1 #ifndef _LINUX_RING_BUFFER_CONFIG_H
2 #define _LINUX_RING_BUFFER_CONFIG_H
5 * linux/ringbuffer/config.h
7 * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
9 * Ring buffer configuration header. Note: after declaring the standard inline
10 * functions, clients should also include linux/ringbuffer/api.h.
12 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
13 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
15 * Permission is hereby granted to use or copy this program
16 * for any purpose, provided the above notices are retained on all copies.
17 * Permission to modify the code and to distribute modified code is granted,
18 * provided the above notices are retained, and a notice that the code was
19 * modified is included with the above copyright notice.
23 #include "lttng/ust-tracer.h"
26 #include <urcu/arch.h>
27 #include "lttng/align.h"
29 struct lttng_ust_lib_ring_buffer
;
31 struct lttng_ust_lib_ring_buffer_config
;
32 struct lttng_ust_lib_ring_buffer_ctx
;
33 struct lttng_ust_shm_handle
*handle
;
36 * Ring buffer client callbacks. Only used by slow path, never on fast path.
37 * For the fast path, record_header_size(), ring_buffer_clock_read() should be
38 * provided as inline functions too. These may simply return 0 if not used by
41 struct lttng_ust_lib_ring_buffer_client_cb
{
42 /* Mandatory callbacks */
44 /* A static inline version is also required for fast path */
45 uint64_t (*ring_buffer_clock_read
) (struct channel
*chan
);
46 size_t (*record_header_size
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
47 struct channel
*chan
, size_t offset
,
48 size_t *pre_header_padding
,
49 struct lttng_ust_lib_ring_buffer_ctx
*ctx
);
51 /* Slow path only, at subbuffer switch */
52 size_t (*subbuffer_header_size
) (void);
53 void (*buffer_begin
) (struct lttng_ust_lib_ring_buffer
*buf
, uint64_t tsc
,
54 unsigned int subbuf_idx
,
55 struct lttng_ust_shm_handle
*handle
);
56 void (*buffer_end
) (struct lttng_ust_lib_ring_buffer
*buf
, uint64_t tsc
,
57 unsigned int subbuf_idx
, unsigned long data_size
,
58 struct lttng_ust_shm_handle
*handle
);
60 /* Optional callbacks (can be set to NULL) */
62 /* Called at buffer creation/finalize */
63 int (*buffer_create
) (struct lttng_ust_lib_ring_buffer
*buf
, void *priv
,
64 int cpu
, const char *name
,
65 struct lttng_ust_shm_handle
*handle
);
67 * Clients should guarantee that no new reader handle can be opened
70 void (*buffer_finalize
) (struct lttng_ust_lib_ring_buffer
*buf
,
72 struct lttng_ust_shm_handle
*handle
);
75 * Extract header length, payload length and timestamp from event
76 * record. Used by buffer iterators. Timestamp is only used by channel
79 void (*record_get
) (const struct lttng_ust_lib_ring_buffer_config
*config
,
80 struct channel
*chan
, struct lttng_ust_lib_ring_buffer
*buf
,
81 size_t offset
, size_t *header_len
,
82 size_t *payload_len
, uint64_t *timestamp
,
83 struct lttng_ust_shm_handle
*handle
);
87 * Ring buffer instance configuration.
89 * Declare as "static const" within the client object to ensure the inline fast
90 * paths can be optimized.
94 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
95 * Per-cpu buffers with per-cpu synchronization. Tracing must be performed
96 * with preemption disabled (lib_ring_buffer_get_cpu() and
97 * lib_ring_buffer_put_cpu()).
99 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
100 * Per-cpu buffer with global synchronization. Tracing can be performed with
101 * preemption enabled, statistically stays on the local buffers.
103 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
104 * Should only be used for buffers belonging to a single thread or protected
105 * by mutual exclusion by the client. Note that periodical sub-buffer switch
106 * should be disabled in this kind of configuration.
108 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
109 * Global shared buffer with global synchronization.
113 * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
114 * buffers and wake up readers if data is ready. Mainly useful for tracers which
115 * don't want to call into the wakeup code on the tracing path. Use in
116 * combination with "read_timer_interval" channel_create() argument.
118 * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
119 * ready to read. Lower latencies before the reader is woken up. Mainly suitable
122 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
123 * has the responsibility to perform wakeups.
