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