module/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 #include <sys/zfs_context.h>
  27 #include <sys/spa.h>
  28 #include <sys/vdev_impl.h>
  29 #include <sys/zio.h>
  30 #include <sys/avl.h>
  31
  32 /*
  33  * These tunables are for performance analysis.
  34  */
  35 /*
  36  * zfs_vdev_max_pending is the maximum number of i/os concurrently
  37  * pending to each device.  zfs_vdev_min_pending is the initial number
  38  * of i/os pending to each device (before it starts ramping up to
  39  * max_pending).
  40  */
  41 int zfs_vdev_max_pending = 35;
  42 int zfs_vdev_min_pending = 4;
  43
  44 /* deadline = pri + (lbolt >> time_shift) */
  45 int zfs_vdev_time_shift = 6;
  46
  47 /* exponential I/O issue ramp-up rate */
  48 int zfs_vdev_ramp_rate = 2;
  49
  50 /*
  51  * To reduce IOPs, we aggregate small adjacent i/os into one large i/o.
  52  * For read i/os, we also aggregate across small adjacency gaps.
  53  */
  54 int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
  55 int zfs_vdev_read_gap_limit = 32 << 10;
  56
  57 /*
  58  * Virtual device vector for disk I/O scheduling.
  59  */
  60 int
  61 vdev_queue_deadline_compare(const void *x1, const void *x2)
  62 {
  63         const zio_t *z1 = x1;
  64         const zio_t *z2 = x2;
  65
  66         if (z1->io_deadline < z2->io_deadline)
  67                 return (-1);
  68         if (z1->io_deadline > z2->io_deadline)
  69                 return (1);
  70
  71         if (z1->io_offset < z2->io_offset)
  72                 return (-1);
  73         if (z1->io_offset > z2->io_offset)
  74                 return (1);
  75
  76         if (z1 < z2)
  77                 return (-1);
  78         if (z1 > z2)
  79                 return (1);
  80
  81         return (0);
  82 }
  83
  84 int
  85 vdev_queue_offset_compare(const void *x1, const void *x2)
  86 {
  87         const zio_t *z1 = x1;
  88         const zio_t *z2 = x2;
  89
  90         if (z1->io_offset < z2->io_offset)
  91                 return (-1);
  92         if (z1->io_offset > z2->io_offset)
  93                 return (1);
  94
  95         if (z1 < z2)
  96                 return (-1);
  97         if (z1 > z2)
  98                 return (1);
  99
 100         return (0);
 101 }
 102
 103 void
 104 vdev_queue_init(vdev_t *vd)
 105 {
 106         vdev_queue_t *vq = &vd->vdev_queue;
 107
 108         mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
 109
 110         avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
 111             sizeof (zio_t), offsetof(struct zio, io_deadline_node));
 112
 113         avl_create(&vq->vq_read_tree, vdev_queue_offset_compare,
 114             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 115
 116         avl_create(&vq->vq_write_tree, vdev_queue_offset_compare,
 117             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 118
 119         avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
 120             sizeof (zio_t), offsetof(struct zio, io_offset_node));
 121 }
 122
 123 void
 124 vdev_queue_fini(vdev_t *vd)
 125 {
 126         vdev_queue_t *vq = &vd->vdev_queue;
 127
 128         avl_destroy(&vq->vq_deadline_tree);
 129         avl_destroy(&vq->vq_read_tree);
 130         avl_destroy(&vq->vq_write_tree);
 131         avl_destroy(&vq->vq_pending_tree);
 132
 133         mutex_destroy(&vq->vq_lock);
 134 }
 135
 136 static void
 137 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
 138 {
 139         avl_add(&vq->vq_deadline_tree, zio);
 140         avl_add(zio->io_vdev_tree, zio);
 141 }
 142
 143 static void
 144 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
 145 {
 146         avl_remove(&vq->vq_deadline_tree, zio);
 147         avl_remove(zio->io_vdev_tree, zio);
 148 }
 149
 150 static void
 151 vdev_queue_agg_io_done(zio_t *aio)
 152 {
 153         zio_t *pio;
 154
 155         while ((pio = zio_walk_parents(aio)) != NULL)
 156                 if (aio->io_type == ZIO_TYPE_READ)
 157                         bcopy((char *)aio->io_data + (pio->io_offset -
 158                             aio->io_offset), pio->io_data, pio->io_size);
 159
 160         zio_buf_free(aio->io_data, aio->io_size);
 161 }
 162
 163 /*
 164  * Compute the range spanned by two i/os, which is the endpoint of the last
 165  * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
 166  * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
 167  * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
 168  */
 169 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
 170 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
 171
 172 static zio_t *
 173 vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 174 {
 175         zio_t *fio, *lio, *aio, *dio, *nio;
 176         avl_tree_t *t;
 177         int flags;
 178         uint64_t maxspan = zfs_vdev_aggregation_limit;
 179         uint64_t maxgap;
 180
 181         ASSERT(MUTEX_HELD(&vq->vq_lock));
 182
 183         if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
 184             avl_numnodes(&vq->vq_deadline_tree) == 0)
 185                 return (NULL);
 186
 187         fio = lio = avl_first(&vq->vq_deadline_tree);
 188
 189         t = fio->io_vdev_tree;
 190         flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
 191         maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0;
 192
 193         if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
 194                 /*
 195                  * We can aggregate I/Os that are adjacent and of the
 196                  * same flavor, as expressed by the AGG_INHERIT flags.
 197                  * The latter is necessary so that certain attributes
 198                  * of the I/O, such as whether it's a normal I/O or a
 199                  * scrub/resilver, can be preserved in the aggregate.
 200                  */
 201                 while ((dio = AVL_PREV(t, fio)) != NULL &&
 202                     (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
 203                     IO_SPAN(dio, lio) <= maxspan && IO_GAP(dio, fio) <= maxgap)
 204                         fio = dio;
 205
 206                 while ((dio = AVL_NEXT(t, lio)) != NULL &&
 207                     (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
 208                     IO_SPAN(fio, dio) <= maxspan && IO_GAP(lio, dio) <= maxgap)
 209                         lio = dio;
 210         }
 211
 212         if (fio != lio) {
 213                 uint64_t size = IO_SPAN(fio, lio);
 214                 ASSERT(size <= zfs_vdev_aggregation_limit);
 215
 216                 aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
 217                     zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_NOW,
 218                     flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
 219                     vdev_queue_agg_io_done, NULL);
 220
 221                 nio = fio;
 222                 do {
 223                         dio = nio;
 224                         nio = AVL_NEXT(t, dio);
 225                         ASSERT(dio->io_type == aio->io_type);
 226                         ASSERT(dio->io_vdev_tree == t);
 227
 228                         if (dio->io_type == ZIO_TYPE_WRITE)
 229                                 bcopy(dio->io_data, (char *)aio->io_data +
 230                                     (dio->io_offset - aio->io_offset),
 231                                     dio->io_size);
 232
 233                         zio_add_child(dio, aio);
 234                         vdev_queue_io_remove(vq, dio);
 235                         zio_vdev_io_bypass(dio);
 236                         zio_execute(dio);
 237                 } while (dio != lio);
 238
 239                 avl_add(&vq->vq_pending_tree, aio);
 240
 241                 return (aio);
 242         }
 243
 244         ASSERT(fio->io_vdev_tree == t);
 245         vdev_queue_io_remove(vq, fio);
 246
 247         avl_add(&vq->vq_pending_tree, fio);
 248
 249         return (fio);
 250 }
 251
 252 zio_t *
 253 vdev_queue_io(zio_t *zio)
 254 {
 255         vdev_queue_t *vq = &zio->io_vd->vdev_queue;
 256         zio_t *nio;
 257
 258         ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);
 259
 260         if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
 261                 return (zio);
 262
 263         zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
 264
 265         if (zio->io_type == ZIO_TYPE_READ)
 266                 zio->io_vdev_tree = &vq->vq_read_tree;
 267         else
 268                 zio->io_vdev_tree = &vq->vq_write_tree;
 269
 270         mutex_enter(&vq->vq_lock);
 271
 272         zio->io_deadline = (lbolt64 >> zfs_vdev_time_shift) + zio->io_priority;
 273
 274         vdev_queue_io_add(vq, zio);
 275
 276         nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending);
 277
 278         mutex_exit(&vq->vq_lock);
 279
 280         if (nio == NULL)
 281                 return (NULL);
 282
 283         if (nio->io_done == vdev_queue_agg_io_done) {
 284                 zio_nowait(nio);
 285                 return (NULL);
 286         }
 287
 288         return (nio);
 289 }
 290
 291 void
 292 vdev_queue_io_done(zio_t *zio)
 293 {
 294         vdev_queue_t *vq = &zio->io_vd->vdev_queue;
 295
 296         mutex_enter(&vq->vq_lock);
 297
 298         avl_remove(&vq->vq_pending_tree, zio);
 299
 300         for (int i = 0; i < zfs_vdev_ramp_rate; i++) {
 301                 zio_t *nio = vdev_queue_io_to_issue(vq, zfs_vdev_max_pending);
 302                 if (nio == NULL)
 303                         break;
 304                 mutex_exit(&vq->vq_lock);
 305                 if (nio->io_done == vdev_queue_agg_io_done) {
 306                         zio_nowait(nio);
 307                 } else {
 308                         zio_vdev_io_reissue(nio);
 309                         zio_execute(nio);
 310                 }
 311                 mutex_enter(&vq->vq_lock);
 312         }
 313
 314         mutex_exit(&vq->vq_lock);
 315 }