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 lttng_ust_lib_ring_buffer_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 lttng_ust_lib_ring_buffer_channel *chan);
  39         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  40                                       struct lttng_ust_lib_ring_buffer_channel *chan,
  41                                       size_t offset,
  42                                       size_t *pre_header_padding,
  43                                       struct lttng_ust_lib_ring_buffer_ctx *ctx,
  44                                       void *client_ctx);
  45
  46         /* Slow path only, at subbuffer switch */
  47         size_t (*subbuffer_header_size) (void);
  48         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  49                               unsigned int subbuf_idx,
  50                               struct lttng_ust_shm_handle *handle);
  51         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  52                             unsigned int subbuf_idx, unsigned long data_size,
  53                             struct lttng_ust_shm_handle *handle);
  54
  55         /* Optional callbacks (can be set to NULL) */
  56
  57         /* Called at buffer creation/finalize */
  58         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  59                               int cpu, const char *name,
  60                               struct lttng_ust_shm_handle *handle);
  61         /*
  62          * Clients should guarantee that no new reader handle can be opened
  63          * after finalize.
  64          */
  65         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  66                                  void *priv, int cpu,
  67                                  struct lttng_ust_shm_handle *handle);
  68
  69         /*
  70          * Extract header length, payload length and timestamp from event
  71          * record. Used by buffer iterators. Timestamp is only used by channel
  72          * iterator.
  73          */
  74         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  75                             struct lttng_ust_lib_ring_buffer_channel *chan,
  76                             struct lttng_ust_lib_ring_buffer *buf,
  77                             size_t offset, size_t *header_len,
  78                             size_t *payload_len, uint64_t *timestamp,
  79                             struct lttng_ust_shm_handle *handle);
  80         /*
  81          * Offset and size of content size field in client.
  82          */
  83         void (*content_size_field) (const struct lttng_ust_lib_ring_buffer_config *config,
  84                                 size_t *offset, size_t *length);
  85         void (*packet_size_field) (const struct lttng_ust_lib_ring_buffer_config *config,
  86                                 size_t *offset, size_t *length);
  87 };
  88
  89 /*
  90  * Ring buffer instance configuration.
  91  *
  92  * Declare as "static const" within the client object to ensure the inline fast
  93  * paths can be optimized.
  94  *
  95  * alloc/sync pairs:
  96  *
  97  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  98  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  99  *   with preemption disabled (lib_ring_buffer_get_cpu() and
 100  *   lib_ring_buffer_put_cpu()).
 101  *
 102  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
 103  *   Per-cpu buffer with global synchronization. Tracing can be performed with
 104  *   preemption enabled, statistically stays on the local buffers.
 105  *
 106  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 107  *   Should only be used for buffers belonging to a single thread or protected
 108  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 109  *   should be disabled in this kind of configuration.
 110  *
 111  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 112  *   Global shared buffer with global synchronization.
 113  *
 114  * wakeup:
 115  *
 116  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 117  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 118  * don't want to call into the wakeup code on the tracing path. Use in
 119  * combination with "read_timer_interval" channel_create() argument.
 120  *
 121  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 122  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 123  * for drivers.
 124  *
 125  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 126  * has the responsibility to perform wakeups.
