lib/ringbuffer/config.h

   1 #ifndef _LIB_RING_BUFFER_CONFIG_H
   2 #define _LIB_RING_BUFFER_CONFIG_H
   3
   4 /*
   5  * lib/ringbuffer/config.h
   6  *
   7  * Ring buffer configuration header. Note: after declaring the standard inline
   8  * functions, clients should also include linux/ringbuffer/api.h.
   9  *
  10  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  11  *
  12  * This library is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public
  14  * License as published by the Free Software Foundation; only
  15  * version 2.1 of the License.
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  20  * Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this library; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  25  */
  26
  27 #include <linux/types.h>
  28 #include <linux/percpu.h>
  29 #include "../align.h"
  30
  31 struct lib_ring_buffer;
  32 struct channel;
  33 struct lib_ring_buffer_config;
  34 struct lib_ring_buffer_ctx;
  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 lib_ring_buffer_client_cb {
  43         /* Mandatory callbacks */
  44
  45         /* A static inline version is also required for fast path */
  46         u64 (*ring_buffer_clock_read) (struct channel *chan);
  47         size_t (*record_header_size) (const struct lib_ring_buffer_config *config,
  48                                       struct channel *chan, size_t offset,
  49                                       size_t *pre_header_padding,
  50                                       struct 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 lib_ring_buffer *buf, u64 tsc,
  55                               unsigned int subbuf_idx);
  56         void (*buffer_end) (struct lib_ring_buffer *buf, u64 tsc,
  57                             unsigned int subbuf_idx, unsigned long data_size);
  58
  59         /* Optional callbacks (can be set to NULL) */
  60
  61         /* Called at buffer creation/finalize */
  62         int (*buffer_create) (struct lib_ring_buffer *buf, void *priv,
  63                               int cpu, const char *name);
  64         /*
  65          * Clients should guarantee that no new reader handle can be opened
  66          * after finalize.
  67          */
  68         void (*buffer_finalize) (struct lib_ring_buffer *buf, void *priv, int cpu);
  69
  70         /*
  71          * Extract header length, payload length and timestamp from event
  72          * record. Used by buffer iterators. Timestamp is only used by channel
  73          * iterator.
  74          */
  75         void (*record_get) (const struct lib_ring_buffer_config *config,
  76                             struct channel *chan, struct lib_ring_buffer *buf,
  77                             size_t offset, size_t *header_len,
  78                             size_t *payload_len, u64 *timestamp);
  79 };
  80
  81 /*
  82  * Ring buffer instance configuration.
  83  *
  84  * Declare as "static const" within the client object to ensure the inline fast
  85  * paths can be optimized.
  86  *
  87  * alloc/sync pairs:
  88  *
  89  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  90  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  91  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  92  *   lib_ring_buffer_put_cpu()).
  93  *
  94  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  95  *   Per-cpu buffer with global synchronization. Tracing can be performed with
  96  *   preemption enabled, statistically stays on the local buffers.
  97  *
  98  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
  99  *   Should only be used for buffers belonging to a single thread or protected
 100  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 101  *   should be disabled in this kind of configuration.
 102  *
 103  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 104  *   Global shared buffer with global synchronization.
 105  *
 106  * wakeup:
 107  *
 108  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu deferrable timers to poll the
 109  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 110  * don't want to call into the wakeup code on the tracing path. Use in
 111  * combination with "read_timer_interval" channel_create() argument.
 112  *
 113  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 114  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 115  * for drivers.
 116  *
 117  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 118  * has the responsibility to perform wakeups.
 119  */
 120 struct lib_ring_buffer_config {
 121         enum {
 122                 RING_BUFFER_ALLOC_PER_CPU,
 123                 RING_BUFFER_ALLOC_GLOBAL,
 124         } alloc;
 125         enum {
 126                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 127                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 128         } sync;
 129         enum {
 130                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 131                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 132         } mode;
 133         enum {
 134                 RING_BUFFER_SPLICE,
 135                 RING_BUFFER_MMAP,
 136                 RING_BUFFER_READ,               /* TODO */
 137                 RING_BUFFER_ITERATOR,
 138                 RING_BUFFER_NONE,
 139         } output;
 140         enum {
 141                 RING_BUFFER_PAGE,
 142                 RING_BUFFER_VMAP,               /* TODO */
 143                 RING_BUFFER_STATIC,             /* TODO */
 144         } backend;
 145         enum {
 146                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 147                 RING_BUFFER_OOPS_CONSISTENCY,
 148         } oops;
 149         enum {
 150                 RING_BUFFER_IPI_BARRIER,
 151                 RING_BUFFER_NO_IPI_BARRIER,
 152         } ipi;
 153         enum {
 154                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 155                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 156                                                  * writer wakes up reader,
 157                                                  * not lock-free
 158                                                  * (takes spinlock).
 159                                                  */
 160         } wakeup;
 161         /*
 162          * tsc_bits: timestamp bits saved at each record.
 163          *   0 and 64 disable the timestamp compression scheme.
 164          */
 165         unsigned int tsc_bits;
 166         struct lib_ring_buffer_client_cb cb;
 167 };
 168
 169 /*
 170  * ring buffer context
 171  *
 172  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 173  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 174  * lib_ring_buffer_write().
 175  */
 176 struct lib_ring_buffer_ctx {
 177         /* input received by lib_ring_buffer_reserve(), saved here. */
 178         struct channel *chan;           /* channel */
 179         void *priv;                     /* client private data */
 180         size_t data_size;               /* size of payload */
 181         int largest_align;              /*
 182                                          * alignment of the largest element
 183                                          * in the payload
 184                                          */
 185         int cpu;                        /* processor id */
 186
 187         /* output from lib_ring_buffer_reserve() */
 188         struct lib_ring_buffer *buf;    /*
 189                                          * buffer corresponding to processor id
 190                                          * for this channel
 191                                          */
 192         size_t slot_size;               /* size of the reserved slot */
 193         unsigned long buf_offset;       /* offset following the record header */
 194         unsigned long pre_offset;       /*
 195                                          * Initial offset position _before_
 196                                          * the record is written. Positioned
 197                                          * prior to record header alignment
 198                                          * padding.
 199                                          */
 200         u64 tsc;                        /* time-stamp counter value */
 201         unsigned int rflags;            /* reservation flags */
 202 };
 203
 204 /**
 205  * lib_ring_buffer_ctx_init - initialize ring buffer context
 206  * @ctx: ring buffer context to initialize
 207  * @chan: channel
 208  * @priv: client private data
 209  * @data_size: size of record data payload
 210  * @largest_align: largest alignment within data payload types
 211  * @cpu: processor id
 212  */
 213 static inline
 214 void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx *ctx,
 215                               struct channel *chan, void *priv,
 216                               size_t data_size, int largest_align,
 217                               int cpu)
 218 {
 219         ctx->chan = chan;
 220         ctx->priv = priv;
 221         ctx->data_size = data_size;
 222         ctx->largest_align = largest_align;
 223         ctx->cpu = cpu;
 224         ctx->rflags = 0;
 225 }
 226
 227 /*
 228  * Reservation flags.
 229  *
 230  * RING_BUFFER_RFLAG_FULL_TSC
 231  *
 232  * This flag is passed to record_header_size() and to the primitive used to
 233  * write the record header. It indicates that the full 64-bit time value is
 234  * needed in the record header. If this flag is not set, the record header needs
 235  * only to contain "tsc_bits" bit of time value.
 236  *
 237  * Reservation flags can be added by the client, starting from
 238  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 239  * record_header_size() to lib_ring_buffer_write_record_header().
 240  */
 241 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 242 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 243
 244 /*
 245  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 246  * compile-time. We have to duplicate the "config->align" information and the
 247  * definition here because config->align is used both in the slow and fast
 248  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 249  */
 250 #ifdef RING_BUFFER_ALIGN
 251
 252 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 253
 254 /*
 255  * Calculate the offset needed to align the type.
 256  * size_of_type must be non-zero.
 257  */
 258 static inline
 259 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 260 {
 261         return offset_align(align_drift, size_of_type);
 262 }
 263
 264 #else
 265
 266 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 267
 268 /*
 269  * Calculate the offset needed to align the type.
 270  * size_of_type must be non-zero.
 271  */
 272 static inline
 273 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 274 {
 275         return 0;
 276 }
 277
 278 #endif
 279
 280 /**
 281  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 282  * @ctx: ring buffer context.
 283  */
 284 static inline
 285 void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx *ctx,
 286                            size_t alignment)
 287 {
 288         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 289                                                  alignment);
 290 }
 291
 292 /*
 293  * lib_ring_buffer_check_config() returns 0 on success.
 294  * Used internally to check for valid configurations at channel creation.
 295  */
 296 static inline
 297 int lib_ring_buffer_check_config(const struct lib_ring_buffer_config *config,
 298                              unsigned int switch_timer_interval,
 299                              unsigned int read_timer_interval)
 300 {
 301         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 302             && config->sync == RING_BUFFER_SYNC_PER_CPU
 303             && switch_timer_interval)
 304                 return -EINVAL;
 305         return 0;
 306 }
 307
 308 #include "../../wrapper/ringbuffer/vatomic.h"
 309
 310 #endif /* _LIB_RING_BUFFER_CONFIG_H */