include/lttng/ringbuffer-config.h

   1 #ifndef _LINUX_RING_BUFFER_CONFIG_H
   2 #define _LINUX_RING_BUFFER_CONFIG_H
   3
   4 /*
   5  * linux/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  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
  13  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
  14  *
  15  * Permission is hereby granted to use or copy this program
  16  * for any purpose,  provided the above notices are retained on all copies.
  17  * Permission to modify the code and to distribute modified code is granted,
  18  * provided the above notices are retained, and a notice that the code was
  19  * modified is included with the above copyright notice.
  20  */
  21
  22 #include <errno.h>
  23 #include "lttng/ust-tracer.h"
  24 #include <stdint.h>
  25 #include <stddef.h>
  26 #include <urcu/arch.h>
  27 #include "lttng/align.h"
  28
  29 struct lttng_ust_lib_ring_buffer;
  30 struct channel;
  31 struct lttng_ust_lib_ring_buffer_config;
  32 struct lttng_ust_lib_ring_buffer_ctx;
  33 struct lttng_ust_shm_handle *handle;
  34
  35 /*
  36  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  37  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  38  * provided as inline functions too.  These may simply return 0 if not used by
  39  * the client.
  40  */
  41 struct lttng_ust_lib_ring_buffer_client_cb {
  42         /* Mandatory callbacks */
  43
  44         /* A static inline version is also required for fast path */
  45         uint64_t (*ring_buffer_clock_read) (struct channel *chan);
  46         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  47                                       struct channel *chan, size_t offset,
  48                                       size_t *pre_header_padding,
  49                                       struct lttng_ust_lib_ring_buffer_ctx *ctx);
  50
  51         /* Slow path only, at subbuffer switch */
  52         size_t (*subbuffer_header_size) (void);
  53         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  54                               unsigned int subbuf_idx,
  55                               struct lttng_ust_shm_handle *handle);
  56         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc,
  57                             unsigned int subbuf_idx, unsigned long data_size,
  58                             struct lttng_ust_shm_handle *handle);
  59
  60         /* Optional callbacks (can be set to NULL) */
  61
  62         /* Called at buffer creation/finalize */
  63         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  64                               int cpu, const char *name,
  65                               struct lttng_ust_shm_handle *handle);
  66         /*
  67          * Clients should guarantee that no new reader handle can be opened
  68          * after finalize.
  69          */
  70         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  71                                  void *priv, int cpu,
  72                                  struct lttng_ust_shm_handle *handle);
  73
  74         /*
  75          * Extract header length, payload length and timestamp from event
  76          * record. Used by buffer iterators. Timestamp is only used by channel
  77          * iterator.
  78          */
  79         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  80                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  81                             size_t offset, size_t *header_len,
  82                             size_t *payload_len, uint64_t *timestamp,
  83                             struct lttng_ust_shm_handle *handle);
  84 };
  85
  86 /*
  87  * Ring buffer instance configuration.
  88  *
  89  * Declare as "static const" within the client object to ensure the inline fast
  90  * paths can be optimized.
  91  *
  92  * alloc/sync pairs:
  93  *
  94  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  95  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  96  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  97  *   lib_ring_buffer_put_cpu()).
  98  *
  99  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
 100  *   Per-cpu buffer with global synchronization. Tracing can be performed with
 101  *   preemption enabled, statistically stays on the local buffers.
 102  *
 103  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 104  *   Should only be used for buffers belonging to a single thread or protected
 105  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 106  *   should be disabled in this kind of configuration.
 107  *
 108  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 109  *   Global shared buffer with global synchronization.
 110  *
 111  * wakeup:
 112  *
 113  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 114  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 115  * don't want to call into the wakeup code on the tracing path. Use in
 116  * combination with "read_timer_interval" channel_create() argument.
 117  *
 118  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 119  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 120  * for drivers.
 121  *
 122  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 123  * has the responsibility to perform wakeups.
 124  */
 125 struct lttng_ust_lib_ring_buffer_config {
 126         enum {
 127                 RING_BUFFER_ALLOC_PER_CPU,
 128                 RING_BUFFER_ALLOC_GLOBAL,
 129         } alloc;
 130         enum {
 131                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 132                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 133         } sync;
 134         enum {
 135                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 136                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 137         } mode;
 138         enum {
 139                 RING_BUFFER_SPLICE,
 140                 RING_BUFFER_MMAP,
 141                 RING_BUFFER_READ,               /* TODO */
 142                 RING_BUFFER_ITERATOR,
 143                 RING_BUFFER_NONE,
 144         } output;
 145         enum {
 146                 RING_BUFFER_PAGE,
 147                 RING_BUFFER_VMAP,               /* TODO */
 148                 RING_BUFFER_STATIC,             /* TODO */
 149         } backend;
 150         enum {
 151                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 152                 RING_BUFFER_OOPS_CONSISTENCY,
 153         } oops;
 154         enum {
 155                 RING_BUFFER_IPI_BARRIER,
 156                 RING_BUFFER_NO_IPI_BARRIER,
 157         } ipi;
 158         enum {
 159                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 160                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 161                                                  * writer wakes up reader,
 162                                                  * not lock-free
 163                                                  * (takes spinlock).