 127  */
 128 #define LTTNG_UST_RING_BUFFER_CONFIG_PADDING    20
 129
 130 enum lttng_ust_lib_ring_buffer_alloc_types {
 131         RING_BUFFER_ALLOC_PER_CPU,
 132         RING_BUFFER_ALLOC_GLOBAL,
 133 };
 134
 135 enum lttng_ust_lib_ring_buffer_sync_types {
 136         RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 137         RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 138 };
 139
 140 enum lttng_ust_lib_ring_buffer_mode_types {
 141         RING_BUFFER_OVERWRITE = 0,      /* Overwrite when buffer full */
 142         RING_BUFFER_DISCARD = 1,        /* Discard when buffer full */
 143 };
 144
 145 enum lttng_ust_lib_ring_buffer_output_types {
 146         RING_BUFFER_SPLICE,
 147         RING_BUFFER_MMAP,
 148         RING_BUFFER_READ,               /* TODO */
 149         RING_BUFFER_ITERATOR,
 150         RING_BUFFER_NONE,
 151 };
 152
 153 enum lttng_ust_lib_ring_buffer_backend_types {
 154         RING_BUFFER_PAGE,
 155         RING_BUFFER_VMAP,               /* TODO */
 156         RING_BUFFER_STATIC,             /* TODO */
 157 };
 158
 159 enum lttng_ust_lib_ring_buffer_oops_types {
 160         RING_BUFFER_NO_OOPS_CONSISTENCY,
 161         RING_BUFFER_OOPS_CONSISTENCY,
 162 };
 163
 164 enum lttng_ust_lib_ring_buffer_ipi_types {
 165         RING_BUFFER_IPI_BARRIER,
 166         RING_BUFFER_NO_IPI_BARRIER,
 167 };
 168
 169 enum lttng_ust_lib_ring_buffer_wakeup_types {
 170         RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 171         RING_BUFFER_WAKEUP_BY_WRITER,   /*
 172                                          * writer wakes up reader,
 173                                          * not lock-free
 174                                          * (takes spinlock).
 175                                          */
 176 };
 177
 178 struct lttng_ust_lib_ring_buffer_config {
 179         enum lttng_ust_lib_ring_buffer_alloc_types alloc;
 180         enum lttng_ust_lib_ring_buffer_sync_types sync;
 181         enum lttng_ust_lib_ring_buffer_mode_types mode;
 182         enum lttng_ust_lib_ring_buffer_output_types output;
 183         enum lttng_ust_lib_ring_buffer_backend_types backend;
 184         enum lttng_ust_lib_ring_buffer_oops_types oops;
 185         enum lttng_ust_lib_ring_buffer_ipi_types ipi;
 186         enum lttng_ust_lib_ring_buffer_wakeup_types wakeup;
 187         /*
 188          * tsc_bits: timestamp bits saved at each record.
 189          *   0 and 64 disable the timestamp compression scheme.
 190          */
 191         unsigned int tsc_bits;
 192         struct lttng_ust_lib_ring_buffer_client_cb cb;
 193         /*
 194          * client_type is used by the consumer process (which is in a
 195          * different address space) to lookup the appropriate client
 196          * callbacks and update the cb pointers.
 197          */
 198         int client_type;
 199         int _unused1;
 200         const struct lttng_ust_lib_ring_buffer_client_cb *cb_ptr;
 201         char padding[LTTNG_UST_RING_BUFFER_CONFIG_PADDING];
 202 };
 203
 204 /*
 205  * ring buffer context
 206  *
 207  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 208  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 209  * lib_ring_buffer_write().
 210  *
 211  * IMPORTANT: this structure is part of the ABI between the probe and
 212  * UST. Fields need to be only added at the end, never reordered, never
 213  * removed.
 214  */
 215 #define LTTNG_UST_RING_BUFFER_CTX_PADDING       64
 216 struct lttng_ust_lib_ring_buffer_ctx {
 217         uint32_t struct_size;           /* Size of this structure. */
 218
 219         /* input received by lib_ring_buffer_reserve(), saved here. */
 220         struct lttng_ust_lib_ring_buffer_channel *chan; /* channel */
 221         void *priv;                     /* client private data */
 222         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 223         size_t data_size;               /* size of payload */
 224         int largest_align;              /*
 225                                          * alignment of the largest element
 226                                          * in the payload
 227                                          */
 228         int cpu;                        /* processor id */
 229
 230         /* output from lib_ring_buffer_reserve() */
 231         struct lttng_ust_lib_ring_buffer *buf;  /*
 232                                          * buffer corresponding to processor id
 233                                          * for this channel
 234                                          */
 235         size_t slot_size;               /* size of the reserved slot */
 236         unsigned long buf_offset;       /* offset following the record header */
 237         unsigned long pre_offset;       /*
 238                                          * Initial offset position _before_
 239                                          * the record is written. Positioned
 240                                          * prior to record header alignment
 241                                          * padding.
