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 <lib/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                                       void *client_ctx);
  53
  54         /* Slow path only, at subbuffer switch */
  55         size_t (*subbuffer_header_size) (void);
  56         void (*buffer_begin) (struct lib_ring_buffer *buf, u64 tsc,
  57                               unsigned int subbuf_idx);
  58         void (*buffer_end) (struct lib_ring_buffer *buf, u64 tsc,
  59                             unsigned int subbuf_idx, unsigned long data_size);
  60
  61         /* Optional callbacks (can be set to NULL) */
  62
  63         /* Called at buffer creation/finalize */
  64         int (*buffer_create) (struct lib_ring_buffer *buf, void *priv,
  65                               int cpu, const char *name);
  66         /*
  67          * Clients should guarantee that no new reader handle can be opened
  68          * after finalize.
  69          */
  70         void (*buffer_finalize) (struct lib_ring_buffer *buf, void *priv, int cpu);
  71
  72         /*
  73          * Extract header length, payload length and timestamp from event
  74          * record. Used by buffer iterators. Timestamp is only used by channel
  75          * iterator.
  76          */
  77         void (*record_get) (const struct lib_ring_buffer_config *config,
  78                             struct channel *chan, struct lib_ring_buffer *buf,
  79                             size_t offset, size_t *header_len,
  80                             size_t *payload_len, u64 *timestamp);
  81 };
  82
  83 /*
  84  * Ring buffer instance configuration.
  85  *
  86  * Declare as "static const" within the client object to ensure the inline fast
  87  * paths can be optimized.
  88  *
  89  * alloc/sync pairs:
  90  *
  91  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU :
  92  *   Per-cpu buffers with per-cpu synchronization. Tracing must be performed
  93  *   with preemption disabled (lib_ring_buffer_get_cpu() and
  94  *   lib_ring_buffer_put_cpu()).
  95  *
  96  * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL :
  97  *   Per-cpu buffer with global synchronization. Tracing can be performed with
  98  *   preemption enabled, statistically stays on the local buffers.
  99  *
 100  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU :
 101  *   Should only be used for buffers belonging to a single thread or protected
 102  *   by mutual exclusion by the client. Note that periodical sub-buffer switch
 103  *   should be disabled in this kind of configuration.
 104  *
 105  * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL :
 106  *   Global shared buffer with global synchronization.
 107  *
 108  * wakeup:
 109  *
 110  * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the
 111  * buffers and wake up readers if data is ready. Mainly useful for tracers which
 112  * don't want to call into the wakeup code on the tracing path. Use in
 113  * combination with "read_timer_interval" channel_create() argument.
 114  *
 115  * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is
 116  * ready to read. Lower latencies before the reader is woken up. Mainly suitable
 117  * for drivers.
 118  *
 119  * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client
 120  * has the responsibility to perform wakeups.
 121  */
 122 struct lib_ring_buffer_config {
 123         enum {
 124                 RING_BUFFER_ALLOC_PER_CPU,
 125                 RING_BUFFER_ALLOC_GLOBAL,
 126         } alloc;
 127         enum {
 128                 RING_BUFFER_SYNC_PER_CPU,       /* Wait-free */
 129                 RING_BUFFER_SYNC_GLOBAL,        /* Lock-free */
 130         } sync;
 131         enum {
 132                 RING_BUFFER_OVERWRITE,          /* Overwrite when buffer full */
 133                 RING_BUFFER_DISCARD,            /* Discard when buffer full */
 134         } mode;
 135         enum {
 136                 RING_BUFFER_SPLICE,
 137                 RING_BUFFER_MMAP,
 138                 RING_BUFFER_READ,               /* TODO */
 139                 RING_BUFFER_ITERATOR,
 140                 RING_BUFFER_NONE,
 141         } output;
 142         enum {
 143                 RING_BUFFER_PAGE,
 144                 RING_BUFFER_VMAP,               /* TODO */
 145                 RING_BUFFER_STATIC,             /* TODO */
 146         } backend;
 147         enum {
 148                 RING_BUFFER_NO_OOPS_CONSISTENCY,
 149                 RING_BUFFER_OOPS_CONSISTENCY,
 150         } oops;
 151         enum {
 152                 RING_BUFFER_IPI_BARRIER,
 153                 RING_BUFFER_NO_IPI_BARRIER,
 154         } ipi;
 155         enum {
 156                 RING_BUFFER_WAKEUP_BY_TIMER,    /* wake up performed by timer */
 157                 RING_BUFFER_WAKEUP_BY_WRITER,   /*
 158                                                  * writer wakes up reader,
 159                                                  * not lock-free
 160                                                  * (takes spinlock).
 161                                                  */
 162         } wakeup;
 163         /*
 164          * tsc_bits: timestamp bits saved at each record.
 165          *   0 and 64 disable the timestamp compression scheme.
 166          */
 167         unsigned int tsc_bits;
 168         struct lib_ring_buffer_client_cb cb;
 169 };
 170
 171 /*
 172  * ring buffer context
 173  *
 174  * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(),
 175  * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and
 176  * lib_ring_buffer_write().