125 struct lttng_ust_lib_ring_buffer_config
{
127 RING_BUFFER_ALLOC_PER_CPU
,
128 RING_BUFFER_ALLOC_GLOBAL
,
131 RING_BUFFER_SYNC_PER_CPU
, /* Wait-free */
132 RING_BUFFER_SYNC_GLOBAL
, /* Lock-free */
135 RING_BUFFER_OVERWRITE
, /* Overwrite when buffer full */
136 RING_BUFFER_DISCARD
, /* Discard when buffer full */
141 RING_BUFFER_READ
, /* TODO */
142 RING_BUFFER_ITERATOR
,
147 RING_BUFFER_VMAP
, /* TODO */
148 RING_BUFFER_STATIC
, /* TODO */
151 RING_BUFFER_NO_OOPS_CONSISTENCY
,
152 RING_BUFFER_OOPS_CONSISTENCY
,
155 RING_BUFFER_IPI_BARRIER
,
156 RING_BUFFER_NO_IPI_BARRIER
,
159 RING_BUFFER_WAKEUP_BY_TIMER
, /* wake up performed by timer */
160 RING_BUFFER_WAKEUP_BY_WRITER
, /*
161 * writer wakes up reader,
167 * tsc_bits: timestamp bits saved at each record.
168 * 0 and 64 disable the timestamp compression scheme.
170 unsigned int tsc_bits
;
171 struct lttng_ust_lib_ring_buffer_client_cb cb
;
173 * client_type is used by the consumer process (which is in a
174 * different address space) to lookup the appropriate client
175 * callbacks and update the cb pointers.
181 * ring buffer context
183 * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
184 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
185 * lib_ring_buffer_write().
187 struct lttng_ust_lib_ring_buffer_ctx
{
188 /* input received by lib_ring_buffer_reserve(), saved here. */
189 struct channel
*chan
; /* channel */
190 void *priv
; /* client private data */
191 struct lttng_ust_shm_handle
*handle
; /* shared-memory handle */
192 size_t data_size
; /* size of payload */
193 int largest_align
; /*
194 * alignment of the largest element
197 int cpu
; /* processor id */
199 /* output from lib_ring_buffer_reserve() */
200 struct lttng_ust_lib_ring_buffer
*buf
; /*
201 * buffer corresponding to processor id
204 size_t slot_size
; /* size of the reserved slot */
205 unsigned long buf_offset
; /* offset following the record header */
206 unsigned long pre_offset
; /*
207 * Initial offset position _before_
208 * the record is written. Positioned
209 * prior to record header alignment
212 uint64_t tsc
; /* time-stamp counter value */
213 unsigned int rflags
; /* reservation flags */
217 * lib_ring_buffer_ctx_init - initialize ring buffer context
218 * @ctx: ring buffer context to initialize
220 * @priv: client private data
221 * @data_size: size of record data payload
222 * @largest_align: largest alignment within data payload types
226 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
227 struct channel
*chan
, void *priv
,
228 size_t data_size
, int largest_align
,
229 int cpu
, struct lttng_ust_shm_handle
*handle
)
233 ctx
->data_size
= data_size
;
234 ctx
->largest_align
= largest_align
;
237 ctx
->handle
= handle
;
243 * RING_BUFFER_RFLAG_FULL_TSC
245 * This flag is passed to record_header_size() and to the primitive used to
246 * write the record header. It indicates that the full 64-bit time value is
247 * needed in the record header. If this flag is not set, the record header needs
248 * only to contain "tsc_bits" bit of time value.
250 * Reservation flags can be added by the client, starting from
251 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
252 * record_header_size() to lib_ring_buffer_write_record_header().
254 #define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
255 #define RING_BUFFER_RFLAG_END (1U << 1)
258 * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
259 * compile-time. We have to duplicate the "config->align" information and the
260 * definition here because config->align is used both in the slow and fast
261 * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
263 #ifdef RING_BUFFER_ALIGN
265 # define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
268 * Calculate the offset needed to align the type.
269 * size_of_type must be non-zero.
272 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
274 return offset_align(align_drift
, size_of_type
);
279 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
282 * Calculate the offset needed to align the type.
283 * size_of_type must be non-zero.
286 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
294 * lib_ring_buffer_align_ctx - Align context offset on "alignment"
295 * @ctx: ring buffer context.
298 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx
*ctx
,
301 ctx
->buf_offset
+= lib_ring_buffer_align(ctx
->buf_offset
,
306 * lib_ring_buffer_check_config() returns 0 on success.
307 * Used internally to check for valid configurations at channel creation.
310 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config
*config
,
311 unsigned int switch_timer_interval
,
312 unsigned int read_timer_interval
)
314 if (config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
315 && config
->sync
== RING_BUFFER_SYNC_PER_CPU
316 && switch_timer_interval
)
321 #endif /* _LINUX_RING_BUFFER_CONFIG_H */