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_impl.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 = 10; 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; for writes 53 * we include spans of optional I/Os to aid aggregation at the disk even when 54 * they aren't able to help us aggregate at this level. 55 */ 56 int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE; 57 int zfs_vdev_read_gap_limit = 32 << 10; 58 int zfs_vdev_write_gap_limit = 4 << 10; 59 60 /* 61 * Virtual device vector for disk I/O scheduling. 62 */ 63 int 64 vdev_queue_deadline_compare(const void *x1, const void *x2) 65 { 66 const zio_t *z1 = x1; 67 const zio_t *z2 = x2; 68 69 if (z1->io_deadline < z2->io_deadline) 70 return (-1); 71 if (z1->io_deadline > z2->io_deadline) 72 return (1); 73 74 if (z1->io_offset < z2->io_offset) 75 return (-1); 76 if (z1->io_offset > z2->io_offset) 77 return (1); 78 79 if (z1 < z2) 80 return (-1); 81 if (z1 > z2) 82 return (1); 83 84 return (0); 85 } 86 87 int 88 vdev_queue_offset_compare(const void *x1, const void *x2) 89 { 90 const zio_t *z1 = x1; 91 const zio_t *z2 = x2; 92 93 if (z1->io_offset < z2->io_offset) 94 return (-1); 95 if (z1->io_offset > z2->io_offset) 96 return (1); 97 98 if (z1 < z2) 99 return (-1); 100 if (z1 > z2) 101 return (1); 102 103 return (0); 104 } 105 106 void 107 vdev_queue_init(vdev_t *vd) 108 { 109 vdev_queue_t *vq = &vd->vdev_queue; 110 111 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL); 112 113 avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare, 114 sizeof (zio_t), offsetof(struct zio, io_deadline_node)); 115 116 avl_create(&vq->vq_read_tree, vdev_queue_offset_compare, 117 sizeof (zio_t), offsetof(struct zio, io_offset_node)); 118 119 avl_create(&vq->vq_write_tree, vdev_queue_offset_compare, 120 sizeof (zio_t), offsetof(struct zio, io_offset_node)); 121 122 avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare, 123 sizeof (zio_t), offsetof(struct zio, io_offset_node)); 124 } 125 126 void 127 vdev_queue_fini(vdev_t *vd) 128 { 129 vdev_queue_t *vq = &vd->vdev_queue; 130 131 avl_destroy(&vq->vq_deadline_tree); 132 avl_destroy(&vq->vq_read_tree); 133 avl_destroy(&vq->vq_write_tree); 134 avl_destroy(&vq->vq_pending_tree); 135 136 mutex_destroy(&vq->vq_lock); 137 } 138 139 static void 140 vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio) 141 { 142 avl_add(&vq->vq_deadline_tree, zio); 143 avl_add(zio->io_vdev_tree, zio); 144 } 145 146 static void 147 vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio) 148 { 149 avl_remove(&vq->vq_deadline_tree, zio); 150 avl_remove(zio->io_vdev_tree, zio); 151 } 152 153 static void 154 vdev_queue_agg_io_done(zio_t *aio) 155 { 156 zio_t *pio; 157 158 while ((pio = zio_walk_parents(aio)) != NULL) 159 if (aio->io_type == ZIO_TYPE_READ) 160 bcopy((char *)aio->io_data + (pio->io_offset - 161 aio->io_offset), pio->io_data, pio->io_size); 162 163 zio_buf_free(aio->io_data, aio->io_size); 164 } 165 166 /* 167 * Compute the range spanned by two i/os, which is the endpoint of the last 168 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset). 169 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio); 170 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0. 171 */ 172 #define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset) 173 #define IO_GAP(fio, lio) (-IO_SPAN(lio, fio)) 174 175 static zio_t * 176 vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit) 177 { 178 zio_t *fio, *lio, *aio, *dio, *nio, *mio; 179 avl_tree_t *t; 180 int flags; 181 uint64_t maxspan = zfs_vdev_aggregation_limit; 182 uint64_t maxgap; 183 int stretch; 184 185 again: 186 ASSERT(MUTEX_HELD(&vq->vq_lock)); 187 188 if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit || 189 avl_numnodes(&vq->vq_deadline_tree) == 0) 190 return (NULL); 191 192 fio = lio = avl_first(&vq->vq_deadline_tree); 193 194 t = fio->io_vdev_tree; 195 flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT; 196 maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0; 197 198 if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) { 199 /* 200 * We can aggregate I/Os that are sufficiently adjacent and of 201 * the same flavor, as expressed by the AGG_INHERIT flags. 202 * The latter requirement is necessary so that certain 203 * attributes of the I/O, such as whether it's a normal I/O 204 * or a scrub/resilver, can be preserved in the aggregate. 205 * We can include optional I/Os, but don't allow them 206 * to begin a range as they add no benefit in that situation. 207 */ 208 209 /* 210 * We keep track of the last non-optional I/O. 211 */ 212 mio = (fio->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : fio; 213 214 /* 215 * Walk backwards through sufficiently contiguous I/Os 216 * recording the last non-option I/O. 217 */ 218 while ((dio = AVL_PREV(t, fio)) != NULL && 219 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 220 IO_SPAN(dio, lio) <= maxspan && 221 IO_GAP(dio, fio) <= maxgap) { 222 fio = dio; 223 if (mio == NULL && !