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