include/lttng/ringbuffer-config.h

   1 /*
   2  * SPDX-License-Identifier: MIT
   3  *
   4  * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Ring buffer configuration header. Note: after declaring the standard inline
   7  * functions, clients should also include linux/ringbuffer/api.h.
   8  */
   9
  10 #ifndef _LTTNG_RING_BUFFER_CONFIG_H
  11 #define _LTTNG_RING_BUFFER_CONFIG_H
  12
  13 #include <errno.h>
  14 #include "lttng/ust-tracer.h"
  15 #include <stdint.h>
  16 #include <stddef.h>
  17 #include <urcu/arch.h>
  18 #include <string.h>
  19 #include "lttng/align.h"
  20 #include <lttng/ust-compiler.h>
  21
  22 struct lttng_ust_lib_ring_buffer;
  23 struct channel;
  24 struct lttng_ust_lib_ring_buffer_config;
  25 struct lttng_ust_lib_ring_buffer_ctx;
  26 struct lttng_ust_shm_handle;
  27
  28 /*
  29  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  30  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  31  * provided as inline functions too.  These may simply return 0 if not used by
  32  * the client.
  33  */
  34 struct lttng_ust_lib_ring_buffer_client_cb {
  35         /* Mandatory callbacks */
  36
  37         /* A static inline version is also required for fast path */
  38         uint64_t (*ring_buffer_clock_read) (struct channel *chan);
  39         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  40                                       struct channel *chan, size_t offset,
  41                                       size_t *pre_header_padding,
  42                                       struct lttng_ust_lib_ring_buffer_ctx *ctx,
  43                                       void *client_ctx);
  44
  45         /* Slow path only, at subbuffer switch */
  46         size_t (*subbuffer_header_size) (void);
  47         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  48                               unsigned int subbuf_idx,
  49                               struct lttng_ust_shm_handle *handle);
  50         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  51                             unsigned int subbuf_idx, unsigned long data_size,
  52                             struct lttng_ust_shm_handle *handle);
  53
  54         /* Optional callbacks (can be set to NULL) */
  55
  56         /* Called at buffer creation/finalize */
  57         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  58                               int cpu, const char *name,
  59                               struct lttng_ust_shm_handle *handle);
  60         /*
  61          * Clients should guarantee that no new reader handle can be opened
  62          * after finalize.
  63          */
  64         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  65                                  void *priv, int cpu,
  66                                  struct lttng_ust_shm_handle *handle);
  67
  68         /*
  69          * Extract header length, payload length and timestamp from event
  70          * record. Used by buffer iterators. Timestamp is only used by channel
  71          * iterator.
  72          */
  73         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  74                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  75                             size_t offset, size_t *header_len,
  76                             size_t *payload_len, uint64_t *timestamp,
  77                             struct lttng_ust_shm_handle *handle);
  78         /*
  79          * Offset and size of content size field in client.
  80          */
  81         void (*content_size_field) (const struct lttng_ust_lib_ring_buffer_config *config,
  82                                 size_t *offset, size_t *length);
  83         void (*packet_size_field) (const struct lttng_ust_lib_ring_buffer_config *config,
  84                                 size_t *offset, size_t *length);
  85 };
  86
  87 /*
  88  * Ring buffer instance configuration.
  89  *
  90  * Declare as "static const" within the client object to ensure the inline fast
  91  * paths can be optimized.
  92  *
  93  * alloc/sync pairs:
  94  *
  95  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  96  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  97  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  98  *   lib_ring_buffer_put_cpu()).
  99  *
 100  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
 101  *   Per-cpu buffer with global synchronization. Tracing can be performed with
 102  *   preemption enabled, statistically stays on the local buffers.
 103  *
 104  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 105  *   Should only be used for buffers belonging to a single thread or protected
 106  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 107  *   should be disabled in this kind of configuration.
 108  *
 109  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 110  *   Global shared buffer with global synchronization.
 111  *
 112  * wakeup:
 113  *
 114  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 115  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 116  * don't want to call into the wakeup code on the tracing path. Use in
 117  * combination with "read_timer_interval" channel_create() argument.
 118  *
 119  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 120  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 121  * for drivers.
 122  *
 123  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 124  * has the responsibility to perform wakeups.
 125  */
 126 #define LTTNG_UST_RING_BUFFER_CONFIG_PADDING    20
 127
 128 enum lttng_ust_lib_ring_buffer_alloc_types {
 129         RING_BUFFER_ALLOC_PER_CPU,
 130         RING_BUFFER_ALLOC_GLOBAL,
 131 };
 132
 133 enum lttng_ust_lib_ring_buffer_sync_types {
 134         RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 135         RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 136 };
 137
 138 enum lttng_ust_lib_ring_buffer_mode_types {
 139         RING_BUFFER_OVERWRITE = 0,      /* Overwrite when buffer full */
 140         RING_BUFFER_DISCARD = 1,        /* Discard when buffer full */
 141 };
 142
 143 enum lttng_ust_lib_ring_buffer_output_types {
 144         RING_BUFFER_SPLICE,
 145         RING_BUFFER_MMAP,
 146         RING_BUFFER_READ,               /* TODO */
 147         RING_BUFFER_ITERATOR,
 148         RING_BUFFER_NONE,
 149 };
 150
 151 enum lttng_ust_lib_ring_buffer_backend_types {
 152         RING_BUFFER_PAGE,
 153         RING_BUFFER_VMAP,               /* TODO */
 154         RING_BUFFER_STATIC,             /* TODO */
 155 };
 156
 157 enum lttng_ust_lib_ring_buffer_oops_types {
 158         RING_BUFFER_NO_OOPS_CONSISTENCY,
 159         RING_BUFFER_OOPS_CONSISTENCY,
 160 };
 161
 162 enum lttng_ust_lib_ring_buffer_ipi_types {
 163         RING_BUFFER_IPI_BARRIER,
 164         RING_BUFFER_NO_IPI_BARRIER,
 165 };
 166
 167 enum lttng_ust_lib_ring_buffer_wakeup_types {
 168         RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 169         RING_BUFFER_WAKEUP_BY_WRITER,   /*
 170                                          * writer wakes up reader,
 171                                          * not lock-free
 172                                          * (takes spinlock).
 173                                          */
 174 };
 175
 176 struct lttng_ust_lib_ring_buffer_config {
 177         enum lttng_ust_lib_ring_buffer_alloc_types alloc;
 178         enum lttng_ust_lib_ring_buffer_sync_types sync;
 179         enum lttng_ust_lib_ring_buffer_mode_types mode;
 180         enum lttng_ust_lib_ring_buffer_output_types output;
 181         enum lttng_ust_lib_ring_buffer_backend_types backend;
 182         enum lttng_ust_lib_ring_buffer_oops_types oops;
 183         enum lttng_ust_lib_ring_buffer_ipi_types ipi;
 184         enum lttng_ust_lib_ring_buffer_wakeup_types wakeup;
 185         /*
 186          * tsc_bits: timestamp bits saved at each record.
 187          *   0 and 64 disable the timestamp compression scheme.
 188          */
 189         unsigned int tsc_bits;
 190         struct lttng_ust_lib_ring_buffer_client_cb cb;
 191         /*
 192          * client_type is used by the consumer process (which is in a
 193          * different address space) to lookup the appropriate client
 194          * callbacks and update the cb pointers.
 195          */
 196         int client_type;
 197         int _unused1;
 198         const struct lttng_ust_lib_ring_buffer_client_cb *cb_ptr;
 199         char padding[LTTNG_UST_RING_BUFFER_CONFIG_PADDING];
 200 };
 201
 202 /*
 203  * ring buffer context
 204  *
 205  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 206  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 207  * lib_ring_buffer_write().
 208  *
 209  * IMPORTANT: this structure is part of the ABI between the probe and
 210  * UST. Fields need to be only added at the end, never reordered, never
 211  * removed.
 212  */
 213 #define LTTNG_UST_RING_BUFFER_CTX_PADDING       \
 214                 (24 - sizeof(int) - sizeof(void *) - sizeof(void *))
 215 struct lttng_ust_lib_ring_buffer_ctx {
 216         /* input received by lib_ring_buffer_reserve(), saved here. */
 217         struct channel *chan;           /* channel */
 218         void *priv;                     /* client private data */
 219         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 220         size_t data_size;               /* size of payload */
 221         int largest_align;              /*
 222                                          * alignment of the largest element
 223                                          * in the payload
 224                                          */
 225         int cpu;                        /* processor id */
 226
 227         /* output from lib_ring_buffer_reserve() */
 228         struct lttng_ust_lib_ring_buffer *buf;  /*
 229                                          * buffer corresponding to processor id
 230                                          * for this channel
 231                                          */
 232         size_t slot_size;               /* size of the reserved slot */
 233         unsigned long buf_offset;       /* offset following the record header */
 234         unsigned long pre_offset;       /*
 235                                          * Initial offset position _before_
 236                                          * the record is written. Positioned
 237                                          * prior to record header alignment
 238                                          * padding.
