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 "lttng/usterr-signal-safe.h"
  25 #include "lttng/kcompat/kcompat.h"
  26 #include "lttng/align.h"
  27
  28 struct lttng_ust_lib_ring_buffer;
  29 struct channel;
  30 struct lttng_ust_lib_ring_buffer_config;
  31 struct lttng_ust_lib_ring_buffer_ctx;
  32 struct lttng_ust_shm_handle *handle;
  33
  34 /*
  35  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  36  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  37  * provided as inline functions too.  These may simply return 0 if not used by
  38  * the client.
  39  */
  40 struct lttng_ust_lib_ring_buffer_client_cb {
  41         /* Mandatory callbacks */
  42
  43         /* A static inline version is also required for fast path */
  44         u64 (*ring_buffer_clock_read) (struct channel *chan);
  45         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  46                                       struct channel *chan, size_t offset,
  47                                       size_t *pre_header_padding,
  48                                       struct lttng_ust_lib_ring_buffer_ctx *ctx);
  49
  50         /* Slow path only, at subbuffer switch */
  51         size_t (*subbuffer_header_size) (void);
  52         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
  53                               unsigned int subbuf_idx,
  54                               struct lttng_ust_shm_handle *handle);
  55         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
  56                             unsigned int subbuf_idx, unsigned long data_size,
  57                             struct lttng_ust_shm_handle *handle);
  58
  59         /* Optional callbacks (can be set to NULL) */
  60
  61         /* Called at buffer creation/finalize */
  62         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  63                               int cpu, const char *name,
  64                               struct lttng_ust_shm_handle *handle);
  65         /*
  66          * Clients should guarantee that no new reader handle can be opened
  67          * after finalize.
  68          */
  69         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  70                                  void *priv, int cpu,
  71                                  struct lttng_ust_shm_handle *handle);
  72
  73         /*
  74          * Extract header length, payload length and timestamp from event
  75          * record. Used by buffer iterators. Timestamp is only used by channel
  76          * iterator.
  77          */
  78         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  79                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  80                             size_t offset, size_t *header_len,
  81                             size_t *payload_len, u64 *timestamp,
  82                             struct lttng_ust_shm_handle *handle);
  83 };
  84
  85 /*
  86  * Ring buffer instance configuration.
  87  *
  88  * Declare as "static const" within the client object to ensure the inline fast
  89  * paths can be optimized.
  90  *
  91  * alloc/sync pairs:
  92  *
  93  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  94  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  95  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  96  *   lib_ring_buffer_put_cpu()).
  97  *
  98  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  99  *   Per-cpu buffer with global synchronization. Tracing can be performed with
 100  *   preemption enabled, statistically stays on the local buffers.
 101  *
 102  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 103  *   Should only be used for buffers belonging to a single thread or protected
 104  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 105  *   should be disabled in this kind of configuration.
 106  *
 107  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 108  *   Global shared buffer with global synchronization.
 109  *
 110  * wakeup:
 111  *
 112  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 113  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 114  * don't want to call into the wakeup code on the tracing path. Use in
 115  * combination with "read_timer_interval" channel_create() argument.
 116  *
 117  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 118  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 119  * for drivers.
 120  *
 121  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 122  * has the responsibility to perform wakeups.
 123  */
 124 struct lttng_ust_lib_ring_buffer_config {
 125         enum {
 126                 RING_BUFFER_ALLOC_PER_CPU,
 127                 RING_BUFFER_ALLOC_GLOBAL,
 128         } alloc;
 129         enum {
 130                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 131                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 132         } sync;
 133         enum {
 134                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 135                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 136         } mode;
 137         enum {
 138                 RING_BUFFER_SPLICE,
 139                 RING_BUFFER_MMAP,
 140                 RING_BUFFER_READ,               /* TODO */
 141                 RING_BUFFER_ITERATOR,
 142                 RING_BUFFER_NONE,
 143         } output;
 144         enum {
 145                 RING_BUFFER_PAGE,
 146                 RING_BUFFER_VMAP,               /* TODO */
 147                 RING_BUFFER_STATIC,             /* TODO */
 148         } backend;
 149         enum {
 150                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 151                 RING_BUFFER_OOPS_CONSISTENCY,
 152         } oops;
 153         enum {
 154                 RING_BUFFER_IPI_BARRIER,
 155                 RING_BUFFER_NO_IPI_BARRIER,
 156         } ipi;
 157         enum {
 158                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 159                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 160                                                  * writer wakes up reader,
 161                                                  * not lock-free
 162                                                  * (takes spinlock).
 163                                                  */
 164         } wakeup;
 165         /*
 166          * tsc_bits: timestamp bits saved at each record.
 167          *   0 and 64 disable the timestamp compression scheme.
 168          */
 169         unsigned int tsc_bits;
 170         struct lttng_ust_lib_ring_buffer_client_cb cb;
 171         /*
 172          * client_type is used by the consumer process (which is in a
 173          * different address space) to lookup the appropriate client
 174          * callbacks and update the cb pointers.
 175          */
 176         int client_type;
 177 };
 178
 179 /*
 180  * ring buffer context
 181  *
 182  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 183  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 184  * lib_ring_buffer_write().
 185  */
 186 struct lttng_ust_lib_ring_buffer_ctx {
 187         /* input received by lib_ring_buffer_reserve(), saved here. */
 188         struct channel *chan;           /* channel */
 189         void *priv;                     /* client private data */
 190         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 191         size_t data_size;               /* size of payload */
 192         int largest_align;              /*
 193                                          * alignment of the largest element
 194                                          * in the payload
 195                                          */
 196         int cpu;                        /* processor id */
 197
 198         /* output from lib_ring_buffer_reserve() */
 199         struct lttng_ust_lib_ring_buffer *buf;  /*
 200                                          * buffer corresponding to processor id
 201                                          * for this channel
 202                                          */
 203         size_t slot_size;               /* size of the reserved slot */
 204         unsigned long buf_offset;       /* offset following the record header */
 205         unsigned long pre_offset;       /*
 206                                          * Initial offset position _before_
 207                                          * the record is written. Positioned
 208                                          * prior to record header alignment
 209                                          * padding.
 210                                          */
 211         u64 tsc;                        /* time-stamp counter value */
 212         unsigned int rflags;            /* reservation flags */
 213 };
 214
 215 /**
 216  * lib_ring_buffer_ctx_init - initialize ring buffer context
 217  * @ctx: ring buffer context to initialize
 218  * @chan: channel
 219  * @priv: client private data
 220  * @data_size: size of record data payload
 221  * @largest_align: largest alignment within data payload types
 222  * @cpu: processor id
 223  */
 224 static inline
 225 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 226                               struct channel *chan, void *priv,
 227                               size_t data_size, int largest_align,
 228                               int cpu, struct lttng_ust_shm_handle *handle)
 229 {
 230         ctx->chan = chan;
 231         ctx->priv = priv;
 232         ctx->data_size = data_size;
 233         ctx->largest_align = largest_align;
 234         ctx->cpu = cpu;
 235         ctx->rflags = 0;
 236         ctx->handle = handle;
 237 }
 238
 239 /*
 240  * Reservation flags.
 241  *
 242  * RING_BUFFER_RFLAG_FULL_TSC
 243  *
 244  * This flag is passed to record_header_size() and to the primitive used to
 245  * write the record header. It indicates that the full 64-bit time value is
 246  * needed in the record header. If this flag is not set, the record header needs
 247  * only to contain "tsc_bits" bit of time value.
 248  *
 249  * Reservation flags can be added by the client, starting from
 250  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 251  * record_header_size() to lib_ring_buffer_write_record_header().
 252  */
 253 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 254 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 255
 256 /*
 257  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 258  * compile-time. We have to duplicate the "config->align" information and the
 259  * definition here because config->align is used both in the slow and fast
 260  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 261  */
 262 #ifdef RING_BUFFER_ALIGN
 263
 264 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 265
 266 /*
 267  * Calculate the offset needed to align the type.
 268  * size_of_type must be non-zero.
 269  */
 270 static inline
 271 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 272 {
 273         return offset_align(align_drift, size_of_type);
 274 }
 275
 276 #else
 277
 278 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 279
 280 /*
 281  * Calculate the offset needed to align the type.
 282  * size_of_type must be non-zero.
 283  */
 284 static inline
 285 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 286 {
 287         return 0;
 288 }
 289
 290 #endif
 291
 292 /**
 293  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 294  * @ctx: ring buffer context.
 295  */
 296 static inline
 297 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 298                            size_t alignment)
 299 {
 300         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 301                                                  alignment);
 302 }
 303
 304 /*
 305  * lib_ring_buffer_check_config() returns 0 on success.
 306  * Used internally to check for valid configurations at channel creation.
 307  */
 308 static inline
 309 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 310                              unsigned int switch_timer_interval,
 311                              unsigned int read_timer_interval)
 312 {
 313         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 314             && config->sync == RING_BUFFER_SYNC_PER_CPU
 315             && switch_timer_interval)
 316                 return -EINVAL;
 317         return 0;
 318 }
 319
 320 #include <lttng/vatomic.h>
 321
 322 #endif /* _LINUX_RING_BUFFER_CONFIG_H */