2 * SPDX-License-Identifier: MIT
4 * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 * Ring buffer configuration header. Note: after declaring the standard inline
7 * functions, clients should also include linux/ringbuffer/api.h.
10 #ifndef _LTTNG_RING_BUFFER_CONFIG_H
11 #define _LTTNG_RING_BUFFER_CONFIG_H
14 #include "lttng/ust-tracer.h"
17 #include <urcu/arch.h>
19 #include "lttng/align.h"
20 #include <lttng/ust-compiler.h>
22 struct lttng_ust_lib_ring_buffer
;
23 struct lttng_ust_lib_ring_buffer_channel
;
24 struct lttng_ust_lib_ring_buffer_config
;
25 struct lttng_ust_lib_ring_buffer_ctx
;
26 struct lttng_ust_shm_handle
;
29 * Ring buffer client callbacks. Only used by slow path, never on fast path.
30 * For the fast path, record_header_size(), ring_buffer_clock_read() should be
31 * provided as inline functions too. These may simply return 0 if not used by
34 struct lttng_ust_lib_ring_buffer_client_cb
{
35 /* Mandatory callbacks */
37 /* A static inline version is also required for fast path */
38 uint64_t (*ring_buffer_clock_read
) (struct lttng_ust_lib_ring_buffer_channel
*chan
);
39 size_t (*record_header_size
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
40 struct lttng_ust_lib_ring_buffer_channel
*chan
,
42 size_t *pre_header_padding
,
43 struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
46 /* Slow path only, at subbuffer switch */
47 size_t (*subbuffer_header_size
) (void);
48 void (*buffer_begin
) (struct lttng_ust_lib_ring_buffer
*buf
, uint64_t tsc
,
49 unsigned int subbuf_idx
,
50 struct lttng_ust_shm_handle
*handle
);
51 void (*buffer_end
) (struct lttng_ust_lib_ring_buffer
*buf
, uint64_t tsc
,
52 unsigned int subbuf_idx
, unsigned long data_size
,
53 struct lttng_ust_shm_handle
*handle
);
55 /* Optional callbacks (can be set to NULL) */
57 /* Called at buffer creation/finalize */
58 int (*buffer_create
) (struct lttng_ust_lib_ring_buffer
*buf
, void *priv
,
59 int cpu
, const char *name
,
60 struct lttng_ust_shm_handle
*handle
);
62 * Clients should guarantee that no new reader handle can be opened
65 void (*buffer_finalize
) (struct lttng_ust_lib_ring_buffer
*buf
,
67 struct lttng_ust_shm_handle
*handle
);
70 * Extract header length, payload length and timestamp from event
71 * record. Used by buffer iterators. Timestamp is only used by channel
74 void (*record_get
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
75 struct lttng_ust_lib_ring_buffer_channel
*chan
,
76 struct lttng_ust_lib_ring_buffer
*buf
,
77 size_t offset
, size_t *header_len
,
78 size_t *payload_len
, uint64_t *timestamp
,
79 struct lttng_ust_shm_handle
*handle
);
81 * Offset and size of content size field in client.
83 void (*content_size_field
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
84 size_t *offset
, size_t *length
);
85 void (*packet_size_field
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
86 size_t *offset
, size_t *length
);
90 * Ring buffer instance configuration.
92 * Declare as "static const" within the client object to ensure the inline fast
93 * paths can be optimized.
97 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
98 * Per-cpu buffers with per-cpu synchronization. Tracing must be performed
99 * with preemption disabled (lib_ring_buffer_get_cpu() and
100 * lib_ring_buffer_put_cpu()).
102 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
103 * Per-cpu buffer with global synchronization. Tracing can be performed with
104 * preemption enabled, statistically stays on the local buffers.
106 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
107 * Should only be used for buffers belonging to a single thread or protected
108 * by mutual exclusion by the client. Note that periodical sub-buffer switch
109 * should be disabled in this kind of configuration.