 242                                          */
 243         uint64_t tsc;                   /* time-stamp counter value */
 244         unsigned int rflags;            /* reservation flags */
 245         void *ip;                       /* caller ip address */
 246         struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages;
 247 };
 248
 249 /**
 250  * lib_ring_buffer_ctx_init - initialize ring buffer context
 251  * @ctx: ring buffer context to initialize
 252  * @chan: channel
 253  * @priv: client private data
 254  * @data_size: size of record data payload
 255  * @largest_align: largest alignment within data payload types
 256  * @cpu: processor id
 257  */
 258 static inline lttng_ust_notrace
 259 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 260                               struct lttng_ust_lib_ring_buffer_channel *chan,
 261                               void *priv, size_t data_size, int largest_align,
 262                               int cpu, struct lttng_ust_shm_handle *handle);
 263 static inline
 264 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 265                               struct lttng_ust_lib_ring_buffer_channel *chan,
 266                               void *priv, size_t data_size, int largest_align,
 267                               int cpu, struct lttng_ust_shm_handle *handle)
 268 {
 269         ctx->struct_size = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
 270         ctx->chan = chan;
 271         ctx->priv = priv;
 272         ctx->data_size = data_size;
 273         ctx->largest_align = largest_align;
 274         ctx->cpu = cpu;
 275         ctx->rflags = 0;
 276         ctx->handle = handle;
 277         ctx->ip = 0;
 278 }
 279
 280 /*
 281  * Reservation flags.
 282  *
 283  * RING_BUFFER_RFLAG_FULL_TSC
 284  *
 285  * This flag is passed to record_header_size() and to the primitive used to
 286  * write the record header. It indicates that the full 64-bit time value is
 287  * needed in the record header. If this flag is not set, the record header needs
 288  * only to contain "tsc_bits" bit of time value.
 289  *
 290  * Reservation flags can be added by the client, starting from
 291  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 292  * record_header_size() to lib_ring_buffer_write_record_header().
 293  */
 294 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 295 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 296
 297 /*
 298  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 299  * compile-time. We have to duplicate the "config->align" information and the
 300  * definition here because config->align is used both in the slow and fast
 301  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 302  */
 303 #ifdef RING_BUFFER_ALIGN
 304
 305 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 306
 307 /*
 308  * Calculate the offset needed to align the type.
 309  * size_of_type must be non-zero.
 310  */
 311 static inline lttng_ust_notrace
 312 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 313 static inline
 314 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 315 {
 316         return lttng_ust_offset_align(align_drift, size_of_type);
 317 }
 318
 319 #else
 320
 321 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 322
 323 /*
 324  * Calculate the offset needed to align the type.
 325  * size_of_type must be non-zero.
 326  */
 327 static inline lttng_ust_notrace
 328 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 329 static inline
 330 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 331 {
 332         return 0;
 333 }
 334
 335 #endif
 336
 337 /**
 338  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 339  * @ctx: ring buffer context.
 340  */
 341 static inline lttng_ust_notrace
 342 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 343                            size_t alignment);
 344 static inline
 345 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 346                            size_t alignment)
 347 {
 348         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 349                                                  alignment);
 350 }
 351
 352 /*
 353  * lib_ring_buffer_check_config() returns 0 on success.
 354  * Used internally to check for valid configurations at channel creation.
 355  */
 356 static inline lttng_ust_notrace
 357 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 358                              unsigned int switch_timer_interval,
 359                              unsigned int read_timer_interval);
 360 static inline
 361 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 362                              unsigned int switch_timer_interval,
 363                              unsigned int read_timer_interval)
 364 {
 365         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 366             && config->sync == RING_BUFFER_SYNC_PER_CPU
 367             && switch_timer_interval)
 368                 return -EINVAL;
 369         return 0;
 370 }
 371
 372 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */