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  * Dual LGPL v2.1/GPL v2 license.
  13  */
  14
  15 #include <errno.h>
  16 #include "lttng/ust-tracer.h"
  17 #include "lttng/usterr-signal-safe.h"
  18 #include "lttng/kcompat/kcompat.h"
  19 #include "lttng/align.h"
  20
  21 struct lttng_ust_lib_ring_buffer;
  22 struct channel;
  23 struct lttng_ust_lib_ring_buffer_config;
  24 struct lttng_ust_lib_ring_buffer_ctx;
  25 struct lttng_ust_shm_handle *handle;
  26
  27 /*
  28  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  29  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  30  * provided as inline functions too.  These may simply return 0 if not used by
  31  * the client.
  32  */
  33 struct lttng_ust_lib_ring_buffer_client_cb {
  34         /* Mandatory callbacks */
  35
  36         /* A static inline version is also required for fast path */
  37         u64 (*ring_buffer_clock_read) (struct channel *chan);
  38         size_t (*record_header_size) (const struct lttng_ust_lib_ring_buffer_config *config,
  39                                       struct channel *chan, size_t offset,
  40                                       size_t *pre_header_padding,
  41                                       struct lttng_ust_lib_ring_buffer_ctx *ctx);
  42
  43         /* Slow path only, at subbuffer switch */
  44         size_t (*subbuffer_header_size) (void);
  45         void (*buffer_begin) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
  46                               unsigned int subbuf_idx,
  47                               struct lttng_ust_shm_handle *handle);
  48         void (*buffer_end) (struct lttng_ust_lib_ring_buffer *buf, u64 tsc,
  49                             unsigned int subbuf_idx, unsigned long data_size,
  50                             struct lttng_ust_shm_handle *handle);
  51
  52         /* Optional callbacks (can be set to NULL) */
  53
  54         /* Called at buffer creation/finalize */
  55         int (*buffer_create) (struct lttng_ust_lib_ring_buffer *buf, void *priv,
  56                               int cpu, const char *name,
  57                               struct lttng_ust_shm_handle *handle);
  58         /*
  59          * Clients should guarantee that no new reader handle can be opened
  60          * after finalize.
  61          */
  62         void (*buffer_finalize) (struct lttng_ust_lib_ring_buffer *buf,
  63                                  void *priv, int cpu,
  64                                  struct lttng_ust_shm_handle *handle);
  65
  66         /*
  67          * Extract header length, payload length and timestamp from event
  68          * record. Used by buffer iterators. Timestamp is only used by channel
  69          * iterator.
  70          */
  71         void (*record_get) (const struct lttng_ust_lib_ring_buffer_config *config,
  72                             struct channel *chan, struct lttng_ust_lib_ring_buffer *buf,
  73                             size_t offset, size_t *header_len,
  74                             size_t *payload_len, u64 *timestamp,
  75                             struct lttng_ust_shm_handle *handle);
  76 };
  77
  78 /*
  79  * Ring buffer instance configuration.
  80  *
  81  * Declare as "static const" within the client object to ensure the inline fast
  82  * paths can be optimized.
  83  *
  84  * alloc/sync pairs:
  85  *
  86  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  87  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  88  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  89  *   lib_ring_buffer_put_cpu()).
  90  *
  91  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  92  *   Per-cpu buffer with global synchronization. Tracing can be performed with
  93  *   preemption enabled, statistically stays on the local buffers.
  94  *
  95  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
  96  *   Should only be used for buffers belonging to a single thread or protected
  97  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
  98  *   should be disabled in this kind of configuration.
  99  *
 100  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 101  *   Global shared buffer with global synchronization.
 102  *
 103  * wakeup:
 104  *
 105  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 106  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 107  * don't want to call into the wakeup code on the tracing path. Use in
 108  * combination with "read_timer_interval" channel_create() argument.
 109  *
 110  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 111  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 112  * for drivers.
 113  *
 114  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 115  * has the responsibility to perform wakeups.
 116  */
 117 struct lttng_ust_lib_ring_buffer_config {
 118         enum {
 119                 RING_BUFFER_ALLOC_PER_CPU,
 120                 RING_BUFFER_ALLOC_GLOBAL,
 121         } alloc;
 122         enum {
 123                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 124                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 125         } sync;
 126         enum {
 127                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 128                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 129         } mode;
 130         enum {
 131                 RING_BUFFER_SPLICE,
 132                 RING_BUFFER_MMAP,
 133                 RING_BUFFER_READ,               /* TODO */
 134                 RING_BUFFER_ITERATOR,
 135                 RING_BUFFER_NONE,
 136         } output;
 137         enum {
 138                 RING_BUFFER_PAGE,
 139                 RING_BUFFER_VMAP,               /* TODO */
 140                 RING_BUFFER_STATIC,             /* TODO */
 141         } backend;
 142         enum {
 143                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 144                 RING_BUFFER_OOPS_CONSISTENCY,
 145         } oops;
 146         enum {
 147                 RING_BUFFER_IPI_BARRIER,
 148                 RING_BUFFER_NO_IPI_BARRIER,
 149         } ipi;
 150         enum {
 151                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 152                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 153                                                  * writer wakes up reader,
 154                                                  * not lock-free
 155                                                  * (takes spinlock).
 156                                                  */
 157         } wakeup;
 158         /*
 159          * tsc_bits: timestamp bits saved at each record.
 160          *   0 and 64 disable the timestamp compression scheme.
 161          */
 162         unsigned int tsc_bits;
 163         struct lttng_ust_lib_ring_buffer_client_cb cb;
 164         /*
 165          * client_type is used by the consumer process (which is in a
 166          * different address space) to lookup the appropriate client
 167          * callbacks and update the cb pointers.
 168          */
 169         int client_type;
 170 };
 171
 172 /*
 173  * ring buffer context
 174  *
 175  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 176  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 177  * lib_ring_buffer_write().
 178  */
 179 struct lttng_ust_lib_ring_buffer_ctx {
 180         /* input received by lib_ring_buffer_reserve(), saved here. */
 181         struct channel *chan;           /* channel */
 182         void *priv;                     /* client private data */
 183         struct lttng_ust_shm_handle *handle;    /* shared-memory handle */
 184         size_t data_size;               /* size of payload */
 185         int largest_align;              /*
 186                                          * alignment of the largest element
 187                                          * in the payload
 188                                          */
 189         int cpu;                        /* processor id */
 190
 191         /* output from lib_ring_buffer_reserve() */
 192         struct lttng_ust_lib_ring_buffer *buf;  /*
 193                                          * buffer corresponding to processor id
 194                                          * for this channel
 195                                          */
 196         size_t slot_size;               /* size of the reserved slot */
 197         unsigned long buf_offset;       /* offset following the record header */
 198         unsigned long pre_offset;       /*
 199                                          * Initial offset position _before_
 200                                          * the record is written. Positioned
 201                                          * prior to record header alignment
 202                                          * padding.
 203                                          */
 204         u64 tsc;                        /* time-stamp counter value */
 205         unsigned int rflags;            /* reservation flags */
 206 };
 207
 208 /**
 209  * lib_ring_buffer_ctx_init - initialize ring buffer context
 210  * @ctx: ring buffer context to initialize
 211  * @chan: channel
 212  * @priv: client private data
 213  * @data_size: size of record data payload
 214  * @largest_align: largest alignment within data payload types
 215  * @cpu: processor id
 216  */
 217 static inline
 218 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 219                               struct channel *chan, void *priv,
 220                               size_t data_size, int largest_align,
 221                               int cpu, struct lttng_ust_shm_handle *handle)
 222 {
 223         ctx->chan = chan;
 224         ctx->priv = priv;
 225         ctx->data_size = data_size;
 226         ctx->largest_align = largest_align;
 227         ctx->cpu = cpu;
 228         ctx->rflags = 0;
 229         ctx->handle = handle;
 230 }
 231
 232 /*
 233  * Reservation flags.
 234  *
 235  * RING_BUFFER_RFLAG_FULL_TSC
 236  *
 237  * This flag is passed to record_header_size() and to the primitive used to
 238  * write the record header. It indicates that the full 64-bit time value is
 239  * needed in the record header. If this flag is not set, the record header needs
 240  * only to contain "tsc_bits" bit of time value.
 241  *
 242  * Reservation flags can be added by the client, starting from
 243  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 244  * record_header_size() to lib_ring_buffer_write_record_header().
 245  */
 246 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 247 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 248
 249 /*
 250  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 251  * compile-time. We have to duplicate the "config->align" information and the
 252  * definition here because config->align is used both in the slow and fast
 253  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 254  */
 255 #ifdef RING_BUFFER_ALIGN
 256
 257 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 258
 259 /*
 260  * Calculate the offset needed to align the type.
 261  * size_of_type must be non-zero.
 262  */
 263 static inline
 264 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 265 {
 266         return offset_align(align_drift, size_of_type);
 267 }
 268
 269 #else
 270
 271 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 272
 273 /*
 274  * Calculate the offset needed to align the type.
 275  * size_of_type must be non-zero.
 276  */
 277 static inline
 278 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 279 {
 280         return 0;
 281 }
 282
 283 #endif
 284
 285 /**
 286  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 287  * @ctx: ring buffer context.
 288  */
 289 static inline
 290 void lib_ring_buffer_align_ctx(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 291                            size_t alignment)
 292 {
 293         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 294                                                  alignment);
 295 }
 296
 297 /*
 298  * lib_ring_buffer_check_config() returns 0 on success.
 299  * Used internally to check for valid configurations at channel creation.
 300  */
 301 static inline
 302 int lib_ring_buffer_check_config(const struct lttng_ust_lib_ring_buffer_config *config,
 303                              unsigned int switch_timer_interval,
 304                              unsigned int read_timer_interval)
 305 {
 306         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 307             && config->sync == RING_BUFFER_SYNC_PER_CPU
 308             && switch_timer_interval)
 309                 return -EINVAL;
 310         return 0;
 311 }
 312
 313 #include <lttng/vatomic.h>
 314
 315 #endif /* _LINUX_RING_BUFFER_CONFIG_H */