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