 177  */
 178 struct lib_ring_buffer_ctx {
 179         /* input received by lib_ring_buffer_reserve(), saved here. */
 180         struct channel *chan;           /* channel */
 181         void *priv;                     /* client private data */
 182         size_t data_size;               /* size of payload */
 183         int largest_align;              /*
 184                                          * alignment of the largest element
 185                                          * in the payload
 186                                          */
 187         int cpu;                        /* processor id */
 188
 189         /* output from lib_ring_buffer_reserve() */
 190         struct lib_ring_buffer *buf;    /*
 191                                          * buffer corresponding to processor id
 192                                          * for this channel
 193                                          */
 194         size_t slot_size;               /* size of the reserved slot */
 195         unsigned long buf_offset;       /* offset following the record header */
 196         unsigned long pre_offset;       /*
 197                                          * Initial offset position _before_
 198                                          * the record is written. Positioned
 199                                          * prior to record header alignment
 200                                          * padding.
 201                                          */
 202         u64 tsc;                        /* time-stamp counter value */
 203         unsigned int rflags;            /* reservation flags */
 204         /* Cache backend pages pointer chasing. */
 205         struct lib_ring_buffer_backend_pages *backend_pages;
 206 };
 207
 208 /**
 209  * lib_ring_buffer_ctx_init - initialize ring buffer context
 210  * @ctx: ring buffer context to initialize
 211  * @chan: channel
 212  * @priv: client private data
 213  * @data_size: size of record data payload. It must be greater than 0.
 214  * @largest_align: largest alignment within data payload types
 215  * @cpu: processor id
 216  */
 217 static inline
 218 void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx *ctx,
 219                               struct channel *chan, void *priv,
 220                               size_t data_size, int largest_align,
 221                               int cpu)
 222 {
 223         ctx->chan = chan;
 224         ctx->priv = priv;
 225         ctx->data_size = data_size;
 226         ctx->largest_align = largest_align;
 227         ctx->cpu = cpu;
 228         ctx->rflags = 0;
 229         ctx->backend_pages = NULL;
 230 }
 231
 232 /*
 233  * Reservation flags.
 234  *
 235  * RING_BUFFER_RFLAG_FULL_TSC
 236  *
 237  * This flag is passed to record_header_size() and to the primitive used to
 238  * write the record header. It indicates that the full 64-bit time value is
 239  * needed in the record header. If this flag is not set, the record header needs
 240  * only to contain "tsc_bits" bit of time value.
 241  *
 242  * Reservation flags can be added by the client, starting from
 243  * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from
 244  * record_header_size() to lib_ring_buffer_write_record_header().
 245  */
 246 #define RING_BUFFER_RFLAG_FULL_TSC              (1U << 0)
 247 #define RING_BUFFER_RFLAG_END                   (1U << 1)
 248
 249 #ifndef LTTNG_TRACER_CORE_H
 250 #error "lttng-tracer-core.h is needed for RING_BUFFER_ALIGN define"
 251 #endif
 252
 253 /*
 254  * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at
 255  * compile-time. We have to duplicate the "config->align" information and the
 256  * definition here because config->align is used both in the slow and fast
 257  * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code.
 258  */
 259 #ifdef RING_BUFFER_ALIGN
 260
 261 # define RING_BUFFER_ALIGN_ATTR         /* Default arch alignment */
 262
 263 /*
 264  * Calculate the offset needed to align the type.
 265  * size_of_type must be non-zero.
 266  */
 267 static inline
 268 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 269 {
 270         return offset_align(align_drift, size_of_type);
 271 }
 272
 273 #else
 274
 275 # define RING_BUFFER_ALIGN_ATTR __attribute__((packed))
 276
 277 /*
 278  * Calculate the offset needed to align the type.
 279  * size_of_type must be non-zero.
 280  */
 281 static inline
 282 unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type)
 283 {
 284         return 0;
 285 }
 286
 287 #endif
 288
 289 /**
 290  * lib_ring_buffer_align_ctx - Align context offset on "alignment"
 291  * @ctx: ring buffer context.
 292  */
 293 static inline
 294 void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx *ctx,
 295                            size_t alignment)
 296 {
 297         ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset,
 298                                                  alignment);
 299 }
 300
 301 /*
 302  * lib_ring_buffer_check_config() returns 0 on success.
 303  * Used internally to check for valid configurations at channel creation.
 304  */
 305 static inline
 306 int lib_ring_buffer_check_config(const struct lib_ring_buffer_config *config,
 307                              unsigned int switch_timer_interval,
 308                              unsigned int read_timer_interval)
 309 {
 310         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL
 311             && config->sync == RING_BUFFER_SYNC_PER_CPU
 312             && switch_timer_interval)
 313                 return -EINVAL;
 314         return 0;
 315 }
 316
 317 #include <wrapper/ringbuffer/vatomic.h>
 318
 319 #endif /* _LIB_RING_BUFFER_CONFIG_H */