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