 239                                          */
 240         uint64_t tsc;                   /* time-stamp counter value */
 241         unsigned int rflags;            /* reservation flags */
 242         /*
 243          * The field ctx_len is the length of struct
 244          * lttng_ust_lib_ring_buffer_ctx as known by the user of
 245          * lib_ring_buffer_ctx_init.
 246          */
 247         unsigned int ctx_len;
 248         void *ip;                       /* caller ip address */
 249         void *priv2;                    /* 2nd priv data */
 250         char padding2[LTTNG_UST_RING_BUFFER_CTX_PADDING];
 251         /*
 252          * This is the end of the initial fields expected by the original ABI
 253          * between probes and UST. Only the fields above can be used if
 254          * ctx_len is 0. Use the value of ctx_len to find out which of the
 255          * following fields may be used.
 256          */
 257         struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
 258 };
 259
 260 /**
 261  * lib_ring_buffer_ctx_init - initialize ring buffer context
 262  * @ctx: ring buffer context to initialize
 263  * @chan: channel
 264  * @priv: client private data
 265  * @data_size: size of record data payload
 266  * @largest_align: largest alignment within data payload types
 267  * @cpu: processor id
 268  */
 269 static inline lttng_ust_notrace
 270 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 271                               struct channel *chan, void *priv,
 272                               size_t data_size, int largest_align,
 273                               int cpu, struct lttng_ust_shm_handle *handle,
 274                               void *priv2);
 275 static inline
 276 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 277                               struct channel *chan, void *priv,
 278                               size_t data_size, int largest_align,
 279                               int cpu, struct lttng_ust_shm_handle *handle,
 280                               void *priv2)
 281 {
 282         ctx->chan = chan;
 283         ctx->priv = priv;
 284         ctx->data_size = data_size;
 285         ctx->largest_align = largest_align;
 286         ctx->cpu = cpu;
 287         ctx->rflags = 0;
 288         ctx->handle = handle;
 289         ctx->ctx_len = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
 290         ctx->ip = 0;
 291         ctx->priv2 = priv2;
 292         memset(ctx->padding2, 0, LTTNG_UST_RING_BUFFER_CTX_PADDING);
 293 }
 294
 295 /*
 296  * Reservation flags.
 297  *
 298  * RING_BUFFER_RFLAG_FULL_TSC
 299  *
 300  * This flag is passed to record_header_size() and to the primitive used to
 301  * write the record header. It indicates that the full 64-bit time value is
 302  * needed in the record header. If this flag is not set, the record header needs
 303  * only to contain "tsc_bits" bit of time value.
 304  *
 305  * Reservation flags can be added by the client, starting from
 306  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 307  * record_header_size() to lib_ring_buffer_write_record_header().
 308  */
 309 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 310 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 311
 312 /*
 313  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 314  * compile-time. We have to duplicate the "config->align" information and the
 315  * definition here because config->align is used both in the slow and fast
 316  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 317  */
 318 #ifdef RING_BUFFER_ALIGN
 319
 320 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 321
 322 /*
 323  * Calculate the offset needed to align the type.
 324  * size_of_type must be non-zero.
 325  */
 326 static inline lttng_ust_notrace
 327 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 328 static inline
 329 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 330 {
 331         return lttng_ust_offset_align(align_drift, size_of_type);
 332 }
 333
 334 #else
 335
 336 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 337
 338 /*
 339  * Calculate the offset needed to align the type.
 340  * size_of_type must be non-zero.
 341  */
 342 static inline lttng_ust_notrace
 343 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 344 static inline
 345 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 346 {
 347         return 0;
 348 }
 349
 350 #endif
 351
 352 /**
 353  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 354  * @ctx: ring buffer context.
 355  */
 356 static inline lttng_ust_notrace
 357 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 358                            size_t alignment);
 359 static inline
 360 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 361                            size_t alignment)
 362 {
 363         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 364                                                  alignment);
 365 }
 366
 367 /*
 368  * lib_ring_buffer_check_config() returns 0 on success.
 369  * Used internally to check for valid configurations at channel creation.
 370  */
 371 static inline lttng_ust_notrace
 372 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 373                              unsigned int switch_timer_interval,
 374                              unsigned int read_timer_interval);
 375 static inline
 376 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 377                              unsigned int switch_timer_interval,
 378                              unsigned int read_timer_interval)
 379 {
 380         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 381             && config->sync == RING_BUFFER_SYNC_PER_CPU
 382             && switch_timer_interval)
 383                 return -EINVAL;
 384         return 0;
 385 }
 386
 387 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */