include/lttng/ringbuffer-config.h

   1 #ifndef _LTTNG_RING_BUFFER_CONFIG_H
   2 #define _LTTNG_RING_BUFFER_CONFIG_H
   3
   4 /*
   5  * lttng/ringbuffer-config.h
   6  *
   7  * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Ring buffer configuration header. Note: after declaring the standard inline
  10  * functions, clients should also include linux/ringbuffer/api.h.
  11  *
  12  * Permission is hereby granted, free of charge, to any person obtaining a copy
  13  * of this software and associated documentation files (the "Software"), to deal
  14  * in the Software without restriction, including without limitation the rights
  15  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  16  * copies of the Software, and to permit persons to whom the Software is
  17  * furnished to do so, subject to the following conditions:
  18  *
  19  * The above copyright notice and this permission notice shall be included in
  20  * all copies or substantial portions of the Software.
  21  */
  22
  23 #include <errno.h>
  24 #include "lttng/ust-tracer.h"
  25 #include <stdint.h>
  26 #include <stddef.h>
  27 #include <urcu/arch.h>
  28 #include <string.h>
  29 #include "lttng/align.h"
  30
  31 struct lttng_ust_lib_ring_buffer;
  32 struct channel;
  33 struct lttng_ust_lib_ring_buffer_config;
  34 struct lttng_ust_lib_ring_buffer_ctx;
  35 struct lttng_ust_shm_handle;
  36
  37 /*
  38  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  39  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  40  * provided as inline functions too.  These may simply return 0 if not used by
  41  * the client.
  42  */
  43 struct lttng_ust_lib_ring_buffer_client_cb {
  44         /* Mandatory callbacks */
  45
  46         /* A static inline version is also required for fast path */
  47         uint64_t (*ring_buffer_clock_read) (struct channel *chan);
  48         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  49                                       struct channel *chan, size_t offset,
  50                                       size_t *pre_header_padding,
  51                                       struct lttng_ust_lib_ring_buffer_ctx *ctx);
  52
  53         /* Slow path only, at subbuffer switch */
  54         size_t (*subbuffer_header_size) (void);
  55         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  56                               unsigned int subbuf_idx,
  57                               struct lttng_ust_shm_handle *handle);
  58         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  59                             unsigned int subbuf_idx, unsigned long data_size,
  60                             struct lttng_ust_shm_handle *handle);
  61
  62         /* Optional callbacks (can be set to NULL) */
  63
  64         /* Called at buffer creation/finalize */
  65         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  66                               int cpu, const char *name,
  67                               struct lttng_ust_shm_handle *handle);
  68         /*
  69          * Clients should guarantee that no new reader handle can be opened
  70          * after finalize.
  71          */
  72         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  73                                  void *priv, int cpu,
  74                                  struct lttng_ust_shm_handle *handle);
  75
  76         /*
  77          * Extract header length, payload length and timestamp from event
  78          * record. Used by buffer iterators. Timestamp is only used by channel
  79          * iterator.
  80          */
  81         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  82                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  83                             size_t offset, size_t *header_len,
  84                             size_t *payload_len, uint64_t *timestamp,
  85                             struct lttng_ust_shm_handle *handle);
  86 };
  87
  88 /*
  89  * Ring buffer instance configuration.
  90  *
  91  * Declare as "static const" within the client object to ensure the inline fast
  92  * paths can be optimized.
  93  *
  94  * alloc/sync pairs:
  95  *
  96  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  97  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  98  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  99  *   lib_ring_buffer_put_cpu()).
 100  *
 101  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
 102  *   Per-cpu buffer with global synchronization. Tracing can be performed with
 103  *   preemption enabled, statistically stays on the local buffers.
 104  *
 105  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 106  *   Should only be used for buffers belonging to a single thread or protected
 107  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 108  *   should be disabled in this kind of configuration.
 109  *
 110  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 111  *   Global shared buffer with global synchronization.
 112  *
 113  * wakeup:
 114  *
 115  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 116  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 117  * don't want to call into the wakeup code on the tracing path. Use in
 118  * combination with "read_timer_interval" channel_create() argument.
 119  *
 120  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 121  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 122  * for drivers.
 123  *
 124  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 125  * has the responsibility to perform wakeups.
 126  */
 127 #define LTTNG_UST_RING_BUFFER_CONFIG_PADDING    32
 128 struct lttng_ust_lib_ring_buffer_config {
 129         enum {
 130                 RING_BUFFER_ALLOC_PER_CPU,
 131                 RING_BUFFER_ALLOC_GLOBAL,
 132         } alloc;
 133         enum {
 134                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 135                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 136         } sync;
 137         enum {
 138                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 139                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 140         } mode;
 141         enum {
 142                 RING_BUFFER_SPLICE,
 143                 RING_BUFFER_MMAP,
 144                 RING_BUFFER_READ,               /* TODO */
 145                 RING_BUFFER_ITERATOR,
 146                 RING_BUFFER_NONE,
 147         } output;
 148         enum {
 149                 RING_BUFFER_PAGE,
 150                 RING_BUFFER_VMAP,               /* TODO */
 151                 RING_BUFFER_STATIC,             /* TODO */
 152         } backend;
 153         enum {
 154                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 155                 RING_BUFFER_OOPS_CONSISTENCY,
 156         } oops;
 157         enum {
 158                 RING_BUFFER_IPI_BARRIER,
 159                 RING_BUFFER_NO_IPI_BARRIER,
 160         } ipi;
 161         enum {
 162                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 163                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 164                                                  * writer wakes up reader,
 165                                                  * not lock-free
 166                                                  * (takes spinlock).
 167                                                  */
 168         } wakeup;
 169         /*
 170          * tsc_bits: timestamp bits saved at each record.
 171          *   0 and 64 disable the timestamp compression scheme.
 172          */
 173         unsigned int tsc_bits;
 174         struct lttng_ust_lib_ring_buffer_client_cb cb;
 175         /*
 176          * client_type is used by the consumer process (which is in a
 177          * different address space) to lookup the appropriate client
 178          * callbacks and update the cb pointers.
 179          */
 180         int client_type;
 181         char padding[LTTNG_UST_RING_BUFFER_CONFIG_PADDING];
 182 };
 183
 184 /*
 185  * ring buffer context
 186  *
 187  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 188  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 189  * lib_ring_buffer_write().
 190  */
 191 #define LTTNG_UST_RING_BUFFER_CTX_PADDING       24
 192 struct lttng_ust_lib_ring_buffer_ctx {
 193         /* input received by lib_ring_buffer_reserve(), saved here. */
 194         struct channel *chan;           /* channel */
 195         void *priv;                     /* client private data */
 196         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 197         size_t data_size;               /* size of payload */
 198         int largest_align;              /*
 199                                          * alignment of the largest element
 200                                          * in the payload
 201                                          */
 202         int cpu;                        /* processor id */
 203
 204         /* output from lib_ring_buffer_reserve() */
 205         struct lttng_ust_lib_ring_buffer *buf;  /*
 206                                          * buffer corresponding to processor id
 207                                          * for this channel
 208                                          */
 209         size_t slot_size;               /* size of the reserved slot */
 210         unsigned long buf_offset;       /* offset following the record header */
 211         unsigned long pre_offset;       /*
 212                                          * Initial offset position _before_
 213                                          * the record is written. Positioned
 214                                          * prior to record header alignment
 215                                          * padding.
 216                                          */
 217         uint64_t tsc;                   /* time-stamp counter value */
 218         unsigned int rflags;            /* reservation flags */
 219         char padding[LTTNG_UST_RING_BUFFER_CTX_PADDING];
 220 };
 221
 222 /**
 223  * lib_ring_buffer_ctx_init - initialize ring buffer context
 224  * @ctx: ring buffer context to initialize
 225  * @chan: channel
 226  * @priv: client private data
 227  * @data_size: size of record data payload
 228  * @largest_align: largest alignment within data payload types
 229  * @cpu: processor id
 230  */
 231 static inline
 232 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 233                               struct channel *chan, void *priv,
 234                               size_t data_size, int largest_align,
 235                               int cpu, struct lttng_ust_shm_handle *handle)
 236 {
 237         ctx->chan = chan;
 238         ctx->priv = priv;
 239         ctx->data_size = data_size;
 240         ctx->largest_align = largest_align;
 241         ctx->cpu = cpu;
 242         ctx->rflags = 0;
 243         ctx->handle = handle;
 244         memset(ctx->padding, 0, LTTNG_UST_RING_BUFFER_CTX_PADDING);
 245 }
 246
 247 /*
 248  * Reservation flags.
 249  *
 250  * RING_BUFFER_RFLAG_FULL_TSC
 251  *
 252  * This flag is passed to record_header_size() and to the primitive used to
 253  * write the record header. It indicates that the full 64-bit time value is
 254  * needed in the record header. If this flag is not set, the record header needs
 255  * only to contain "tsc_bits" bit of time value.
 256  *
 257  * Reservation flags can be added by the client, starting from
 258  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 259  * record_header_size() to lib_ring_buffer_write_record_header().
 260  */
 261 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 262 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 263
 264 /*
 265  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 266  * compile-time. We have to duplicate the "config->align" information and the
 267  * definition here because config->align is used both in the slow and fast
 268  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 269  */
 270 #ifdef RING_BUFFER_ALIGN
 271
 272 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 273
 274 /*
 275  * Calculate the offset needed to align the type.
 276  * size_of_type must be non-zero.
 277  */
 278 static inline
 279 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 280 {
 281         return offset_align(align_drift, size_of_type);
 282 }
 283
 284 #else
 285
 286 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 287
 288 /*
 289  * Calculate the offset needed to align the type.
 290  * size_of_type must be non-zero.
 291  */
 292 static inline
 293 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 294 {
 295         return 0;
 296 }
 297
 298 #endif
 299
 300 /**
 301  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 302  * @ctx: ring buffer context.
 303  */
 304 static inline
 305 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 306                            size_t alignment)
 307 {
 308         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 309                                                  alignment);
 310 }
 311
 312 /*
 313  * lib_ring_buffer_check_config() returns 0 on success.
 314  * Used internally to check for valid configurations at channel creation.
 315  */
 316 static inline
 317 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 318                              unsigned int switch_timer_interval,
 319                              unsigned int read_timer_interval)
 320 {
 321         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 322             && config->sync == RING_BUFFER_SYNC_PER_CPU
 323             && switch_timer_interval)
 324                 return -EINVAL;
 325         return 0;
 326 }
 327
 328 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */