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 * Dual LGPL v2.1/GPL v2 license.
16 #include "ust/kcompat/kcompat.h"
17 #include "ust/align.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
);
40 /* Slow path only, at subbuffer switch */
41 size_t (*subbuffer_header_size
) (void);
42 void (*buffer_begin
) (struct lib_ring_buffer
*buf
, u64 tsc
,
43 unsigned int subbuf_idx
);
44 void (*buffer_end
) (struct lib_ring_buffer
*buf
, u64 tsc
,
45 unsigned int subbuf_idx
, unsigned long data_size
);
47 /* Optional callbacks (can be set to NULL) */
49 /* Called at buffer creation/finalize */
50 int (*buffer_create
) (struct lib_ring_buffer
*buf
, void *priv
,
51 int cpu
, const char *name
);
53 * Clients should guarantee that no new reader handle can be opened
56 void (*buffer_finalize
) (struct lib_ring_buffer
*buf
, void *priv
, int cpu
);
59 * Extract header length, payload length and timestamp from event
60 * record. Used by buffer iterators. Timestamp is only used by channel
63 void (*record_get
) (const struct lib_ring_buffer_config
*config
,
64 struct channel
*chan
, struct lib_ring_buffer
*buf
,
65 size_t offset
, size_t *header_len
,
66 size_t *payload_len
, u64
*timestamp
);
70 * Ring buffer instance configuration.
72 * Declare as "static const" within the client object to ensure the inline fast
73 * paths can be optimized.
77 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
78 * Per-cpu buffers with per-cpu synchronization. Tracing must be performed
79 * with preemption disabled (lib_ring_buffer_get_cpu() and
80 * lib_ring_buffer_put_cpu()).
82 * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
83 * Per-cpu buffer with global synchronization. Tracing can be performed with
84 * preemption enabled, statistically stays on the local buffers.
86 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
87 * Should only be used for buffers belonging to a single thread or protected
88 * by mutual exclusion by the client. Note that periodical sub-buffer switch
89 * should be disabled in this kind of configuration.
91 * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
92 * Global shared buffer with global synchronization.
96 * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
97 * buffers and wake up readers if data is ready. Mainly useful for tracers which
98 * don't want to call into the wakeup code on the tracing path. Use in
99 * combination with "read_timer_interval" channel_create() argument.
101 * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
102 * ready to read. Lower latencies before the reader is woken up. Mainly suitable
105 * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
106 * has the responsibility to perform wakeups.
108 struct lib_ring_buffer_config
{
110 RING_BUFFER_ALLOC_PER_CPU
,
111 RING_BUFFER_ALLOC_GLOBAL
,
114 RING_BUFFER_SYNC_PER_CPU
, /* Wait-free */
115 RING_BUFFER_SYNC_GLOBAL
, /* Lock-free */
118 RING_BUFFER_OVERWRITE
, /* Overwrite when buffer full */
119 RING_BUFFER_DISCARD
, /* Discard when buffer full */
124 RING_BUFFER_READ
, /* TODO */
125 RING_BUFFER_ITERATOR
,
130 RING_BUFFER_VMAP
, /* TODO */
131 RING_BUFFER_STATIC
, /* TODO */
134 RING_BUFFER_NO_OOPS_CONSISTENCY
,
135 RING_BUFFER_OOPS_CONSISTENCY
,
138 RING_BUFFER_IPI_BARRIER
,
139 RING_BUFFER_NO_IPI_BARRIER
,
142 RING_BUFFER_WAKEUP_BY_TIMER
, /* wake up performed by timer */
143 RING_BUFFER_WAKEUP_BY_WRITER
, /*
144 * writer wakes up reader,
150 * tsc_bits: timestamp bits saved at each record.
151 * 0 and 64 disable the timestamp compression scheme.
153 unsigned int tsc_bits
;
154 struct lib_ring_buffer_client_cb cb
;
158 * ring buffer context
160 * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
161 * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
162 * lib_ring_buffer_write().
164 struct lib_ring_buffer_ctx
{
165 /* input received by lib_ring_buffer_reserve(), saved here. */
166 struct channel
*chan
; /* channel */
167 void *priv
; /* client private data */
168 size_t data_size
; /* size of payload */
169 int largest_align
; /*
170 * alignment of the largest element
173 int cpu
; /* processor id */
175 /* output from lib_ring_buffer_reserve() */
176 struct lib_ring_buffer
*buf
; /*
177 * buffer corresponding to processor id
180 size_t slot_size
; /* size of the reserved slot */
181 unsigned long buf_offset
; /* offset following the record header */
182 unsigned long pre_offset
; /*
183 * Initial offset position _before_
184 * the record is written. Positioned
185 * prior to record header alignment
188 u64 tsc
; /* time-stamp counter value */
189 unsigned int rflags
; /* reservation flags */
193 * lib_ring_buffer_ctx_init - initialize ring buffer context
194 * @ctx: ring buffer context to initialize
196 * @priv: client private data
197 * @data_size: size of record data payload
198 * @largest_align: largest alignment within data payload types
202 void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx
*ctx
,
203 struct channel
*chan
, void *priv
,
204 size_t data_size
, int largest_align
,
209 ctx
->data_size
= data_size
;
210 ctx
->largest_align
= largest_align
;
218 * RING_BUFFER_RFLAG_FULL_TSC
220 * This flag is passed to record_header_size() and to the primitive used to
221 * write the record header. It indicates that the full 64-bit time value is
222 * needed in the record header. If this flag is not set, the record header needs
223 * only to contain "tsc_bits" bit of time value.
225 * Reservation flags can be added by the client, starting from
226 * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
227 * record_header_size() to lib_ring_buffer_write_record_header().
229 #define RING_BUFFER_RFLAG_FULL_TSC (1U << 0)
230 #define RING_BUFFER_RFLAG_END (1U << 1)
233 * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
234 * compile-time. We have to duplicate the "config->align" information and the
235 * definition here because config->align is used both in the slow and fast
236 * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
238 #ifdef RING_BUFFER_ALIGN
240 # define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */
243 * Calculate the offset needed to align the type.
244 * size_of_type must be non-zero.
247 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
249 return offset_align(align_drift
, size_of_type
);
254 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
257 * Calculate the offset needed to align the type.
258 * size_of_type must be non-zero.
261 unsigned int lib_ring_buffer_align(size_t align_drift
, size_t size_of_type
)
269 * lib_ring_buffer_align_ctx - Align context offset on "alignment"
270 * @ctx: ring buffer context.
273 void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx
*ctx
,
276 ctx
->buf_offset
+= lib_ring_buffer_align(ctx
->buf_offset
,
281 * lib_ring_buffer_check_config() returns 0 on success.
282 * Used internally to check for valid configurations at channel creation.
285 int lib_ring_buffer_check_config(const struct lib_ring_buffer_config
*config
,
286 unsigned int switch_timer_interval
,
287 unsigned int read_timer_interval
)
289 if (config
->alloc
== RING_BUFFER_ALLOC_GLOBAL
290 && config
->sync
== RING_BUFFER_SYNC_PER_CPU
291 && switch_timer_interval
)
298 #endif /* _LINUX_RING_BUFFER_CONFIG_H */