2 * SPDX-License-Identifier: MIT
4 * Copyright (C) 2010-2021 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
16 #include <urcu/arch.h>
19 #include <lttng/ust-utils.h>
20 #include <lttng/ust-compiler.h>
21 #include <lttng/ust-tracer.h>
23 struct lttng_ust_ring_buffer
;
24 struct lttng_ust_ring_buffer_channel
;
25 struct lttng_ust_ring_buffer_config
;
26 struct lttng_ust_ring_buffer_ctx_private
;
27 struct lttng_ust_shm_handle
;
30 * Ring buffer client callbacks. Only used by slow path, never on fast path.
31 * For the fast path, record_header_size(), ring_buffer_clock_read() should be
32 * provided as inline functions too. These may simply return 0 if not used by
35 struct lttng_ust_ring_buffer_client_cb
{
36 /* Mandatory callbacks */
38 /* A static inline version is also required for fast path */
39 uint64_t (*ring_buffer_clock_read
) (struct lttng_ust_ring_buffer_channel
*chan
);
40 size_t (*record_header_size
) (const struct lttng_ust_ring_buffer_config
*config
,
41 struct lttng_ust_ring_buffer_channel
*chan
,
43 size_t *pre_header_padding
,
44 struct lttng_ust_ring_buffer_ctx
*ctx
,
47 /* Slow path only, at subbuffer switch */
48 size_t (*subbuffer_header_size
) (void);
49 void (*buffer_begin
) (struct lttng_ust_ring_buffer
*buf
, uint64_t timestamp
,
50 unsigned int subbuf_idx
,
51 struct lttng_ust_shm_handle
*handle
);
52 void (*buffer_end
) (struct lttng_ust_ring_buffer
*buf
, uint64_t timestamp
,
53 unsigned int subbuf_idx
, unsigned long data_size
,
54 struct lttng_ust_shm_handle
*handle
,
55 const struct lttng_ust_ring_buffer_ctx
*ctx
);
57 /* Optional callbacks (can be set to NULL) */
59 /* Called at buffer creation/finalize */
60 int (*buffer_create
) (struct lttng_ust_ring_buffer
*buf
, void *priv
,
61 int cpu
, const char *name
,
62 struct lttng_ust_shm_handle
*handle
);
64 * Clients should guarantee that no new reader handle can be opened
67 void (*buffer_finalize
) (struct lttng_ust_ring_buffer
*buf
,
69 struct lttng_ust_shm_handle
*handle
);
72 * Extract header length, payload length and timestamp from event
73 * record. Used by buffer iterators. Timestamp is only used by channel
76 void (*record_get
) (const struct lttng_ust_ring_buffer_config
*config
,
77 struct lttng_ust_ring_buffer_channel
*chan
,
78 struct lttng_ust_ring_buffer
*buf
,
79 size_t offset
, size_t *header_len
,
80 size_t *payload_len
, uint64_t *timestamp
,
81 struct lttng_ust_shm_handle
*handle
);
83 * Offset and size of content size field in client.
85 void (*content_size_field
) (const struct lttng_ust_ring_buffer_config
*config
,
86 size_t *offset
, size_t *length
);
87 void (*packet_size_field
) (const struct lttng_ust_ring_buffer_config
*config
,
88 size_t *offset
, size_t *length
);
92 * Ring buffer instance configuration.
94 * Declare as "static const" within the client object to ensure the inline fast
95 * paths can be optimized.
99 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
100 * Per-cpu buffers with per-cpu synchronization.
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_ring_buffer_alloc_types
{
131 RING_BUFFER_ALLOC_PER_CPU
,
132 RING_BUFFER_ALLOC_GLOBAL
,
135 enum lttng_ust_ring_buffer_sync_types
{
136 RING_BUFFER_SYNC_PER_CPU
, /* Wait-free */
137 RING_BUFFER_SYNC_GLOBAL
, /* Lock-free */
140 enum lttng_ust_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_ring_buffer_output_types
{
148 RING_BUFFER_READ
, /* TODO */
149 RING_BUFFER_ITERATOR
,
153 enum lttng_ust_ring_buffer_backend_types
{
155 RING_BUFFER_VMAP
, /* TODO */
156 RING_BUFFER_STATIC
, /* TODO */
159 enum lttng_ust_ring_buffer_oops_types
{
160 RING_BUFFER_NO_OOPS_CONSISTENCY
,
161 RING_BUFFER_OOPS_CONSISTENCY
,
164 enum lttng_ust_ring_buffer_ipi_types
{
165 RING_BUFFER_IPI_BARRIER
,
166 RING_BUFFER_NO_IPI_BARRIER
,
169 enum lttng_ust_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_ring_buffer_config
{
179 enum lttng_ust_ring_buffer_alloc_types alloc
;
180 enum lttng_ust_ring_buffer_sync_types sync
;
181 enum lttng_ust_ring_buffer_mode_types mode
;
182 enum lttng_ust_ring_buffer_output_types output
;
183 enum lttng_ust_ring_buffer_backend_types backend
;
184 enum lttng_ust_ring_buffer_oops_types oops
;
185 enum lttng_ust_ring_buffer_ipi_types ipi
;
186 enum lttng_ust_ring_buffer_wakeup_types wakeup
;
188 * timestamp_bits: timestamp bits saved at each record.
189 * 0 and 64 disable the timestamp compression scheme.
191 unsigned int timestamp_bits
;
192 struct lttng_ust_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_ring_buffer_client_cb
*cb_ptr
;
201 char padding
[LTTNG_UST_RING_BUFFER_CONFIG_PADDING
];
207 * RING_BUFFER_RFLAG_FULL_TIMESTAMP
209 * This flag is passed to record_header_size() and to the primitive used to
210 * write the record header. It indicates that the full 64-bit time value is
211 * needed in the record header. If this flag is not set, the record header needs
212 * only to contain "timestamp_bits" bit of time value.
214 * Reservation flags can be added by the client, starting from
215 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
216 * record_header_size() to lib_ring_buffer_write_record_header().
218 #define RING_BUFFER_RFLAG_FULL_TIMESTAMP (1U << 0)
219 #define RING_BUFFER_RFLAG_END (1U << 1)
222 * lib_ring_buffer_check_config() returns 0 on success.
223 * Used internally to check for valid configurations at channel creation.
226 int lib_ring_buffer_check_config(const struct lttng_ust_ring_buffer_config
*config
,
227 unsigned int switch_timer_interval
,
228 unsigned int read_timer_interval
)
232 int lib_ring_buffer_check_config(const struct lttng_ust_ring_buffer_config
*config
,
233 unsigned int switch_timer_interval
,
234 unsigned int read_timer_interval
__attribute__((unused
)))
236 if (config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
237 && config
->sync
== RING_BUFFER_SYNC_PER_CPU
238 && switch_timer_interval
)
243 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */