2 * ring_buffer_backend.c
4 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; only
9 * version 2.1 of the License.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #include <urcu/arch.h>
26 #include <lttng/ringbuffer-config.h>
34 * lib_ring_buffer_backend_allocate - allocate a channel buffer
35 * @config: ring buffer instance configuration
36 * @buf: the buffer struct
37 * @size: total size of the buffer
38 * @num_subbuf: number of subbuffers
39 * @extra_reader_sb: need extra subbuffer for reader
42 int lib_ring_buffer_backend_allocate(const struct lttng_ust_lib_ring_buffer_config
*config
,
43 struct lttng_ust_lib_ring_buffer_backend
*bufb
,
44 size_t size
, size_t num_subbuf
,
46 struct lttng_ust_shm_handle
*handle
,
47 struct shm_object
*shmobj
)
49 struct channel_backend
*chanb
;
50 unsigned long subbuf_size
, mmap_offset
= 0;
51 unsigned long num_subbuf_alloc
;
55 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
59 subbuf_size
= chanb
->subbuf_size
;
60 num_subbuf_alloc
= num_subbuf
;
65 page_size
= sysconf(_SC_PAGE_SIZE
);
70 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp
));
71 set_shmp(bufb
->array
, zalloc_shm(shmobj
,
72 sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp
) * num_subbuf_alloc
));
73 if (caa_unlikely(!shmp(handle
, bufb
->array
)))
77 * This is the largest element (the buffer pages) which needs to
78 * be aligned on page size.
80 align_shm(shmobj
, page_size
);
81 set_shmp(bufb
->memory_map
, zalloc_shm(shmobj
,
82 subbuf_size
* num_subbuf_alloc
));
83 if (caa_unlikely(!shmp(handle
, bufb
->memory_map
)))
84 goto memory_map_error
;
86 /* Allocate backend pages array elements */
87 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
88 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages
));
89 set_shmp(shmp_index(handle
, bufb
->array
, i
)->shmp
,
91 sizeof(struct lttng_ust_lib_ring_buffer_backend_pages
)));
92 if (!shmp(handle
, shmp_index(handle
, bufb
->array
, i
)->shmp
))
96 /* Allocate write-side subbuffer table */
97 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer
));
98 set_shmp(bufb
->buf_wsb
, zalloc_shm(shmobj
,
99 sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer
)
101 if (caa_unlikely(!shmp(handle
, bufb
->buf_wsb
)))
104 for (i
= 0; i
< num_subbuf
; i
++) {
105 struct lttng_ust_lib_ring_buffer_backend_subbuffer
*sb
;
107 sb
= shmp_index(handle
, bufb
->buf_wsb
, i
);
110 sb
->id
= subbuffer_id(config
, 0, 1, i
);
113 /* Assign read-side subbuffer table */
115 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1,
116 num_subbuf_alloc
- 1);
118 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1, 0);
120 /* Allocate subbuffer packet counter table */
121 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer
));
122 set_shmp(bufb
->buf_cnt
, zalloc_shm(shmobj
,
123 sizeof(struct lttng_ust_lib_ring_buffer_backend_counts
)
125 if (caa_unlikely(!shmp(handle
, bufb
->buf_cnt
)))
128 /* Assign pages to page index */
129 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
130 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*sbp
;
131 struct lttng_ust_lib_ring_buffer_backend_pages
*pages
;
134 ref
.index
= bufb
->memory_map
._ref
.index
;
135 ref
.offset
= bufb
->memory_map
._ref
.offset
;
136 ref
.offset
+= i
* subbuf_size
;
138 sbp
= shmp_index(handle
, bufb
->array
, i
);
141 pages
= shmp(handle
, sbp
->shmp
);
144 set_shmp(pages
->p
, ref
);
145 if (config
->output
== RING_BUFFER_MMAP
) {
146 pages
->mmap_offset
= mmap_offset
;
147 mmap_offset
+= subbuf_size
;
153 /* bufb->buf_wsb will be freed by shm teardown */
155 /* bufb->array[i] will be freed by shm teardown */
157 /* bufb->array will be freed by shm teardown */
163 int lib_ring_buffer_backend_create(struct lttng_ust_lib_ring_buffer_backend
*bufb
,
164 struct channel_backend
*chanb
, int cpu
,
165 struct lttng_ust_shm_handle
*handle
,
166 struct shm_object
*shmobj
)
168 const struct lttng_ust_lib_ring_buffer_config
*config
= &chanb
->config
;
170 set_shmp(bufb
->chan
, handle
->chan
._ref
);
173 return lib_ring_buffer_backend_allocate(config
, bufb
, chanb
->buf_size
,
175 chanb
->extra_reader_sb
,
179 void lib_ring_buffer_backend_reset(struct lttng_ust_lib_ring_buffer_backend
*bufb
,
180 struct lttng_ust_shm_handle
*handle
)
182 struct channel_backend
*chanb
;
183 const struct lttng_ust_lib_ring_buffer_config
*config
;
184 unsigned long num_subbuf_alloc
;
187 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
190 config
= &chanb
->config
;
192 num_subbuf_alloc
= chanb
->num_subbuf
;
193 if (chanb
->extra_reader_sb
)
196 for (i
= 0; i
< chanb
->num_subbuf
; i
++) {
197 struct lttng_ust_lib_ring_buffer_backend_subbuffer
*sb
;
199 sb
= shmp_index(handle
, bufb
->buf_wsb
, i
);
202 sb
->id
= subbuffer_id(config
, 0, 1, i
);
204 if (chanb
->extra_reader_sb
)
205 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1,
206 num_subbuf_alloc
- 1);
208 bufb
->buf_rsb
.id
= subbuffer_id(config
, 0, 1, 0);
210 for (i
= 0; i
< num_subbuf_alloc
; i
++) {
211 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*sbp
;
212 struct lttng_ust_lib_ring_buffer_backend_pages
*pages
;
214 sbp
= shmp_index(handle
, bufb
->array
, i
);
217 pages
= shmp(handle
, sbp
->shmp
);
220 /* Don't reset mmap_offset */
221 v_set(config
, &pages
->records_commit
, 0);
222 v_set(config
, &pages
->records_unread
, 0);
223 pages
->data_size
= 0;
224 /* Don't reset backend page and virt addresses */
226 /* Don't reset num_pages_per_subbuf, cpu, allocated */
227 v_set(config
, &bufb
->records_read
, 0);
231 * The frontend is responsible for also calling ring_buffer_backend_reset for
232 * each buffer when calling channel_backend_reset.
234 void channel_backend_reset(struct channel_backend
*chanb
)
236 struct channel
*chan
= caa_container_of(chanb
, struct channel
, backend
);
237 const struct lttng_ust_lib_ring_buffer_config
*config
= &chanb
->config
;
240 * Don't reset buf_size, subbuf_size, subbuf_size_order,
241 * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf,
242 * priv, notifiers, config, cpumask and name.
244 chanb
->start_tsc
= config
->cb
.ring_buffer_clock_read(chan
);
248 * channel_backend_init - initialize a channel backend
249 * @chanb: channel backend
250 * @name: channel name
251 * @config: client ring buffer configuration
252 * @parent: dentry of parent directory, %NULL for root directory
253 * @subbuf_size: size of sub-buffers (> page size, power of 2)
254 * @num_subbuf: number of sub-buffers (power of 2)
255 * @lttng_ust_shm_handle: shared memory handle
256 * @stream_fds: stream file descriptors.
258 * Returns channel pointer if successful, %NULL otherwise.
260 * Creates per-cpu channel buffers using the sizes and attributes
261 * specified. The created channel buffer files will be named
262 * name_0...name_N-1. File permissions will be %S_IRUSR.
264 * Called with CPU hotplug disabled.
266 int channel_backend_init(struct channel_backend
*chanb
,
268 const struct lttng_ust_lib_ring_buffer_config
*config
,
269 size_t subbuf_size
, size_t num_subbuf
,
270 struct lttng_ust_shm_handle
*handle
,
271 const int *stream_fds
)
273 struct channel
*chan
= caa_container_of(chanb
, struct channel
, backend
);
276 size_t shmsize
= 0, num_subbuf_alloc
;
282 page_size
= sysconf(_SC_PAGE_SIZE
);
283 if (page_size
<= 0) {
286 /* Check that the subbuffer size is larger than a page. */
287 if (subbuf_size
< page_size
)
291 * Make sure the number of subbuffers and subbuffer size are
292 * power of 2, and nonzero.
294 if (!subbuf_size
|| (subbuf_size
& (subbuf_size
- 1)))
296 if (!num_subbuf
|| (num_subbuf
& (num_subbuf
- 1)))
299 * Overwrite mode buffers require at least 2 subbuffers per
302 if (config
->mode
== RING_BUFFER_OVERWRITE
&& num_subbuf
< 2)
305 ret
= subbuffer_id_check_index(config
, num_subbuf
);
309 chanb
->buf_size
= num_subbuf
* subbuf_size
;
310 chanb
->subbuf_size
= subbuf_size
;
311 chanb
->buf_size_order
= get_count_order(chanb
->buf_size
);
312 chanb
->subbuf_size_order
= get_count_order(subbuf_size
);
313 chanb
->num_subbuf_order
= get_count_order(num_subbuf
);
314 chanb
->extra_reader_sb
=
315 (config
->mode
== RING_BUFFER_OVERWRITE
) ? 1 : 0;
316 chanb
->num_subbuf
= num_subbuf
;
317 strncpy(chanb
->name
, name
, NAME_MAX
);
318 chanb
->name
[NAME_MAX
- 1] = '\0';
319 memcpy(&chanb
->config
, config
, sizeof(*config
));
321 /* Per-cpu buffer size: control (prior to backend) */
322 shmsize
= offset_align(shmsize
, __alignof__(struct lttng_ust_lib_ring_buffer
));
323 shmsize
+= sizeof(struct lttng_ust_lib_ring_buffer
);
325 /* Per-cpu buffer size: backend */
326 /* num_subbuf + 1 is the worse case */
327 num_subbuf_alloc
= num_subbuf
+ 1;
328 shmsize
+= offset_align(shmsize
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp
));
329 shmsize
+= sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp
) * num_subbuf_alloc
;
330 shmsize
+= offset_align(shmsize
, page_size
);
331 shmsize
+= subbuf_size
* num_subbuf_alloc
;
332 shmsize
+= offset_align(shmsize
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages
));
333 shmsize
+= sizeof(struct lttng_ust_lib_ring_buffer_backend_pages
) * num_subbuf_alloc
;
334 shmsize
+= offset_align(shmsize
, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer
));
335 shmsize
+= sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer
) * num_subbuf
;
336 /* Per-cpu buffer size: control (after backend) */
337 shmsize
+= offset_align(shmsize
, __alignof__(struct commit_counters_hot
));
338 shmsize
+= sizeof(struct commit_counters_hot
) * num_subbuf
;
339 shmsize
+= offset_align(shmsize
, __alignof__(struct commit_counters_cold
));
340 shmsize
+= sizeof(struct commit_counters_cold
) * num_subbuf
;
342 if (config
->alloc
== RING_BUFFER_ALLOC_PER_CPU
) {
343 struct lttng_ust_lib_ring_buffer
*buf
;
345 * We need to allocate for all possible cpus.
347 for_each_possible_cpu(i
) {
348 struct shm_object
*shmobj
;
350 shmobj
= shm_object_table_alloc(handle
->table
, shmsize
,
351 SHM_OBJECT_SHM
, stream_fds
[i
]);
354 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer
));
355 set_shmp(chanb
->buf
[i
].shmp
, zalloc_shm(shmobj
, sizeof(struct lttng_ust_lib_ring_buffer
)));
356 buf
= shmp(handle
, chanb
->buf
[i
].shmp
);
359 set_shmp(buf
->self
, chanb
->buf
[i
].shmp
._ref
);
360 ret
= lib_ring_buffer_create(buf
, chanb
, i
,
363 goto free_bufs
; /* cpu hotplug locked */
366 struct shm_object
*shmobj
;
367 struct lttng_ust_lib_ring_buffer
*buf
;
369 shmobj
= shm_object_table_alloc(handle
->table
, shmsize
,
370 SHM_OBJECT_SHM
, stream_fds
[0]);
373 align_shm(shmobj
, __alignof__(struct lttng_ust_lib_ring_buffer
));
374 set_shmp(chanb
->buf
[0].shmp
, zalloc_shm(shmobj
, sizeof(struct lttng_ust_lib_ring_buffer
)));
375 buf
= shmp(handle
, chanb
->buf
[0].shmp
);
378 set_shmp(buf
->self
, chanb
->buf
[0].shmp
._ref
);
379 ret
= lib_ring_buffer_create(buf
, chanb
, -1,
384 chanb
->start_tsc
= config
->cb
.ring_buffer_clock_read(chan
);
389 /* We only free the buffer data upon shm teardown */
395 * channel_backend_free - destroy the channel
398 * Destroy all channel buffers and frees the channel.
400 void channel_backend_free(struct channel_backend
*chanb
,
401 struct lttng_ust_shm_handle
*handle
)
403 /* SHM teardown takes care of everything */
407 * lib_ring_buffer_read - read data from ring_buffer_buffer.
408 * @bufb : buffer backend
409 * @offset : offset within the buffer
410 * @dest : destination address
411 * @len : length to copy to destination
413 * Should be protected by get_subbuf/put_subbuf.
414 * Returns the length copied.
416 size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend
*bufb
, size_t offset
,
417 void *dest
, size_t len
, struct lttng_ust_shm_handle
*handle
)
419 struct channel_backend
*chanb
;
420 const struct lttng_ust_lib_ring_buffer_config
*config
;
422 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*rpages
;
423 unsigned long sb_bindex
, id
;
426 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
429 config
= &chanb
->config
;
431 offset
&= chanb
->buf_size
- 1;
433 if (caa_unlikely(!len
))
435 id
= bufb
->buf_rsb
.id
;
436 sb_bindex
= subbuffer_id_get_index(config
, id
);
437 rpages
= shmp_index(handle
, bufb
->array
, sb_bindex
);
439 * Underlying layer should never ask for reads across
442 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
443 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
444 && subbuffer_id_is_noref(config
, id
));
445 src
= shmp_index(handle
, shmp(handle
, rpages
->shmp
)->p
,
446 offset
& (chanb
->subbuf_size
- 1));
447 if (caa_unlikely(!src
))
449 memcpy(dest
, src
, len
);
454 * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer.
455 * @bufb : buffer backend
456 * @offset : offset within the buffer
457 * @dest : destination address
458 * @len : destination's length
460 * Return string's length, or -EINVAL on error.
461 * Should be protected by get_subbuf/put_subbuf.
462 * Destination length should be at least 1 to hold '\0'.
464 int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend
*bufb
, size_t offset
,
465 void *dest
, size_t len
, struct lttng_ust_shm_handle
*handle
)
467 struct channel_backend
*chanb
;
468 const struct lttng_ust_lib_ring_buffer_config
*config
;
469 ssize_t string_len
, orig_offset
;
471 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*rpages
;
472 unsigned long sb_bindex
, id
;
474 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
477 config
= &chanb
->config
;
478 if (caa_unlikely(!len
))
480 offset
&= chanb
->buf_size
- 1;
481 orig_offset
= offset
;
482 id
= bufb
->buf_rsb
.id
;
483 sb_bindex
= subbuffer_id_get_index(config
, id
);
484 rpages
= shmp_index(handle
, bufb
->array
, sb_bindex
);
486 * Underlying layer should never ask for reads across
489 CHAN_WARN_ON(chanb
, offset
>= chanb
->buf_size
);
490 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
491 && subbuffer_id_is_noref(config
, id
));
492 str
= shmp_index(handle
, shmp(handle
, rpages
->shmp
)->p
, offset
& (chanb
->subbuf_size
- 1));
493 if (caa_unlikely(!str
))
495 string_len
= strnlen(str
, len
);
497 memcpy(dest
, str
, string_len
);
498 ((char *)dest
)[0] = 0;
500 return offset
- orig_offset
;
504 * lib_ring_buffer_read_offset_address - get address of a buffer location
505 * @bufb : buffer backend
506 * @offset : offset within the buffer.
508 * Return the address where a given offset is located (for read).
509 * Should be used to get the current subbuffer header pointer. Given we know
510 * it's never on a page boundary, it's safe to read/write directly
511 * from/to this address, as long as the read/write is never bigger than
514 void *lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend
*bufb
,
516 struct lttng_ust_shm_handle
*handle
)
518 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*rpages
;
519 struct channel_backend
*chanb
;
520 const struct lttng_ust_lib_ring_buffer_config
*config
;
521 unsigned long sb_bindex
, id
;
523 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
526 config
= &chanb
->config
;
527 offset
&= chanb
->buf_size
- 1;
528 id
= bufb
->buf_rsb
.id
;
529 sb_bindex
= subbuffer_id_get_index(config
, id
);
530 rpages
= shmp_index(handle
, bufb
->array
, sb_bindex
);
531 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
532 && subbuffer_id_is_noref(config
, id
));
533 return shmp_index(handle
, shmp(handle
, rpages
->shmp
)->p
, offset
& (chanb
->subbuf_size
- 1));
537 * lib_ring_buffer_offset_address - get address of a location within the buffer
538 * @bufb : buffer backend
539 * @offset : offset within the buffer.
541 * Return the address where a given offset is located.
542 * Should be used to get the current subbuffer header pointer. Given we know
543 * it's always at the beginning of a page, it's safe to write directly to this
544 * address, as long as the write is never bigger than a page size.
546 void *lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend
*bufb
,
548 struct lttng_ust_shm_handle
*handle
)
551 struct lttng_ust_lib_ring_buffer_backend_pages_shmp
*rpages
;
552 struct channel_backend
*chanb
;
553 const struct lttng_ust_lib_ring_buffer_config
*config
;
554 unsigned long sb_bindex
, id
;
555 struct lttng_ust_lib_ring_buffer_backend_subbuffer
*sb
;
557 chanb
= &shmp(handle
, bufb
->chan
)->backend
;
560 config
= &chanb
->config
;
561 offset
&= chanb
->buf_size
- 1;
562 sbidx
= offset
>> chanb
->subbuf_size_order
;
563 sb
= shmp_index(handle
, bufb
->buf_wsb
, sbidx
);
567 sb_bindex
= subbuffer_id_get_index(config
, id
);
568 rpages
= shmp_index(handle
, bufb
->array
, sb_bindex
);
569 CHAN_WARN_ON(chanb
, config
->mode
== RING_BUFFER_OVERWRITE
570 && subbuffer_id_is_noref(config
, id
));
571 return shmp_index(handle
, shmp(handle
, rpages
->shmp
)->p
, offset
& (chanb
->subbuf_size
- 1));