | return NULL; | |
147 | close(fd); | |
148 | return perf_addr; | |
149 | } | |
150 | ||
151 | static | |
152 | void unmap_perf_page(struct perf_event_mmap_page *pc) | |
153 | { | |
154 | int ret; | |
155 | ||
156 | if (!pc) | |
157 | return; | |
158 | ret = munmap(pc, sizeof(struct perf_event_mmap_page)); | |
159 | if (ret < 0) { | |
160 | PERROR("Error in munmap"); | |
161 | abort(); | |
162 | } | |
163 | } | |
164 | ||
165 | static | |
166 | struct lttng_perf_counter_thread *alloc_perf_counter_thread(void) | |
167 | { | |
168 | struct lttng_perf_counter_thread *perf_thread; | |
169 | sigset_t newmask, oldmask; | |
170 | int ret; | |
171 | ||
172 | ret = sigfillset(&newmask); | |
173 | if (ret) | |
174 | abort(); | |
175 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); | |
176 | if (ret) | |
177 | abort(); | |
178 | /* Check again with signals disabled */ | |
179 | perf_thread = pthread_getspecific(perf_counter_key); | |
180 | if (perf_thread) | |
181 | goto skip; | |
182 | perf_thread = zmalloc(sizeof(*perf_thread)); | |
183 | if (!perf_thread) | |
184 | abort(); | |
185 | CDS_INIT_LIST_HEAD(&perf_thread->rcu_field_list); | |
186 | ret = pthread_setspecific(perf_counter_key, perf_thread); | |
187 | if (ret) | |
188 | abort(); | |
189 | skip: | |
190 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
191 | if (ret) | |
192 | abort(); | |
193 | return perf_thread; | |
194 | } | |
195 | ||
196 | static | |
197 | struct lttng_perf_counter_thread_field * | |
198 | add_thread_field(struct lttng_perf_counter_field *perf_field, | |
199 | struct lttng_perf_counter_thread *perf_thread) | |
200 | { | |
201 | struct lttng_perf_counter_thread_field *thread_field; | |
202 | sigset_t newmask, oldmask; | |
203 | int ret; | |
204 | ||
205 | ret = sigfillset(&newmask); | |
206 | if (ret) | |
207 | abort(); | |
208 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); | |
209 | if (ret) | |
210 | abort(); | |
211 | /* Check again with signals disabled */ | |
212 | cds_list_for_each_entry_rcu(thread_field, &perf_thread->rcu_field_list, | |
213 | rcu_field_node) { | |
214 | if (thread_field->field == perf_field) | |
215 | goto skip; | |
216 | } | |
217 | thread_field = zmalloc(sizeof(*thread_field)); | |
218 | if (!thread_field) | |
219 | abort(); | |
220 | thread_field->field = perf_field; | |
221 | thread_field->pc = setup_perf(&perf_field->attr); | |
222 | /* Note: thread_field->pc can be NULL if setup_perf() fails. */ | |
223 | ust_lock_nocheck(); | |
224 | cds_list_add_rcu(&thread_field->rcu_field_node, | |
225 | &perf_thread->rcu_field_list); | |
226 | cds_list_add(&thread_field->thread_field_node, | |
227 | &perf_field->thread_field_list); | |
228 | ust_unlock(); | |
229 | skip: | |
230 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
231 | if (ret) | |
232 | abort(); | |
233 | return thread_field; | |
234 | } | |
235 | ||
236 | static | |
237 | struct lttng_perf_counter_thread_field * | |
238 | get_thread_field(struct lttng_perf_counter_field *field) | |
239 | { | |
240 | struct lttng_perf_counter_thread *perf_thread; | |
241 | struct lttng_perf_counter_thread_field *thread_field; | |
242 | ||
243 | perf_thread = pthread_getspecific(perf_counter_key); | |
244 | if (!perf_thread) | |
245 | perf_thread = alloc_perf_counter_thread(); | |
246 | cds_list_for_each_entry_rcu(thread_field, &perf_thread->rcu_field_list, | |
247 | rcu_field_node) { | |
248 | if (thread_field->field == field) | |
249 | return thread_field; | |
250 | } | |
251 | /* perf_counter_thread_field not found, need to add one */ | |
252 | return add_thread_field(field, perf_thread); | |
253 | } | |
254 | ||
255 | static | |
256 | uint64_t wrapper_perf_counter_read(struct lttng_ctx_field *field) | |
257 | { | |
258 | struct lttng_perf_counter_field *perf_field; | |
259 | struct lttng_perf_counter_thread_field *perf_thread_field; | |
260 | ||
261 | perf_field = field->u.perf_counter; | |
262 | perf_thread_field = get_thread_field(perf_field); | |
263 | return read_perf_counter(perf_thread_field->pc); | |
264 | } | |
265 | ||
266 | static | |
267 | void perf_counter_record(struct lttng_ctx_field *field, | |
268 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
269 | struct lttng_channel *chan) | |
270 | { | |
271 | uint64_t value; | |
272 | ||
273 | value = wrapper_perf_counter_read(field); | |
274 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(value)); | |
275 | chan->ops->event_write(ctx, &value, sizeof(value)); | |
276 | } | |
277 | ||
278 | static | |
279 | void perf_counter_get_value(struct lttng_ctx_field *field, | |
280 | union lttng_ctx_value *value) | |
281 | { | |
282 | uint64_t v; | |
283 | ||
284 | v = wrapper_perf_counter_read(field); | |
285 | value->s64 = v; | |
286 | } | |
287 | ||
288 | /* Called with UST lock held */ | |
289 | static | |
290 | void lttng_destroy_perf_thread_field( | |
291 | struct lttng_perf_counter_thread_field *thread_field) | |
292 | { | |
293 | unmap_perf_page(thread_field->pc); | |
294 | cds_list_del_rcu(&thread_field->rcu_field_node); | |
295 | cds_list_del(&thread_field->thread_field_node); | |
296 | free(thread_field); | |
297 | } | |
298 | ||
299 | static | |
300 | void lttng_destroy_perf_thread_key(void *_key) | |
301 | { | |
302 | struct lttng_perf_counter_thread *perf_thread = _key; | |
303 | struct lttng_perf_counter_thread_field *pos, *p; | |
304 | ||
305 | ust_lock_nocheck(); | |
306 | cds_list_for_each_entry_safe(pos, p, &perf_thread->rcu_field_list, | |
307 | rcu_field_node) | |
308 | lttng_destroy_perf_thread_field(pos); | |
309 | ust_unlock(); | |
310 | free(perf_thread); | |
311 | } | |
312 | ||
313 | /* Called with UST lock held */ | |
314 | static | |
315 | void lttng_destroy_perf_counter_field(struct lttng_ctx_field *field) | |
316 | { | |
317 | struct lttng_perf_counter_field *perf_field; | |
318 | struct lttng_perf_counter_thread_field *pos, *p; | |
319 | ||
320 | free((char *) field->event_field.name); | |
321 | perf_field = field->u.perf_counter; | |
322 | /* | |
323 | * This put is performed when no threads can concurrently | |
324 | * perform a "get" concurrently, thanks to urcu-bp grace | |
325 | * period. | |
326 | */ | |
327 | cds_list_for_each_entry_safe(pos, p, &perf_field->thread_field_list, | |
328 | thread_field_node) | |
329 | lttng_destroy_perf_thread_field(pos); | |
330 | free(perf_field); | |
331 | } | |
332 | ||
333 | /* Called with UST lock held */ | |
334 | int lttng_add_perf_counter_to_ctx(uint32_t type, | |
335 | uint64_t config, | |
336 | const char *name, | |
337 | struct lttng_ctx **ctx) | |
338 | { | |
339 | struct lttng_ctx_field *field; | |
340 | struct lttng_perf_counter_field *perf_field; | |
341 | struct perf_event_mmap_page *tmp_pc; | |
342 | char *name_alloc; | |
343 | int ret; | |
344 | ||
345 | name_alloc = strdup(name); | |
346 | if (!name_alloc) { | |
347 | ret = -ENOMEM; | |
348 | goto name_alloc_error; | |
349 | } | |
350 | perf_field = zmalloc(sizeof(*perf_field)); | |
351 | if (!perf_field) { | |
352 | ret = -ENOMEM; | |
353 | goto perf_field_alloc_error; | |
354 | } | |
355 | field = lttng_append_context(ctx); | |
356 | if (!field) { | |
357 | ret = -ENOMEM; | |
358 | goto append_context_error; | |
359 | } | |
360 | if (lttng_find_context(*ctx, name_alloc)) { | |
361 | ret = -EEXIST; | |
362 | goto find_error; | |
363 | } | |
364 | ||
365 | field->destroy = lttng_destroy_perf_counter_field; | |
366 | ||
367 | field->event_field.name = name_alloc; | |
368 | field->event_field.type.atype = atype_integer; | |
369 | field->event_field.type.u.basic.integer.size = | |
370 | sizeof(uint64_t) * CHAR_BIT; | |
371 | field->event_field.type.u.basic.integer.alignment = | |
372 | lttng_alignof(uint64_t) * CHAR_BIT; | |
373 | field->event_field.type.u.basic.integer.signedness = | |
374 | lttng_is_signed_type(uint64_t); | |
375 | field->event_field.type.u.basic.integer.reverse_byte_order = 0; | |
376 | field->event_field.type.u.basic.integer.base = 10; | |
377 | field->event_field.type.u.basic.integer.encoding = lttng_encode_none; | |
378 | field->get_size = perf_counter_get_size; | |
379 | field->record = perf_counter_record; | |
380 | field->get_value = perf_counter_get_value; | |
381 | ||
382 | perf_field->attr.type = type; | |
383 | perf_field->attr.config = config; | |
384 | perf_field->attr.exclude_kernel = 1; | |
385 | CDS_INIT_LIST_HEAD(&perf_field->thread_field_list); | |
386 | field->u.perf_counter = perf_field; | |
387 | ||
388 | /* Ensure that this perf counter can be used in this process. */ | |
389 | tmp_pc = setup_perf(&perf_field->attr); | |
390 | if (!tmp_pc) { | |
391 | ret = -ENODEV; | |
392 | goto setup_error; | |
393 | } | |
394 | unmap_perf_page(tmp_pc); | |
395 | ||
396 | /* | |
397 | * Contexts can only be added before tracing is started, so we | |
398 | * don't have to synchronize against concurrent threads using | |
399 | * the field here. | |
400 | */ | |
401 | ||
402 | return 0; | |
403 | ||
404 | setup_error: | |
405 | find_error: | |
406 | lttng_remove_context_field(ctx, field); | |
407 | append_context_error: | |
408 | free(perf_field); | |
409 | perf_field_alloc_error: | |
410 | free(name_alloc); | |
411 | name_alloc_error: | |
412 | return ret; | |
413 | } | |
414 | ||
415 | int lttng_perf_counter_init(void) | |
416 | { | |
417 | int ret; | |
418 | ||
419 | ret = pthread_key_create(&perf_counter_key, | |
420 | lttng_destroy_perf_thread_key); | |
421 | if (ret) | |
422 | ret = -ret; | |
423 | return ret; | |
424 | } | |
425 | ||
426 | void lttng_perf_counter_exit(void) | |
427 | { | |
428 | int ret; | |
429 | ||
430 | ret = pthread_key_delete(perf_counter_key); | |
431 | if (ret) { | |
432 | errno = ret; | |
433 | PERROR("Error in pthread_key_delete"); | |
434 | } | |
435 | } |