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 #include <lttng/ust-compiler.h>
  31
  32 struct lttng_ust_lib_ring_buffer;
  33 struct channel;
  34 struct lttng_ust_lib_ring_buffer_config;
  35 struct lttng_ust_lib_ring_buffer_ctx;
  36 struct lttng_ust_shm_handle;
  37
  38 /*
  39  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  40  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  41  * provided as inline functions too.  These may simply return 0 if not used by
  42  * the client.
  43  */
  44 struct lttng_ust_lib_ring_buffer_client_cb {
  45         /* Mandatory callbacks */
  46
  47         /* A static inline version is also required for fast path */
  48         uint64_t (*ring_buffer_clock_read) (struct channel *chan);
  49         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  50                                       struct channel *chan, size_t offset,
  51                                       size_t *pre_header_padding,
  52                                       struct lttng_ust_lib_ring_buffer_ctx *ctx);
  53
  54         /* Slow path only, at subbuffer switch */
  55         size_t (*subbuffer_header_size) (void);
  56         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  57                               unsigned int subbuf_idx,
  58                               struct lttng_ust_shm_handle *handle);
  59         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  60                             unsigned int subbuf_idx, unsigned long data_size,
  61                             struct lttng_ust_shm_handle *handle);
  62
  63         /* Optional callbacks (can be set to NULL) */
  64
  65         /* Called at buffer creation/finalize */
  66         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  67                               int cpu, const char *name,
  68                               struct lttng_ust_shm_handle *handle);
  69         /*
  70          * Clients should guarantee that no new reader handle can be opened
  71          * after finalize.
  72          */
  73         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  74                                  void *priv, int cpu,
  75                                  struct lttng_ust_shm_handle *handle);
  76
  77         /*
  78          * Extract header length, payload length and timestamp from event
  79          * record. Used by buffer iterators. Timestamp is only used by channel
  80          * iterator.
  81          */
  82         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  83                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  84                             size_t offset, size_t *header_len,
  85                             size_t *payload_len, uint64_t *timestamp,
  86                             struct lttng_ust_shm_handle *handle);
  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    32
 129 struct lttng_ust_lib_ring_buffer_config {
 130         enum {
 131                 RING_BUFFER_ALLOC_PER_CPU,
 132                 RING_BUFFER_ALLOC_GLOBAL,
 133         } alloc;
 134         enum {
 135                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 136                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 137         } sync;
 138         enum {
 139                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 140                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 141         } mode;
 142         enum {
 143                 RING_BUFFER_SPLICE,
 144                 RING_BUFFER_MMAP,
 145                 RING_BUFFER_READ,               /* TODO */
 146                 RING_BUFFER_ITERATOR,
 147                 RING_BUFFER_NONE,
 148         } output;
 149         enum {
 150                 RING_BUFFER_PAGE,
 151                 RING_BUFFER_VMAP,               /* TODO */
 152                 RING_BUFFER_STATIC,             /* TODO */
 153         } backend;
 154         enum {
 155                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 156                 RING_BUFFER_OOPS_CONSISTENCY,
 157         } oops;
 158         enum {
 159                 RING_BUFFER_IPI_BARRIER,
 160                 RING_BUFFER_NO_IPI_BARRIER,
 161         } ipi;
 162         enum {
 163                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 164                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 165                                                  * writer wakes up reader,
 166                                                  * not lock-free
 167                                                  * (takes spinlock).
 168                                                  */
 169         } wakeup;
 170         /*
 171          * tsc_bits: timestamp bits saved at each record.
 172          *   0 and 64 disable the timestamp compression scheme.
 173          */
 174         unsigned int tsc_bits;
 175         struct lttng_ust_lib_ring_buffer_client_cb cb;
 176         /*
 177          * client_type is used by the consumer process (which is in a
 178          * different address space) to lookup the appropriate client
 179          * callbacks and update the cb pointers.
 180          */
 181         int client_type;
 182         char padding[LTTNG_UST_RING_BUFFER_CONFIG_PADDING];
 183 };
 184
 185 /*
 186  * ring buffer context
 187  *
 188  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 189  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 190  * lib_ring_buffer_write().
 191  *
 192  * IMPORTANT: this structure is part of the ABI between the probe and
 193  * UST. Fields need to be only added at the end, never reordered, never
 194  * removed.
 195  */
 196 #define LTTNG_UST_RING_BUFFER_CTX_PADDING       24
 197 struct lttng_ust_lib_ring_buffer_ctx {
 198         /* input received by lib_ring_buffer_reserve(), saved here. */
 199         struct channel *chan;           /* channel */
 200         void *priv;                     /* client private data */
 201         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 202         size_t data_size;               /* size of payload */
 203         int largest_align;              /*
 204                                          * alignment of the largest element
 205                                          * in the payload
 206                                          */
 207         int cpu;                        /* processor id */
 208
 209         /* output from lib_ring_buffer_reserve() */
 210         struct lttng_ust_lib_ring_buffer *buf;  /*
 211                                          * buffer corresponding to processor id
 212                                          * for this channel
 213                                          */
 214         size_t slot_size;               /* size of the reserved slot */
 215         unsigned long buf_offset;       /* offset following the record header */
 216         unsigned long pre_offset;       /*
 217                                          * Initial offset position _before_
 218                                          * the record is written. Positioned
 219                                          * prior to record header alignment
 220                                          * padding.
 221                                          */
 222         uint64_t tsc;                   /* time-stamp counter value */
 223         unsigned int rflags;            /* reservation flags */
 224         char padding[LTTNG_UST_RING_BUFFER_CTX_PADDING];
 225 };
 226
 227 /**
 228  * lib_ring_buffer_ctx_init - initialize ring buffer context
 229  * @ctx: ring buffer context to initialize
 230  * @chan: channel
 231  * @priv: client private data
 232  * @data_size: size of record data payload
 233  * @largest_align: largest alignment within data payload types
 234  * @cpu: processor id
 235  */
 236 static inline lttng_ust_notrace
 237 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 238                               struct channel *chan, void *priv,
 239                               size_t data_size, int largest_align,
 240                               int cpu, struct lttng_ust_shm_handle *handle);
 241 static inline
 242 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 243                               struct channel *chan, void *priv,
 244                               size_t data_size, int largest_align,
 245                               int cpu, struct lttng_ust_shm_handle *handle)
 246 {
 247         ctx->chan = chan;
 248         ctx->priv = priv;
 249         ctx->data_size = data_size;
 250         ctx->largest_align = largest_align;
 251         ctx->cpu = cpu;
 252         ctx->rflags = 0;
 253         ctx->handle = handle;
 254         memset(ctx->padding, 0, LTTNG_UST_RING_BUFFER_CTX_PADDING);
 255 }
 256
 257 /*
 258  * Reservation flags.
 259  *
 260  * RING_BUFFER_RFLAG_FULL_TSC
 261  *
 262  * This flag is passed to record_header_size() and to the primitive used to
 263  * write the record header. It indicates that the full 64-bit time value is
 264  * needed in the record header. If this flag is not set, the record header needs
 265  * only to contain "tsc_bits" bit of time value.
 266  *
 267  * Reservation flags can be added by the client, starting from
 268  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 269  * record_header_size() to lib_ring_buffer_write_record_header().
 270  */
 271 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 272 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 273
 274 /*
 275  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 276  * compile-time. We have to duplicate the "config->align" information and the
 277  * definition here because config->align is used both in the slow and fast
 278  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 279  */
 280 #ifdef RING_BUFFER_ALIGN
 281
 282 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 283
 284 /*
 285  * Calculate the offset needed to align the type.
 286  * size_of_type must be non-zero.
 287  */
 288 static inline lttng_ust_notrace
 289 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 290 static inline
 291 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 292 {
 293         return offset_align(align_drift, size_of_type);
 294 }
 295
 296 #else
 297
 298 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 299
 300 /*
 301  * Calculate the offset needed to align the type.
 302  * size_of_type must be non-zero.
 303  */
 304 static inline lttng_ust_notrace
 305 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 306 static inline
 307 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 308 {
 309         return 0;
 310 }
 311
 312 #endif
 313
 314 /**
 315  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 316  * @ctx: ring buffer context.
 317  */
 318 static inline lttng_ust_notrace
 319 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 320                            size_t alignment);
 321 static inline
 322 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 323                            size_t alignment)
 324 {
 325         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 326                                                  alignment);
 327 }
 328
 329 /*
 330  * lib_ring_buffer_check_config() returns 0 on success.
 331  * Used internally to check for valid configurations at channel creation.
 332  */
 333 static inline lttng_ust_notrace
 334 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 335                              unsigned int switch_timer_interval,
 336                              unsigned int read_timer_interval);
 337 static inline
 338 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 339                              unsigned int switch_timer_interval,
 340                              unsigned int read_timer_interval)
 341 {
 342         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 343             && config->sync == RING_BUFFER_SYNC_PER_CPU
 344             && switch_timer_interval)
 345                 return -EINVAL;
 346         return 0;
 347 }
 348
 349 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */