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