111 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
112 * Global shared buffer with global synchronization.
116 * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
117 * buffers and wake up readers if data is ready. Mainly useful for tracers which
118 * don't want to call into the wakeup code on the tracing path. Use in
119 * combination with "read_timer_interval" channel_create() argument.
121 * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
122 * ready to read. Lower latencies before the reader is woken up. Mainly suitable
125 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
126 * has the responsibility to perform wakeups.
128 #define LTTNG_UST_RING_BUFFER_CONFIG_PADDING 20
130 enum lttng_ust_lib_ring_buffer_alloc_types
{
131 RING_BUFFER_ALLOC_PER_CPU
,
132 RING_BUFFER_ALLOC_GLOBAL
,
135 enum lttng_ust_lib_ring_buffer_sync_types
{
136 RING_BUFFER_SYNC_PER_CPU
, /* Wait-free */
137 RING_BUFFER_SYNC_GLOBAL
, /* Lock-free */
140 enum lttng_ust_lib_ring_buffer_mode_types
{
141 RING_BUFFER_OVERWRITE
= 0, /* Overwrite when buffer full */
142 RING_BUFFER_DISCARD
= 1, /* Discard when buffer full */
145 enum lttng_ust_lib_ring_buffer_output_types
{
148 RING_BUFFER_READ
, /* TODO */
149 RING_BUFFER_ITERATOR
,
153 enum lttng_ust_lib_ring_buffer_backend_types
{
155 RING_BUFFER_VMAP
, /* TODO */
156 RING_BUFFER_STATIC
, /* TODO */
159 enum lttng_ust_lib_ring_buffer_oops_types
{
160 RING_BUFFER_NO_OOPS_CONSISTENCY
,
161 RING_BUFFER_OOPS_CONSISTENCY
,
164 enum lttng_ust_lib_ring_buffer_ipi_types
{
165 RING_BUFFER_IPI_BARRIER
,
166 RING_BUFFER_NO_IPI_BARRIER
,
169 enum lttng_ust_lib_ring_buffer_wakeup_types
{
170 RING_BUFFER_WAKEUP_BY_TIMER
, /* wake up performed by timer */
171 RING_BUFFER_WAKEUP_BY_WRITER
, /*
172 * writer wakes up reader,
178 struct lttng_ust_lib_ring_buffer_config
{
179 enum lttng_ust_lib_ring_buffer_alloc_types alloc
;
180 enum lttng_ust_lib_ring_buffer_sync_types sync
;
181 enum lttng_ust_lib_ring_buffer_mode_types mode
;
182 enum lttng_ust_lib_ring_buffer_output_types output
;
183 enum lttng_ust_lib_ring_buffer_backend_types backend
;
184 enum lttng_ust_lib_ring_buffer_oops_types oops
;
185 enum lttng_ust_lib_ring_buffer_ipi_types ipi
;
186 enum lttng_ust_lib_ring_buffer_wakeup_types wakeup
;
188 * tsc_bits: timestamp bits saved at each record.
189 * 0 and 64 disable the timestamp compression scheme.
191 unsigned int tsc_bits
;
192 struct lttng_ust_lib_ring_buffer_client_cb cb
;
194 * client_type is used by the consumer process (which is in a
195 * different address space) to lookup the appropriate client
196 * callbacks and update the cb pointers.
200 const struct lttng_ust_lib_ring_buffer_client_cb
*cb_ptr
;
201 char padding
[LTTNG_UST_RING_BUFFER_CONFIG_PADDING
];
205 * ring buffer context
207 * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
208 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
209 * lib_ring_buffer_write().
211 * IMPORTANT: this structure is part of the ABI between the probe and
212 * UST. Fields need to be only added at the end, never reordered, never
215 #define LTTNG_UST_RING_BUFFER_CTX_PADDING 64
216 struct lttng_ust_lib_ring_buffer_ctx
{
217 uint32_t struct_size
; /* Size of this structure. */
219 /* input received by lib_ring_buffer_reserve(), saved here. */
220 struct lttng_ust_lib_ring_buffer_channel
*chan
; /* channel */
221 void *priv
; /* client private data */
222 struct lttng_ust_shm_handle
*handle
; /* shared-memory handle */
223 size_t data_size
; /* size of payload */
224 int largest_align
; /*
225 * alignment of the largest element
228 int cpu
; /* processor id */
230 /* output from lib_ring_buffer_reserve() */
231 struct lttng_ust_lib_ring_buffer
*buf
; /*
232 * buffer corresponding to processor id
235 size_t slot_size
; /* size of the reserved slot */
236 unsigned long buf_offset
; /* offset following the record header */
237 unsigned long pre_offset
; /*
238 * Initial offset position _before_
239 * the record is written. Positioned
240 * prior to record header alignment
243 uint64_t tsc
; /* time-stamp counter value */
244 unsigned int rflags
; /* reservation flags */
245 void *ip
; /* caller ip address */
246 struct lttng_ust_lib_ring_buffer_backend_pages
*backend_pages
;
250 * lib_ring_buffer_ctx_init - initialize ring buffer context
251 * @ctx: ring buffer context to initialize
253 * @priv: client private data
254 * @data_size: size of record data payload
255 * @largest_align: largest alignment within data payload types
258 static inline lttng_ust_notrace
259 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
260 struct lttng_ust_lib_ring_buffer_channel
*chan
,
261 void *priv
, size_t data_size
, int largest_align
,
262 int cpu
, struct lttng_ust_shm_handle
*handle
);
264 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
265 struct lttng_ust_lib_ring_buffer_channel
*chan
,
266 void *priv
, size_t data_size
, int largest_align
,
267 int cpu
, struct lttng_ust_shm_handle
*handle
)
269 ctx
->struct_size
= sizeof(struct lttng_ust_lib_ring_buffer_ctx
);
272 ctx
->data_size
= data_size
;
273 ctx
->largest_align
= largest_align
;
276 ctx
->handle
= handle
;
283 * RING_BUFFER_RFLAG_FULL_TSC
285 * This flag is passed to record_header_size() and to the primitive used to
286 * write the record header. It indicates that the full 64-bit time value is
287 * needed in the record header. If this flag is not set, the record header needs
288 * only to contain "tsc_bits" bit of time value.
290 * Reservation flags can be added by the client, starting from
291 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
292 * record_header_size() to lib_ring_buffer_write_record_header().
294 #define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
295 #define RING_BUFFER_RFLAG_END (1U << 1)
298 * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
299 * compile-time. We have to duplicate the "config->align" information and the
300 * definition here because config->align is used both in the slow and fast
301 * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
303 #ifdef RING_BUFFER_ALIGN
305 # define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
308 * Calculate the offset needed to align the type.
309 * size_of_type must be non-zero.
311 static inline lttng_ust_notrace
312 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
);
314 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
316 return lttng_ust_offset_align(align_drift
, size_of_type
);
321 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
324 * Calculate the offset needed to align the type.
325 * size_of_type must be non-zero.
327 static inline lttng_ust_notrace
328 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
);
330 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
338 * lib_ring_buffer_align_ctx - Align context offset on "alignment"
339 * @ctx: ring buffer context.
341 static inline lttng_ust_notrace
342 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
345 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
348 ctx
->buf_offset
+= lib_ring_buffer_align(ctx
->buf_offset
,
353 * lib_ring_buffer_check_config() returns 0 on success.
354 * Used internally to check for valid configurations at channel creation.
356 static inline lttng_ust_notrace
357 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config
*config
,
358 unsigned int switch_timer_interval
,
359 unsigned int read_timer_interval
);
361 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config
*config
,
362 unsigned int switch_timer_interval
,
363 unsigned int read_timer_interval
)
365 if (config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
366 && config
->sync
== RING_BUFFER_SYNC_PER_CPU
367 && switch_timer_interval
)
372 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */