2 * lttng-context-perf-counters.c
4 * LTTng UST performance monitoring counters (perf-counters) integration.
6 * Copyright (C) 2009-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
23 #include <sys/types.h>
30 #include <sys/syscall.h>
31 #include <linux/perf_event.h>
32 #include <lttng/ust-events.h>
33 #include <lttng/ust-tracer.h>
34 #include <lttng/ringbuffer-config.h>
35 #include <urcu/system.h>
36 #include <urcu/arch.h>
37 #include <urcu/rculist.h>
40 #include <usterr-signal-safe.h>
42 #include "lttng-tracer-core.h"
45 * We use a global perf counter key and iterate on per-thread RCU lists
46 * of fields in the fast path, even though this is not strictly speaking
47 * what would provide the best fast-path complexity, to ensure teardown
48 * of sessions vs thread exit is handled racelessly.
50 * Updates and traversals of thread_list are protected by UST lock.
51 * Updates to rcu_field_list are protected by UST lock.
54 struct lttng_perf_counter_thread_field
{
55 struct lttng_perf_counter_field
*field
; /* Back reference */
56 struct perf_event_mmap_page
*pc
;
57 struct cds_list_head thread_field_node
; /* Per-field list of thread fields (node) */
58 struct cds_list_head rcu_field_node
; /* RCU per-thread list of fields (node) */
62 struct lttng_perf_counter_thread
{
63 struct cds_list_head rcu_field_list
; /* RCU per-thread list of fields */
66 struct lttng_perf_counter_field
{
67 struct perf_event_attr attr
;
68 struct cds_list_head thread_field_list
; /* Per-field list of thread fields */
71 static pthread_key_t perf_counter_key
;
74 size_t perf_counter_get_size(struct lttng_ctx_field
*field
, size_t offset
)
78 size
+= lib_ring_buffer_align(offset
, lttng_alignof(uint64_t));
79 size
+= sizeof(uint64_t);
84 uint64_t read_perf_counter_syscall(
85 struct lttng_perf_counter_thread_field
*thread_field
)
89 if (caa_unlikely(thread_field
->fd
< 0))
92 if (caa_unlikely(read(thread_field
->fd
, &count
, sizeof(count
))
99 #if defined(__x86_64__) || defined(__i386__)
102 uint64_t rdpmc(unsigned int counter
)
104 unsigned int low
, high
;
106 asm volatile("rdpmc" : "=a" (low
), "=d" (high
) : "c" (counter
));
108 return low
| ((uint64_t) high
) << 32;
112 uint64_t arch_read_perf_counter(
113 struct lttng_perf_counter_thread_field
*thread_field
)
117 struct perf_event_mmap_page
*pc
= thread_field
->pc
;
119 if (caa_unlikely(!pc
))
123 seq
= CMM_LOAD_SHARED(pc
->lock
);
127 if (caa_likely(pc
->cap_user_rdpmc
&& idx
)) {
130 pmcval
= rdpmc(idx
- 1);
131 /* Sign-extend the pmc register result. */
132 pmcval
<<= 64 - pc
->pmc_width
;
133 pmcval
>>= 64 - pc
->pmc_width
;
134 count
= pc
->offset
+ pmcval
;
136 /* Fall-back on system call if rdpmc cannot be used. */
137 return read_perf_counter_syscall(thread_field
);
140 } while (CMM_LOAD_SHARED(pc
->lock
) != seq
);
146 int arch_perf_keep_fd(struct lttng_perf_counter_thread_field
*thread_field
)
148 struct perf_event_mmap_page
*pc
= thread_field
->pc
;
152 return !pc
->cap_user_rdpmc
;
157 /* Generic (slow) implementation using a read system call. */
159 uint64_t arch_read_perf_counter(
160 struct lttng_perf_counter_thread_field
*thread_field
)
162 return read_perf_counter_syscall(thread_field
);
166 int arch_perf_keep_fd(struct lttng_perf_counter_thread_field
*thread_field
)
174 int sys_perf_event_open(struct perf_event_attr
*attr
,
175 pid_t pid
, int cpu
, int group_fd
,
178 return syscall(SYS_perf_event_open
, attr
, pid
, cpu
,
183 int open_perf_fd(struct perf_event_attr
*attr
)
187 fd
= sys_perf_event_open(attr
, 0, -1, -1, 0);
195 void close_perf_fd(int fd
)
204 perror("Error closing LTTng-UST perf memory mapping FD");
209 struct perf_event_mmap_page
*setup_perf(
210 struct lttng_perf_counter_thread_field
*thread_field
)
214 perf_addr
= mmap(NULL
, sizeof(struct perf_event_mmap_page
),
215 PROT_READ
, MAP_SHARED
, thread_field
->fd
, 0);
216 if (perf_addr
== MAP_FAILED
)
219 if (!arch_perf_keep_fd(thread_field
)) {
220 close_perf_fd(thread_field
->fd
);
221 thread_field
->fd
= -1;
228 void unmap_perf_page(struct perf_event_mmap_page
*pc
)
234 ret
= munmap(pc
, sizeof(struct perf_event_mmap_page
));
236 PERROR("Error in munmap");
242 struct lttng_perf_counter_thread
*alloc_perf_counter_thread(void)
244 struct lttng_perf_counter_thread
*perf_thread
;
245 sigset_t newmask
, oldmask
;
248 ret
= sigfillset(&newmask
);
251 ret
= pthread_sigmask(SIG_BLOCK
, &newmask
, &oldmask
);
254 /* Check again with signals disabled */
255 perf_thread
= pthread_getspecific(perf_counter_key
);
258 perf_thread
= zmalloc(sizeof(*perf_thread
));
261 CDS_INIT_LIST_HEAD(&perf_thread
->rcu_field_list
);
262 ret
= pthread_setspecific(perf_counter_key
, perf_thread
);
266 ret
= pthread_sigmask(SIG_SETMASK
, &oldmask
, NULL
);
273 struct lttng_perf_counter_thread_field
*
274 add_thread_field(struct lttng_perf_counter_field
*perf_field
,
275 struct lttng_perf_counter_thread
*perf_thread
)
277 struct lttng_perf_counter_thread_field
*thread_field
;
278 sigset_t newmask
, oldmask
;
281 ret
= sigfillset(&newmask
);
284 ret
= pthread_sigmask(SIG_BLOCK
, &newmask
, &oldmask
);
287 /* Check again with signals disabled */
288 cds_list_for_each_entry_rcu(thread_field
, &perf_thread
->rcu_field_list
,
290 if (thread_field
->field
== perf_field
)
293 thread_field
= zmalloc(sizeof(*thread_field
));
296 thread_field
->field
= perf_field
;
297 thread_field
->fd
= open_perf_fd(&perf_field
->attr
);
298 if (thread_field
->fd
>= 0)
299 thread_field
->pc
= setup_perf(thread_field
);
301 * Note: thread_field->pc can be NULL if setup_perf() fails.
302 * Also, thread_field->fd can be -1 if open_perf_fd() fails.
305 cds_list_add_rcu(&thread_field
->rcu_field_node
,
306 &perf_thread
->rcu_field_list
);
307 cds_list_add(&thread_field
->thread_field_node
,
308 &perf_field
->thread_field_list
);
311 ret
= pthread_sigmask(SIG_SETMASK
, &oldmask
, NULL
);
318 struct lttng_perf_counter_thread_field
*
319 get_thread_field(struct lttng_perf_counter_field
*field
)
321 struct lttng_perf_counter_thread
*perf_thread
;
322 struct lttng_perf_counter_thread_field
*thread_field
;
324 perf_thread
= pthread_getspecific(perf_counter_key
);
326 perf_thread
= alloc_perf_counter_thread();
327 cds_list_for_each_entry_rcu(thread_field
, &perf_thread
->rcu_field_list
,
329 if (thread_field
->field
== field
)
332 /* perf_counter_thread_field not found, need to add one */
333 return add_thread_field(field
, perf_thread
);
337 uint64_t wrapper_perf_counter_read(struct lttng_ctx_field
*field
)
339 struct lttng_perf_counter_field
*perf_field
;
340 struct lttng_perf_counter_thread_field
*perf_thread_field
;
342 perf_field
= field
->u
.perf_counter
;
343 perf_thread_field
= get_thread_field(perf_field
);
344 return arch_read_perf_counter(perf_thread_field
);
348 void perf_counter_record(struct lttng_ctx_field
*field
,
349 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
350 struct lttng_channel
*chan
)
354 value
= wrapper_perf_counter_read(field
);
355 lib_ring_buffer_align_ctx(ctx
, lttng_alignof(value
));
356 chan
->ops
->event_write(ctx
, &value
, sizeof(value
));
360 void perf_counter_get_value(struct lttng_ctx_field
*field
,
361 struct lttng_ctx_value
*value
)
365 v
= wrapper_perf_counter_read(field
);
369 /* Called with UST lock held */
371 void lttng_destroy_perf_thread_field(
372 struct lttng_perf_counter_thread_field
*thread_field
)
374 close_perf_fd(thread_field
->fd
);
375 unmap_perf_page(thread_field
->pc
);
376 cds_list_del_rcu(&thread_field
->rcu_field_node
);
377 cds_list_del(&thread_field
->thread_field_node
);
382 void lttng_destroy_perf_thread_key(void *_key
)
384 struct lttng_perf_counter_thread
*perf_thread
= _key
;
385 struct lttng_perf_counter_thread_field
*pos
, *p
;
388 cds_list_for_each_entry_safe(pos
, p
, &perf_thread
->rcu_field_list
,
390 lttng_destroy_perf_thread_field(pos
);
395 /* Called with UST lock held */
397 void lttng_destroy_perf_counter_field(struct lttng_ctx_field
*field
)
399 struct lttng_perf_counter_field
*perf_field
;
400 struct lttng_perf_counter_thread_field
*pos
, *p
;
402 free((char *) field
->event_field
.name
);
403 perf_field
= field
->u
.perf_counter
;
405 * This put is performed when no threads can concurrently
406 * perform a "get" concurrently, thanks to urcu-bp grace
409 cds_list_for_each_entry_safe(pos
, p
, &perf_field
->thread_field_list
,
411 lttng_destroy_perf_thread_field(pos
);
415 #ifdef __ARM_ARCH_7A__
418 int perf_get_exclude_kernel(void)
423 #else /* __ARM_ARCH_7A__ */
426 int perf_get_exclude_kernel(void)
431 #endif /* __ARM_ARCH_7A__ */
433 /* Called with UST lock held */
434 int lttng_add_perf_counter_to_ctx(uint32_t type
,
437 struct lttng_ctx
**ctx
)
439 struct lttng_ctx_field
*field
;
440 struct lttng_perf_counter_field
*perf_field
;
444 name_alloc
= strdup(name
);
447 goto name_alloc_error
;
449 perf_field
= zmalloc(sizeof(*perf_field
));
452 goto perf_field_alloc_error
;
454 field
= lttng_append_context(ctx
);
457 goto append_context_error
;
459 if (lttng_find_context(*ctx
, name_alloc
)) {
464 field
->destroy
= lttng_destroy_perf_counter_field
;
466 field
->event_field
.name
= name_alloc
;
467 field
->event_field
.type
.atype
= atype_integer
;
468 field
->event_field
.type
.u
.basic
.integer
.size
=
469 sizeof(uint64_t) * CHAR_BIT
;
470 field
->event_field
.type
.u
.basic
.integer
.alignment
=
471 lttng_alignof(uint64_t) * CHAR_BIT
;
472 field
->event_field
.type
.u
.basic
.integer
.signedness
=
473 lttng_is_signed_type(uint64_t);
474 field
->event_field
.type
.u
.basic
.integer
.reverse_byte_order
= 0;
475 field
->event_field
.type
.u
.basic
.integer
.base
= 10;
476 field
->event_field
.type
.u
.basic
.integer
.encoding
= lttng_encode_none
;
477 field
->get_size
= perf_counter_get_size
;
478 field
->record
= perf_counter_record
;
479 field
->get_value
= perf_counter_get_value
;
481 perf_field
->attr
.type
= type
;
482 perf_field
->attr
.config
= config
;
483 perf_field
->attr
.exclude_kernel
= perf_get_exclude_kernel();
484 CDS_INIT_LIST_HEAD(&perf_field
->thread_field_list
);
485 field
->u
.perf_counter
= perf_field
;
487 /* Ensure that this perf counter can be used in this process. */
488 ret
= open_perf_fd(&perf_field
->attr
);
496 * Contexts can only be added before tracing is started, so we
497 * don't have to synchronize against concurrent threads using
501 lttng_context_update(*ctx
);
506 lttng_remove_context_field(ctx
, field
);
507 append_context_error
:
509 perf_field_alloc_error
:
515 int lttng_perf_counter_init(void)
519 ret
= pthread_key_create(&perf_counter_key
,
520 lttng_destroy_perf_thread_key
);
526 void lttng_perf_counter_exit(void)
530 ret
= pthread_key_delete(perf_counter_key
);
533 PERROR("Error in pthread_key_delete");