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 #define LTTNG_UST_RING_BUFFER_CTX_PADDING       24
 193 struct lttng_ust_lib_ring_buffer_ctx {
 194         /* input received by lib_ring_buffer_reserve(), saved here. */
 195         struct channel *chan;           /* channel */
 196         void *priv;                     /* client private data */
 197         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 198         size_t data_size;               /* size of payload */
 199         int largest_align;              /*
 200                                          * alignment of the largest element
 201                                          * in the payload
 202                                          */
 203         int cpu;                        /* processor id */
 204
 205         /* output from lib_ring_buffer_reserve() */
 206         struct lttng_ust_lib_ring_buffer *buf;  /*
 207                                          * buffer corresponding to processor id
 208                                          * for this channel
 209                                          */
 210         size_t slot_size;               /* size of the reserved slot */
 211         unsigned long buf_offset;       /* offset following the record header */
 212         unsigned long pre_offset;       /*
 213                                          * Initial offset position _before_
 214                                          * the record is written. Positioned
 215                                          * prior to record header alignment
 216                                          * padding.
 217                                          */
 218         uint64_t tsc;                   /* time-stamp counter value */
 219         unsigned int rflags;            /* reservation flags */
 220         char padding[LTTNG_UST_RING_BUFFER_CTX_PADDING];
 221 };
 222
 223 /**
 224  * lib_ring_buffer_ctx_init - initialize ring buffer context
 225  * @ctx: ring buffer context to initialize
 226  * @chan: channel
 227  * @priv: client private data
 228  * @data_size: size of record data payload
 229  * @largest_align: largest alignment within data payload types
 230  * @cpu: processor id
 231  */
 232 static inline lttng_ust_notrace
 233 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 234                               struct channel *chan, void *priv,
 235                               size_t data_size, int largest_align,
 236                               int cpu, struct lttng_ust_shm_handle *handle);
 237 static inline
 238 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 239                               struct channel *chan, void *priv,
 240                               size_t data_size, int largest_align,
 241                               int cpu, struct lttng_ust_shm_handle *handle)
 242 {
 243         ctx->chan = chan;
 244         ctx->priv = priv;
 245         ctx->data_size = data_size;
 246         ctx->largest_align = largest_align;
 247         ctx->cpu = cpu;
 248         ctx->rflags = 0;
 249         ctx->handle = handle;
 250         memset(ctx->padding, 0, LTTNG_UST_RING_BUFFER_CTX_PADDING);
 251 }
 252
 253 /*
 254  * Reservation flags.
 255  *
 256  * RING_BUFFER_RFLAG_FULL_TSC
 257  *
 258  * This flag is passed to record_header_size() and to the primitive used to
 259  * write the record header. It indicates that the full 64-bit time value is
 260  * needed in the record header. If this flag is not set, the record header needs
 261  * only to contain "tsc_bits" bit of time value.
 262  *
 263  * Reservation flags can be added by the client, starting from
 264  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 265  * record_header_size() to lib_ring_buffer_write_record_header().
 266  */
 267 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 268 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 269
 270 /*
 271  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 272  * compile-time. We have to duplicate the "config->align" information and the
 273  * definition here because config->align is used both in the slow and fast
 274  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 275  */
 276 #ifdef RING_BUFFER_ALIGN
 277
 278 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 279
 280 /*
 281  * Calculate the offset needed to align the type.
 282  * size_of_type must be non-zero.
 283  */
 284 static inline lttng_ust_notrace
 285 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 286 static inline
 287 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 288 {
 289         return offset_align(align_drift, size_of_type);
 290 }
 291
 292 #else
 293
 294 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 295
 296 /*
 297  * Calculate the offset needed to align the type.
 298  * size_of_type must be non-zero.
 299  */
 300 static inline lttng_ust_notrace
 301 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type);
 302 static inline
 303 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 304 {
 305         return 0;
 306 }
 307
 308 #endif
 309
 310 /**
 311  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 312  * @ctx: ring buffer context.
 313  */
 314 static inline lttng_ust_notrace
 315 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 316                            size_t alignment);
 317 static inline
 318 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 319                            size_t alignment)
 320 {
 321         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 322                                                  alignment);
 323 }
 324
 325 /*
 326  * lib_ring_buffer_check_config() returns 0 on success.
 327  * Used internally to check for valid configurations at channel creation.
 328  */
 329 static inline lttng_ust_notrace
 330 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 331                              unsigned int switch_timer_interval,
 332                              unsigned int read_timer_interval);
 333 static inline
 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 {
 338         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 339             && config->sync == RING_BUFFER_SYNC_PER_CPU
 340             && switch_timer_interval)
 341                 return -EINVAL;
 342         return 0;
 343 }
 344
 345 #endif /* _LTTNG_RING_BUFFER_CONFIG_H */