usr/src/uts/common/fs/zfs/vdev_queue.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26 /*
  27  * Copyright (c) 2012 by Delphix. All rights reserved.
  28  */
  29
  30 #include <sys/zfs_context.h>
  31 #include <sys/vdev_impl.h>
  32 #include <sys/zio.h>
  33 #include <sys/avl.h>
  34
  35 /*
  36  * These tunables are for performance analysis.
  37  */
  38 /*
  39  * zfs_vdev_max_pending is the maximum number of i/os concurrently
  40  * pending to each device.  zfs_vdev_min_pending is the initial number
  41  * of i/os pending to each device (before it starts ramping up to
  42  * max_pending).
  43  */
  44 int zfs_vdev_max_pending = 10;
  45 int zfs_vdev_min_pending = 4;
  46
  47 /* deadline = pri + ddi_get_lbolt64() >> time_shift) */
  48 int zfs_vdev_time_shift = 6;
  49
  50 /* exponential I/O issue ramp-up rate */
  51 int zfs_vdev_ramp_rate = 2;
  52
  53 /*
  54  * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
  55  * For read I/Os, we also aggregate across small adjacency gaps; for writes
  56  * we include spans of optional I/Os to aid aggregation at the disk even when
  57  * they aren't able to help us aggregate at this level.
  58  */
  59 int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
  60 int zfs_vdev_read_gap_limit = 32 << 10;
  61 int zfs_vdev_write_gap_limit = 4 << 10;
  62
  63 /*
  64  * Virtual device vector for disk I/O scheduling.
  65  */
  66 int
  67 vdev_queue_deadline_compare(const void *x1, const void *x2)
  68 {
  69         const zio_t *z1 = x1;
  70         const zio_t *z2 = x2;
  71
  72         if (z1->io_deadline < z2->io_deadline)
  73                 return (-1);
  74         if (z1->io_deadline > z2->io_deadline)
  75                 return (1);
  76
  77         if (z1->io_offset < z2->io_offset)
  78                 return (-1);
  79         if (z1->io_offset > z2->io_offset)
  80                 return (1);
  81
  82         if (z1 < z2)
  83                 return (-1);
  84         if (z1 > z2)
  85                 return (1);
  86
  87         return (0);
  88 }
  89
  90 int
  91 vdev_queue_offset_compare(const void *x1, const void *x2)
  92 {
  93         const zio_t *z1 = x1;
  94         const zio_t *z2 = x2;
  95
  96         if (z1->io_offset < z2->io_offset)
  97                 return (-1);
  98         if (z1->io_offset > z2->io_offset)
  99                 return (1);
 100
 101         if (z1 < z2)
 102                 return (-1);
 103         if (z1 > z2)
 104                 return (1);
 105
 106         return (0);
 107 }
 108
 109 void
 110 vdev_queue_init(vdev_t *vd)
 111 {
 112         vdev_queue_t *vq = &vd->vdev_queue;
 113
 114         mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
 115
 116         avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
 117             sizeof (zio_t), offsetof(struct zio, io_deadline_node));
 118
 119         avl_create(&vq->vq_read_tree, vdev_queue_offset_compare,
 120             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 121
 122         avl_create(&vq->vq_write_tree, vdev_queue_offset_compare,
 123             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 124
 125         avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
 126             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 127 }
 128
 129 void
 130 vdev_queue_fini(vdev_t *vd)
 131 {
 132         vdev_queue_t *vq = &vd->vdev_queue;
 133
 134         avl_destroy(&vq->vq_deadline_tree);
 135         avl_destroy(&vq->vq_read_tree);
 136         avl_destroy(&vq->vq_write_tree);
 137         avl_destroy(&vq->vq_pending_tree);
 138
 139         mutex_destroy(&vq->vq_lock);
 140 }
 141
 142 static void
 143 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
 144 {
 145         avl_add(&vq->vq_deadline_tree, zio);
 146         avl_add(zio->io_vdev_tree, zio);
 147 }
 148
 149 static void
 150 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
 151 {
 152         avl_remove(&vq->vq_deadline_tree, zio);
 153         avl_remove(zio->io_vdev_tree, zio);
 154 }
 155
 156 static void
 157 vdev_queue_agg_io_done(zio_t *aio)
 158 {
 159         zio_t *pio;
 160
 161         while ((pio = zio_walk_parents(aio)) != NULL)
 162                 if (aio->io_type == ZIO_TYPE_READ)
 163                         bcopy((char *)aio->io_data + (pio->io_offset -
 164                             aio->io_offset), pio->io_data, pio->io_size);
 165
 166         zio_buf_free(aio->io_data, aio->io_size);
 167 }
 168
 169 /*
 170  * Compute the range spanned by two i/os, which is the endpoint of the last
 171  * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
 172  * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
 173  * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
 174  */
 175 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
 176 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
 177
 178 static zio_t *
 179 vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 180 {
 181         zio_t *fio, *lio, *aio, *dio, *nio, *mio;
 182         avl_tree_t *t;
 183         int flags;
 184         uint64_t maxspan = zfs_vdev_aggregation_limit;
 185         uint64_t maxgap;
 186         int stretch;
 187
 188 again:
 189         ASSERT(MUTEX_HELD(&vq->vq_lock));
 190
 191         if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
 192             avl_numnodes(&vq->vq_deadline_tree) == 0)
 193                 return (NULL);
 194
 195         fio = lio = avl_first(&vq->vq_deadline_tree);
 196
 197         t = fio->io_vdev_tree;
 198         flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
 199         maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0;
 200
 201         if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
 202                 /*
 203                  * We can aggregate I/Os that are sufficiently adjacent and of
 204                  * the same flavor, as expressed by the AGG_INHERIT flags.
 205                  * The latter requirement is necessary so that certain
 206                  * attributes of the I/O, such as whether it's a normal I/O
 207                  * or a scrub/resilver, can be preserved in the aggregate.
 208                  * We can include optional I/Os, but don't allow them
 209                  * to begin a range as they add no benefit in that situation.
 210                  */
 211
 212                 /*
 213                  * We keep track of the last non-optional I/O.
 214                  */
 215                 mio = (fio->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : fio;
 216
 217                 /*
 218                  * Walk backwards through sufficiently contiguous I/Os
 219                  * recording the last non-option I/O.
 220                  */
 221                 while ((dio = AVL_PREV(t, fio)) != NULL &&
 222                     (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
 223                     IO_SPAN(dio, lio) <= maxspan &&
 224                     IO_GAP(dio, fio) <= maxgap) {
 225                         fio = dio;
 226                         if (mio == NULL && !(fio->io_flags & ZIO_FLAG_OPTIONAL))
 227                                 mio = fio;
 228                 }
 229
 230                 /*
 231                  * Skip any initial optional I/Os.
 232                  */
 233                 while ((fio->io_flags & ZIO_FLAG_OPTIONAL) && fio != lio) {
 234                         fio = AVL_NEXT(t, fio);
 235                         ASSERT(fio != NULL);
 236                 }
 237
 238                 /*
 239                  * Walk forward through sufficiently contiguous I/Os.
 240                  */
 241                 while ((dio = AVL_NEXT(t, lio)) != NULL &&
 242                     (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
 243                     IO_SPAN(fio, dio) <= maxspan &&
 244                     IO_GAP(lio, dio) <= maxgap) {
 245                         lio = dio;
 246                         if (!(lio->io_flags & ZIO_FLAG_OPTIONAL))
 247                                 mio = lio;
 248                 }
 249
 250                 /*
 251                  * Now that we've established the range of the I/O aggregation
 252                  * we must decide what to do with trailing optional I/Os.
 253                  * For reads, there's nothing to do. While we are unable to
 254                  * aggregate further, it's possible that a trailing optional
 255                  * I/O would allow the underlying device to aggregate with
 256                  * subsequent I/Os. We must therefore determine if the next
 257                  * non-optional I/O is close enough to make aggregation
 258                  * worthwhile.
 259                  */
 260                 stretch = B_FALSE;
 261                 if (t != &vq->vq_read_tree && mio != NULL) {
 262                         nio = lio;
 263                         while ((dio = AVL_NEXT(t, nio)) != NULL &&
 264                             IO_GAP(nio, dio) == 0 &&
 265                             IO_GAP(mio, dio) <= zfs_vdev_write_gap_limit) {
 266                                 nio = dio;
 267                                 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
 268                                         stretch = B_TRUE;
 269                                         break;
 270                                 }
 271                         }
 272                 }
 273
 274                 if (stretch) {
 275                         /* This may be a no-op. */
 276                         VERIFY((dio = AVL_NEXT(t, lio)) != NULL);
 277                         dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
 278                 } else {
 279                         while (lio != mio && lio != fio) {
 280                                 ASSERT(lio->io_flags & ZIO_FLAG_OPTIONAL);
 281                                 lio = AVL_PREV(t, lio);
 282                                 ASSERT(lio != NULL);
 283                         }
 284                 }
 285         }
 286
 287         if (fio != lio) {
 288                 uint64_t size = IO_SPAN(fio, lio);
 289                 ASSERT(size <= zfs_vdev_aggregation_limit);
 290
 291                 aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
 292                     zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_AGG,
 293                     flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
 294                     vdev_queue_agg_io_done, NULL);
 295                 aio->io_timestamp = fio->io_timestamp;
 296
 297                 nio = fio;
 298                 do {
 299                         dio = nio;
 300                         nio = AVL_NEXT(t, dio);
 301                         ASSERT(dio->io_type == aio->io_type);
 302                         ASSERT(dio->io_vdev_tree == t);
 303
 304                         if (dio->io_flags & ZIO_FLAG_NODATA) {
 305                                 ASSERT(dio->io_type == ZIO_TYPE_WRITE);
 306                                 bzero((char *)aio->io_data + (dio->io_offset -
 307                                     aio->io_offset), dio->io_size);
 308                         } else if (dio->io_type == ZIO_TYPE_WRITE) {
 309                                 bcopy(dio->io_data, (char *)aio->io_data +
 310                                     (dio->io_offset - aio->io_offset),
 311                                     dio->io_size);
 312                         }
 313
 314                         zio_add_child(dio, aio);
 315                         vdev_queue_io_remove(vq, dio);
 316                         zio_vdev_io_bypass(dio);
 317                         zio_execute(dio);
 318                 } while (dio != lio);
 319
 320                 avl_add(&vq->vq_pending_tree, aio);
 321
 322                 return (aio);
 323         }
 324
 325         ASSERT(fio->io_vdev_tree == t);
 326         vdev_queue_io_remove(vq, fio);
 327
 328         /*
 329          * If the I/O is or was optional and therefore has no data, we need to
 330          * simply discard it. We need to drop the vdev queue's lock to avoid a
 331          * deadlock that we could encounter since this I/O will complete
 332          * immediately.
 333          */
 334         if (fio->io_flags & ZIO_FLAG_NODATA) {
 335                 mutex_exit(&vq->vq_lock);
 336                 zio_vdev_io_bypass(fio);
 337                 zio_execute(fio);
 338                 mutex_enter(&vq->vq_lock);
 339                 goto again;
 340         }
 341
 342         avl_add(&vq->vq_pending_tree, fio);
 343
 344         return (fio);
 345 }
 346
 347 zio_t *
 348 vdev_queue_io(zio_t *zio)
 349 {
 350         vdev_queue_t *vq = &zio->io_vd->vdev_queue;
 351         zio_t *nio;
 352
 353         ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);
 354
 355         if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
 356                 return (zio);
 357
 358         zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
 359
 360         if (zio->io_type == ZIO_TYPE_READ)
 361                 zio->io_vdev_tree = &vq->vq_read_tree;
 362         else
 363                 zio->io_vdev_tree = &vq->vq_write_tree;
 364
 365         mutex_enter(&vq->vq_lock);
 366
 367         zio->io_timestamp = ddi_get_lbolt64();
 368         zio->io_deadline = (zio->io_timestamp >> zfs_vdev_time_shift) +
 369             zio->io_priority;
 370
 371         vdev_queue_io_add(vq, zio);
 372
 373         nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending);
 374
 375         mutex_exit(&vq->vq_lock);
 376
 377         if (nio == NULL)
 378                 return (NULL);
 379
 380         if (nio->io_done == vdev_queue_agg_io_done) {
 381                 zio_nowait(nio);
 382                 return (NULL);
 383         }
 384
 385         return (nio);
 386 }
 387
 388 void
 389 vdev_queue_io_done(zio_t *zio)
 390 {
 391         vdev_queue_t *vq = &zio->io_vd->vdev_queue;
 392
 393         if (zio_injection_enabled)
 394                 delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
 395
 396         mutex_enter(&vq->vq_lock);
 397
 398         avl_remove(&vq->vq_pending_tree, zio);
 399
 400         vq->vq_io_complete_ts = ddi_get_lbolt64();
 401         vq->vq_io_delta_ts = vq->vq_io_complete_ts - zio->io_timestamp;
 402
 403         for (int i = 0; i < zfs_vdev_ramp_rate; i++) {
 404                 zio_t *nio = vdev_queue_io_to_issue(vq, zfs_vdev_max_pending);
 405                 if (nio == NULL)
 406                         break;
 407                 mutex_exit(&vq->vq_lock);
 408                 if (nio->io_done == vdev_queue_agg_io_done) {
 409                         zio_nowait(nio);
 410                 } else {
 411                         zio_vdev_io_reissue(nio);
 412                         zio_execute(nio);
 413                 }
 414                 mutex_enter(&vq->vq_lock);
 415         }
 416
 417         mutex_exit(&vq->vq_lock);
 418 }