1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
5 * Ring buffer configuration header. Note: after declaring the standard inline
6 * functions, clients should also include linux/ringbuffer/api.h.
8 * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
11 #ifndef _LIB_RING_BUFFER_CONFIG_H
12 #define _LIB_RING_BUFFER_CONFIG_H
14 #include <linux/types.h>
15 #include <linux/percpu.h>
16 #include <lttng/align.h>
17 #include <lttng/tracer-core.h>
19 struct lib_ring_buffer
;
21 struct lib_ring_buffer_config
;
22 struct lib_ring_buffer_ctx
;
25 * Ring buffer client callbacks. Only used by slow path, never on fast path.
26 * For the fast path, record_header_size(), ring_buffer_clock_read() should be
27 * provided as inline functions too. These may simply return 0 if not used by
30 struct lib_ring_buffer_client_cb
{
31 /* Mandatory callbacks */
33 /* A static inline version is also required for fast path */
34 u64 (*ring_buffer_clock_read
) (struct channel
*chan
);
35 size_t (*record_header_size
) (const struct lib_ring_buffer_config
*config
,
36 struct channel
*chan
, size_t offset
,
37 size_t *pre_header_padding
,
38 struct lib_ring_buffer_ctx
*ctx
,
41 /* Slow path only, at subbuffer switch */
42 size_t (*subbuffer_header_size
) (void);
43 void (*buffer_begin
) (struct lib_ring_buffer
*buf
, u64 tsc
,
44 unsigned int subbuf_idx
);
45 void (*buffer_end
) (struct lib_ring_buffer
*buf
, u64 tsc
,
46 unsigned int subbuf_idx
, unsigned long data_size
);
48 /* Optional callbacks (can be set to NULL) */
50 /* Called at buffer creation/finalize */
51 int (*buffer_create
) (struct lib_ring_buffer
*buf
, void *priv
,
52 int cpu
, const char *name
);
54 * Clients should guarantee that no new reader handle can be opened
57 void (*buffer_finalize
) (struct lib_ring_buffer
*buf
, void *priv
, int cpu
);
60 * Extract header length, payload length and timestamp from event
61 * record. Used by buffer iterators. Timestamp is only used by channel
64 void (*record_get
) (const struct lib_ring_buffer_config
*config
,
65 struct channel
*chan
, struct lib_ring_buffer
*buf
,
66 size_t offset
, size_t *header_len
,
67 size_t *payload_len
, u64
*timestamp
);
71 * Ring buffer instance configuration.
73 * Declare as "static const" within the client object to ensure the inline fast
74 * paths can be optimized.
78 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
79 * Per-cpu buffers with per-cpu synchronization. Tracing must be performed
80 * with preemption disabled (lib_ring_buffer_get_cpu() and
81 * lib_ring_buffer_put_cpu()).
83 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
84 * Per-cpu buffer with global synchronization. Tracing can be performed with
85 * preemption enabled, statistically stays on the local buffers.
87 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
88 * Should only be used for buffers belonging to a single thread or protected
89 * by mutual exclusion by the client. Note that periodical sub-buffer switch
90 * should be disabled in this kind of configuration.
92 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
93 * Global shared buffer with global synchronization.
97 * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
98 * buffers and wake up readers if data is ready. Mainly useful for tracers which
99 * don't want to call into the wakeup code on the tracing path. Use in
100 * combination with "read_timer_interval" channel_create() argument.
102 * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
103 * ready to read. Lower latencies before the reader is woken up. Mainly suitable
104 * for drivers. Going through an "irq_work" allows triggering this type of wakeup
105 * even from NMI context: the wakeup will be slightly delayed until the next
106 * interrupts are handled.
108 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
109 * has the responsibility to perform wakeups.
111 struct lib_ring_buffer_config
{
113 RING_BUFFER_ALLOC_PER_CPU
,
114 RING_BUFFER_ALLOC_GLOBAL
,
117 RING_BUFFER_SYNC_PER_CPU
, /* Wait-free */
118 RING_BUFFER_SYNC_GLOBAL
, /* Lock-free */
121 RING_BUFFER_OVERWRITE
, /* Overwrite when buffer full */
122 RING_BUFFER_DISCARD
, /* Discard when buffer full */
127 RING_BUFFER_READ
, /* TODO */
128 RING_BUFFER_ITERATOR
,
133 RING_BUFFER_VMAP
, /* TODO */
134 RING_BUFFER_STATIC
, /* TODO */
137 RING_BUFFER_NO_OOPS_CONSISTENCY
,
138 RING_BUFFER_OOPS_CONSISTENCY
,
141 RING_BUFFER_IPI_BARRIER
,
142 RING_BUFFER_NO_IPI_BARRIER
,
145 RING_BUFFER_WAKEUP_BY_TIMER
, /* wake up performed by timer */
146 RING_BUFFER_WAKEUP_BY_WRITER
, /*
147 * writer wakes up reader through
152 * tsc_bits: timestamp bits saved at each record.
153 * 0 and 64 disable the timestamp compression scheme.
155 unsigned int tsc_bits
;
156 struct lib_ring_buffer_client_cb cb
;
160 * ring buffer context
162 * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
163 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
164 * lib_ring_buffer_write().
166 struct lib_ring_buffer_ctx
{
167 /* input received by lib_ring_buffer_reserve(), saved here. */
168 struct channel
*chan
; /* channel */
169 void *priv
; /* client private data */
170 size_t data_size
; /* size of payload */
171 int largest_align
; /*
172 * alignment of the largest element
175 int cpu
; /* processor id */
177 /* output from lib_ring_buffer_reserve() */
178 struct lib_ring_buffer
*buf
; /*
179 * buffer corresponding to processor id
182 size_t slot_size
; /* size of the reserved slot */
183 unsigned long buf_offset
; /* offset following the record header */
184 unsigned long pre_offset
; /*
185 * Initial offset position _before_
186 * the record is written. Positioned
187 * prior to record header alignment
190 u64 tsc
; /* time-stamp counter value */
191 unsigned int rflags
; /* reservation flags */
192 /* Cache backend pages pointer chasing. */
193 struct lib_ring_buffer_backend_pages
*backend_pages
;
197 * lib_ring_buffer_ctx_init - initialize ring buffer context
198 * @ctx: ring buffer context to initialize
200 * @priv: client private data
201 * @data_size: size of record data payload. It must be greater than 0.
202 * @largest_align: largest alignment within data payload types
206 void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx
*ctx
,
207 struct channel
*chan
,
208 size_t data_size
, int largest_align
,
213 ctx
->data_size
= data_size
;
214 ctx
->largest_align
= largest_align
;
217 ctx
->backend_pages
= NULL
;
223 * RING_BUFFER_RFLAG_FULL_TSC
225 * This flag is passed to record_header_size() and to the primitive used to
226 * write the record header. It indicates that the full 64-bit time value is
227 * needed in the record header. If this flag is not set, the record header needs
228 * only to contain "tsc_bits" bit of time value.
230 * Reservation flags can be added by the client, starting from
231 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
232 * record_header_size() to lib_ring_buffer_write_record_header().
234 #define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
235 #define RING_BUFFER_RFLAG_END (1U << 1)
237 #ifndef LTTNG_TRACER_CORE_H
238 #error "lttng/tracer-core.h is needed for RING_BUFFER_ALIGN define"
242 * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
243 * compile-time. We have to duplicate the "config->align" information and the
244 * definition here because config->align is used both in the slow and fast
245 * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
247 #ifdef RING_BUFFER_ALIGN
249 # define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
252 * Calculate the offset needed to align the type.
253 * size_of_type must be non-zero.
256 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
258 return offset_align(align_drift
, size_of_type
);
263 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
266 * Calculate the offset needed to align the type.
267 * size_of_type must be non-zero.
270 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
278 * lib_ring_buffer_align_ctx - Align context offset on "alignment"
279 * @ctx: ring buffer context.
282 void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx
*ctx
,
285 ctx
->buf_offset
+= lib_ring_buffer_align(ctx
->buf_offset
,
290 * lib_ring_buffer_check_config() returns 0 on success.
291 * Used internally to check for valid configurations at channel creation.
294 int lib_ring_buffer_check_config(const struct lib_ring_buffer_config
*config
,
295 unsigned int switch_timer_interval
,
296 unsigned int read_timer_interval
)
298 if (config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
299 && config
->sync
== RING_BUFFER_SYNC_PER_CPU
300 && switch_timer_interval
)
305 #include <ringbuffer/vatomic.h>
307 #endif /* _LIB_RING_BUFFER_CONFIG_H */