(fio->io_flags & ZIO_FLAG_OPTIONAL)) 224 mio = fio; 225 } 226 227 /* 228 * Skip any initial optional I/Os. 229 */ 230 while ((fio->io_flags & ZIO_FLAG_OPTIONAL) && fio != lio) { 231 fio = AVL_NEXT(t, fio); 232 ASSERT(fio != NULL); 233 } 234 235 /* 236 * Walk forward through sufficiently contiguous I/Os. 237 */ 238 while ((dio = AVL_NEXT(t, lio)) != NULL && 239 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags && 240 IO_SPAN(fio, dio) <= maxspan && 241 IO_GAP(lio, dio) <= maxgap) { 242 lio = dio; 243 if (!(lio->io_flags & ZIO_FLAG_OPTIONAL)) 244 mio = lio; 245 } 246 247 /* 248 * Now that we've established the range of the I/O aggregation 249 * we must decide what to do with trailing optional I/Os. 250 * For reads, there's nothing to do. While we are unable to 251 * aggregate further, it's possible that a trailing optional 252 * I/O would allow the underlying device to aggregate with 253 * subsequent I/Os. We must therefore determine if the next 254 * non-optional I/O is close enough to make aggregation 255 * worthwhile. 256 */ 257 stretch = B_FALSE; 258 if (t != &vq->vq_read_tree && mio != NULL) { 259 nio = lio; 260 while ((dio = AVL_NEXT(t, nio)) != NULL && 261 IO_GAP(nio, dio) == 0 && 262 IO_GAP(mio, dio) <= zfs_vdev_write_gap_limit) { 263 nio = dio; 264 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) { 265 stretch = B_TRUE; 266 break; 267 } 268 } 269 } 270 271 if (stretch) { 272 /* This may be a no-op. */ 273 VERIFY((dio = AVL_NEXT(t, lio)) != NULL); 274 dio->io_flags &= ~ZIO_FLAG_OPTIONAL; 275 } else { 276 while (lio != mio && lio != fio) { 277 ASSERT(lio->io_flags & ZIO_FLAG_OPTIONAL); 278 lio = AVL_PREV(t, lio); 279 ASSERT(lio != NULL); 280 } 281 } 282 } 283 284 if (fio != lio) { 285 uint64_t size = IO_SPAN(fio, lio); 286 ASSERT(size <= zfs_vdev_aggregation_limit); 287 288 aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset, 289 zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_NOW, 290 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE, 291 vdev_queue_agg_io_done, NULL); 292 293 nio = fio; 294 do { 295 dio = nio; 296 nio = AVL_NEXT(t, dio); 297 ASSERT(dio->io_type == aio->io_type); 298 ASSERT(dio->io_vdev_tree == t); 299 300 if (dio->io_flags & ZIO_FLAG_NODATA) { 301 ASSERT(dio->io_type == ZIO_TYPE_WRITE); 302 bzero((char *)aio->io_data + (dio->io_offset - 303 aio->io_offset), dio->io_size); 304 } else if (dio->io_type == ZIO_TYPE_WRITE) { 305 bcopy(dio->io_data, (char *)aio->io_data + 306 (dio->io_offset - aio->io_offset), 307 dio->io_size); 308 } 309 310 zio_add_child(dio, aio); 311 vdev_queue_io_remove(vq, dio); 312 zio_vdev_io_bypass(dio); 313 zio_execute(dio); 314 } while (dio != lio); 315 316 avl_add(&vq->vq_pending_tree, aio); 317 318 return (aio); 319 } 320 321 ASSERT(fio->io_vdev_tree == t); 322 vdev_queue_io_remove(vq, fio); 323 324 /* 325 * If the I/O is or was optional and therefore has no data, we need to 326 * simply discard it. We need to drop the vdev queue's lock to avoid a 327 * deadlock that we could encounter since this I/O will complete 328 * immediately. 329 */ 330 if (fio->io_flags & ZIO_FLAG_NODATA) { 331 mutex_exit(&vq->vq_lock); 332 zio_vdev_io_bypass(fio); 333 zio_execute(fio); 334 mutex_enter(&vq->vq_lock); 335 goto again; 336 } 337 338 avl_add(&vq->vq_pending_tree, fio); 339 340 return (fio); 341 } 342 343 zio_t * 344 vdev_queue_io(zio_t *zio) 345 { 346 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 347 zio_t *nio; 348 349 ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE); 350 351 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE) 352 return (zio); 353 354 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE; 355 356 if (zio->io_type == ZIO_TYPE_READ) 357 zio->io_vdev_tree = &vq->vq_read_tree; 358 else 359 zio->io_vdev_tree = &vq->vq_write_tree; 360 361 mutex_enter(&vq->vq_lock); 362 363 zio->io_deadline = (lbolt64 >> zfs_vdev_time_shift) + zio->io_priority; 364 365 vdev_queue_io_add(vq, zio); 366 367 nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending); 368 369 mutex_exit(&vq->vq_lock); 370 371 if (nio == NULL) 372 return (NULL); 373 374 if (nio->io_done == vdev_queue_agg_io_done) { 375 zio_nowait(nio); 376 return (NULL); 377 } 378 379 return (nio); 380 } 381 382 void 383 vdev_queue_io_done(zio_t *zio) 384 { 385 vdev_queue_t *vq = &zio->io_vd->vdev_queue; 386 387 mutex_enter(&vq->vq_lock); 388 389 avl_remove(&vq->vq_pending_tree, zio); 390 391 for (int i = 0; i < zfs_vdev_ramp_rate; i++) { 392 zio_t *nio = vdev_queue_io_to_issue(vq, zfs_vdev_max_pending); 393 if (nio == NULL) 394 break; 395 mutex_exit(&vq->vq_lock); 396 if (nio->io_done == vdev_queue_agg_io_done) { 397 zio_nowait(nio); 398 } else { 399 zio_vdev_io_reissue(nio); 400 zio_execute(nio); 401 } 402 mutex_enter(&vq->vq_lock); 403 } 404 405 mutex_exit(&vq->vq_lock); 406 } 407