 164                                                  */
 165         } wakeup;
 166         /*
 167          * tsc_bits: timestamp bits saved at each record.
 168          *   0 and 64 disable the timestamp compression scheme.
 169          */
 170         unsigned int tsc_bits;
 171         struct lttng_ust_lib_ring_buffer_client_cb cb;
 172         /*
 173          * client_type is used by the consumer process (which is in a
 174          * different address space) to lookup the appropriate client
 175          * callbacks and update the cb pointers.
 176          */
 177         int client_type;
 178 };
 179
 180 /*
 181  * ring buffer context
 182  *
 183  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 184  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 185  * lib_ring_buffer_write().
 186  */
 187 struct lttng_ust_lib_ring_buffer_ctx {
 188         /* input received by lib_ring_buffer_reserve(), saved here. */
 189         struct channel *chan;           /* channel */
 190         void *priv;                     /* client private data */
 191         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 192         size_t data_size;               /* size of payload */
 193         int largest_align;              /*
 194                                          * alignment of the largest element
 195                                          * in the payload
 196                                          */
 197         int cpu;                        /* processor id */
 198
 199         /* output from lib_ring_buffer_reserve() */
 200         struct lttng_ust_lib_ring_buffer *buf;  /*
 201                                          * buffer corresponding to processor id
 202                                          * for this channel
 203                                          */
 204         size_t slot_size;               /* size of the reserved slot */
 205         unsigned long buf_offset;       /* offset following the record header */
 206         unsigned long pre_offset;       /*
 207                                          * Initial offset position _before_
 208                                          * the record is written. Positioned
 209                                          * prior to record header alignment
 210                                          * padding.
 211                                          */
 212         uint64_t tsc;                   /* time-stamp counter value */
 213         unsigned int rflags;            /* reservation flags */
 214 };
 215
 216 /**
 217  * lib_ring_buffer_ctx_init - initialize ring buffer context
 218  * @ctx: ring buffer context to initialize
 219  * @chan: channel
 220  * @priv: client private data
 221  * @data_size: size of record data payload
 222  * @largest_align: largest alignment within data payload types
 223  * @cpu: processor id
 224  */
 225 static inline
 226 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 227                               struct channel *chan, void *priv,
 228                               size_t data_size, int largest_align,
 229                               int cpu, struct lttng_ust_shm_handle *handle)
 230 {
 231         ctx->chan = chan;
 232         ctx->priv = priv;
 233         ctx->data_size = data_size;
 234         ctx->largest_align = largest_align;
 235         ctx->cpu = cpu;
 236         ctx->rflags = 0;
 237         ctx->handle = handle;
 238 }
 239
 240 /*
 241  * Reservation flags.
 242  *
 243  * RING_BUFFER_RFLAG_FULL_TSC
 244  *
 245  * This flag is passed to record_header_size() and to the primitive used to
 246  * write the record header. It indicates that the full 64-bit time value is
 247  * needed in the record header. If this flag is not set, the record header needs
 248  * only to contain "tsc_bits" bit of time value.
 249  *
 250  * Reservation flags can be added by the client, starting from
 251  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 252  * record_header_size() to lib_ring_buffer_write_record_header().
 253  */
 254 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 255 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 256
 257 /*
 258  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 259  * compile-time. We have to duplicate the "config->align" information and the
 260  * definition here because config->align is used both in the slow and fast
 261  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 262  */
 263 #ifdef RING_BUFFER_ALIGN
 264
 265 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 266
 267 /*
 268  * Calculate the offset needed to align the type.
 269  * size_of_type must be non-zero.
 270  */
 271 static inline
 272 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 273 {
 274         return offset_align(align_drift, size_of_type);
 275 }
 276
 277 #else
 278
 279 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 280
 281 /*
 282  * Calculate the offset needed to align the type.
 283  * size_of_type must be non-zero.
 284  */
 285 static inline
 286 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 287 {
 288         return 0;
 289 }
 290
 291 #endif
 292
 293 /**
 294  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 295  * @ctx: ring buffer context.
 296  */
 297 static inline
 298 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 299                            size_t alignment)
 300 {
 301         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 302                                                  alignment);
 303 }
 304
 305 /*
 306  * lib_ring_buffer_check_config() returns 0 on success.
 307  * Used internally to check for valid configurations at channel creation.
 308  */
 309 static inline
 310 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 311                              unsigned int switch_timer_interval,
 312                              unsigned int read_timer_interval)
 313 {
 314         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 315             && config->sync == RING_BUFFER_SYNC_PER_CPU
 316             && switch_timer_interval)
 317                 return -EINVAL;
 318         return 0;
 319 }
 320
 321 #endif /* _LINUX_RING_BUFFER_CONFIG_H */