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 #include "../../lttng-tracer-core.h"
  31
  32 struct lib_ring_buffer;
  33 struct channel;
  34 struct lib_ring_buffer_config;
  35 struct lib_ring_buffer_ctx;
  36
  37 /*
  38  * Ring buffer client callbacks. Only used by slow path, never on fast path.
  39  * For the fast path, record_header_size(), ring_buffer_clock_read() should be
  40  * provided as inline functions too.  These may simply return 0 if not used by
  41  * the client.
  42  */
  43 struct lib_ring_buffer_client_cb {
  44         /* Mandatory callbacks */
  45
  46         /* A static inline version is also required for fast path */
  47         u64 (*ring_buffer_clock_read) (struct channel *chan);
  48         size_t (*record_header_size) (const struct lib_ring_buffer_config *config,
  49                                       struct channel *chan, size_t offset,
  50                                       size_t *pre_header_padding,
  51                                       struct lib_ring_buffer_ctx *ctx);
  52
  53         /* Slow path only, at subbuffer switch */
  54         size_t (*subbuffer_header_size) (void);
  55         void (*buffer_begin) (struct lib_ring_buffer *buf, u64 tsc,
  56                               unsigned int subbuf_idx);
  57         void (*buffer_end) (struct lib_ring_buffer *buf, u64 tsc,
  58                             unsigned int subbuf_idx, unsigned long data_size);
  59
  60         /* Optional callbacks (can be set to NULL) */
  61
  62         /* Called at buffer creation/finalize */
  63         int (*buffer_create) (struct lib_ring_buffer *buf, void *priv,
  64                               int cpu, const char *name);
  65         /*
  66          * Clients should guarantee that no new reader handle can be opened
  67          * after finalize.
  68          */
  69         void (*buffer_finalize) (struct lib_ring_buffer *buf, void *priv, int cpu);
  70
  71         /*
  72          * Extract header length, payload length and timestamp from event
  73          * record. Used by buffer iterators. Timestamp is only used by channel
  74          * iterator.
  75          */
  76         void (*record_get) (const struct lib_ring_buffer_config *config,
  77                             struct channel *chan, struct lib_ring_buffer *buf,
  78                             size_t offset, size_t *header_len,
  79                             size_t *payload_len, u64 *timestamp);
  80 };
  81
  82 /*
  83  * Ring buffer instance configuration.
  84  *
  85  * Declare as "static const" within the client object to ensure the inline fast
  86  * paths can be optimized.
  87  *
  88  * alloc/sync pairs:
  89  *
  90  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  91  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  92  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  93  *   lib_ring_buffer_put_cpu()).
  94  *
  95  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  96  *   Per-cpu buffer with global synchronization. Tracing can be performed with
  97  *   preemption enabled, statistically stays on the local buffers.
  98  *
  99  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 100  *   Should only be used for buffers belonging to a single thread or protected
 101  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 102  *   should be disabled in this kind of configuration.
 103  *
 104  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 105  *   Global shared buffer with global synchronization.
 106  *
 107  * wakeup:
 108  *
 109  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
 110  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 111  * don't want to call into the wakeup code on the tracing path. Use in
 112  * combination with "read_timer_interval" channel_create() argument.
 113  *
 114  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 115  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 116  * for drivers.
 117  *
 118  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 119  * has the responsibility to perform wakeups.
 120  */
 121 struct lib_ring_buffer_config {
 122         enum {
 123                 RING_BUFFER_ALLOC_PER_CPU,
 124                 RING_BUFFER_ALLOC_GLOBAL,
 125         } alloc;
 126         enum {
 127                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 128                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 129         } sync;
 130         enum {
 131                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 132                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 133         } mode;
 134         enum {
 135                 RING_BUFFER_SPLICE,
 136                 RING_BUFFER_MMAP,
 137                 RING_BUFFER_READ,               /* TODO */
 138                 RING_BUFFER_ITERATOR,
 139                 RING_BUFFER_NONE,
 140         } output;
 141         enum {
 142                 RING_BUFFER_PAGE,
 143                 RING_BUFFER_VMAP,               /* TODO */
 144                 RING_BUFFER_STATIC,             /* TODO */
 145         } backend;
 146         enum {
 147                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 148                 RING_BUFFER_OOPS_CONSISTENCY,
 149         } oops;
 150         enum {
 151                 RING_BUFFER_IPI_BARRIER,
 152                 RING_BUFFER_NO_IPI_BARRIER,
 153         } ipi;
 154         enum {
 155                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 156                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 157                                                  * writer wakes up reader,
 158                                                  * not lock-free
 159                                                  * (takes spinlock).
 160                                                  */
 161         } wakeup;
 162         /*
 163          * tsc_bits: timestamp bits saved at each record.
 164          *   0 and 64 disable the timestamp compression scheme.
 165          */
 166         unsigned int tsc_bits;
 167         struct lib_ring_buffer_client_cb cb;
 168 };
 169
 170 /*
 171  * ring buffer context
 172  *
 173  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 174  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 175  * lib_ring_buffer_write().
 176  */
 177 struct lib_ring_buffer_ctx {
 178         /* input received by lib_ring_buffer_reserve(), saved here. */
 179         struct channel *chan;           /* channel */
 180         void *priv;                     /* client private data */
 181         size_t data_size;               /* size of payload */
 182         int largest_align;              /*
 183                                          * alignment of the largest element
 184                                          * in the payload
 185                                          */
 186         int cpu;                        /* processor id */
 187
 188         /* output from lib_ring_buffer_reserve() */
 189         struct lib_ring_buffer *buf;    /*
 190                                          * buffer corresponding to processor id
 191                                          * for this channel
 192                                          */
 193         size_t slot_size;               /* size of the reserved slot */
 194         unsigned long buf_offset;       /* offset following the record header */
 195         unsigned long pre_offset;       /*
 196                                          * Initial offset position _before_
 197                                          * the record is written. Positioned
 198                                          * prior to record header alignment
 199                                          * padding.
 200                                          */
 201         u64 tsc;                        /* time-stamp counter value */
 202         unsigned int rflags;            /* reservation flags */
 203 };
 204
 205 /**
 206  * lib_ring_buffer_ctx_init - initialize ring buffer context
 207  * @ctx: ring buffer context to initialize
 208  * @chan: channel
 209  * @priv: client private data
 210  * @data_size: size of record data payload. It must be greater than 0.
 211  * @largest_align: largest alignment within data payload types
 212  * @cpu: processor id
 213  */
 214 static inline
 215 void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx *ctx,
 216                               struct channel *chan, void *priv,
 217                               size_t data_size, int largest_align,
 218                               int cpu)
 219 {
 220         ctx->chan = chan;
 221         ctx->priv = priv;
 222         ctx->data_size = data_size;
 223         ctx->largest_align = largest_align;
 224         ctx->cpu = cpu;
 225         ctx->rflags = 0;
 226 }
 227
 228 /*
 229  * Reservation flags.
 230  *
 231  * RING_BUFFER_RFLAG_FULL_TSC
 232  *
 233  * This flag is passed to record_header_size() and to the primitive used to
 234  * write the record header. It indicates that the full 64-bit time value is
 235  * needed in the record header. If this flag is not set, the record header needs
 236  * only to contain "tsc_bits" bit of time value.
 237  *
 238  * Reservation flags can be added by the client, starting from
 239  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 240  * record_header_size() to lib_ring_buffer_write_record_header().
 241  */
 242 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 243 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 244
 245 #ifndef LTTNG_TRACER_CORE_H
 246 #error "lttng-tracer-core.h is needed for RING_BUFFER_ALIGN define"
 247 #endif
 248
 249 /*
 250  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 251  * compile-time. We have to duplicate the "config->align" information and the
 252  * definition here because config->align is used both in the slow and fast
 253  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 254  */
 255 #ifdef RING_BUFFER_ALIGN
 256
 257 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 258
 259 /*
 260  * Calculate the offset needed to align the type.
 261  * size_of_type must be non-zero.
 262  */
 263 static inline
 264 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 265 {
 266         return offset_align(align_drift, size_of_type);
 267 }
 268
 269 #else
 270
 271 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 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 0;
 281 }
 282
 283 #endif
 284
 285 /**
 286  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 287  * @ctx: ring buffer context.
 288  */
 289 static inline
 290 void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx *ctx,
 291                            size_t alignment)
 292 {
 293         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 294                                                  alignment);
 295 }
 296
 297 /*
 298  * lib_ring_buffer_check_config() returns 0 on success.
 299  * Used internally to check for valid configurations at channel creation.
 300  */
 301 static inline
 302 int lib_ring_buffer_check_config(const struct lib_ring_buffer_config *config,
 303                              unsigned int switch_timer_interval,
 304                              unsigned int read_timer_interval)
 305 {
 306         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 307             && config->sync == RING_BUFFER_SYNC_PER_CPU
 308             && switch_timer_interval)
 309                 return -EINVAL;
 310         return 0;
 311 }
 312
 313 #include "../../wrapper/ringbuffer/vatomic.h"
 314
 315 #endif /* _LIB_RING_BUFFER_CONFIG_H */