46int zfs_vdev_min_pending = 4;
47
48/*
49 * The deadlines are grouped into buckets based on zfs_vdev_time_shift:
50 * deadline = pri + gethrtime() >> time_shift)
51 */
52int zfs_vdev_time_shift = 29; /* each bucket is 0.537 seconds */
53
54/* exponential I/O issue ramp-up rate */
55int zfs_vdev_ramp_rate = 2;
56
57/*
58 * To reduce IOPs, we aggregate small adjacent I/Os into one large I/O.
59 * For read I/Os, we also aggregate across small adjacency gaps; for writes
60 * we include spans of optional I/Os to aid aggregation at the disk even when
61 * they aren't able to help us aggregate at this level.
62 */
63int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
64int zfs_vdev_read_gap_limit = 32 << 10;
65int zfs_vdev_write_gap_limit = 4 << 10;
66
67SYSCTL_DECL(_vfs_zfs_vdev);
68TUNABLE_INT("vfs.zfs.vdev.max_pending", &zfs_vdev_max_pending);
69SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, max_pending, CTLFLAG_RW,
70 &zfs_vdev_max_pending, 0, "Maximum I/O requests pending on each device");
71TUNABLE_INT("vfs.zfs.vdev.min_pending", &zfs_vdev_min_pending);
72SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, min_pending, CTLFLAG_RW,
73 &zfs_vdev_min_pending, 0,
74 "Initial number of I/O requests pending to each device");
75TUNABLE_INT("vfs.zfs.vdev.time_shift", &zfs_vdev_time_shift);
76SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, time_shift, CTLFLAG_RW,
77 &zfs_vdev_time_shift, 0, "Used for calculating I/O request deadline");
78TUNABLE_INT("vfs.zfs.vdev.ramp_rate", &zfs_vdev_ramp_rate);
79SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, ramp_rate, CTLFLAG_RW,
80 &zfs_vdev_ramp_rate, 0, "Exponential I/O issue ramp-up rate");
81TUNABLE_INT("vfs.zfs.vdev.aggregation_limit", &zfs_vdev_aggregation_limit);
82SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, aggregation_limit, CTLFLAG_RW,
83 &zfs_vdev_aggregation_limit, 0,
84 "I/O requests are aggregated up to this size");
85TUNABLE_INT("vfs.zfs.vdev.read_gap_limit", &zfs_vdev_read_gap_limit);
86SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, read_gap_limit, CTLFLAG_RW,
87 &zfs_vdev_read_gap_limit, 0,
88 "Acceptable gap between two reads being aggregated");
89TUNABLE_INT("vfs.zfs.vdev.write_gap_limit", &zfs_vdev_write_gap_limit);
90SYSCTL_INT(_vfs_zfs_vdev, OID_AUTO, write_gap_limit, CTLFLAG_RW,
91 &zfs_vdev_write_gap_limit, 0,
92 "Acceptable gap between two writes being aggregated");
93
94/*
95 * Virtual device vector for disk I/O scheduling.
96 */
97int
98vdev_queue_deadline_compare(const void *x1, const void *x2)
99{
100 const zio_t *z1 = x1;
101 const zio_t *z2 = x2;
102
103 if (z1->io_deadline < z2->io_deadline)
104 return (-1);
105 if (z1->io_deadline > z2->io_deadline)
106 return (1);
107
108 if (z1->io_offset < z2->io_offset)
109 return (-1);
110 if (z1->io_offset > z2->io_offset)
111 return (1);
112
113 if (z1 < z2)
114 return (-1);
115 if (z1 > z2)
116 return (1);
117
118 return (0);
119}
120
121int
122vdev_queue_offset_compare(const void *x1, const void *x2)
123{
124 const zio_t *z1 = x1;
125 const zio_t *z2 = x2;
126
127 if (z1->io_offset < z2->io_offset)
128 return (-1);
129 if (z1->io_offset > z2->io_offset)
130 return (1);
131
132 if (z1 < z2)
133 return (-1);
134 if (z1 > z2)
135 return (1);
136
137 return (0);
138}
139
140void
141vdev_queue_init(vdev_t *vd)
142{
143 vdev_queue_t *vq = &vd->vdev_queue;
144
145 mutex_init(&vq->vq_lock, NULL, MUTEX_DEFAULT, NULL);
146
147 avl_create(&vq->vq_deadline_tree, vdev_queue_deadline_compare,
148 sizeof (zio_t), offsetof(struct zio, io_deadline_node));
149
150 avl_create(&vq->vq_read_tree, vdev_queue_offset_compare,
151 sizeof (zio_t), offsetof(struct zio, io_offset_node));
152
153 avl_create(&vq->vq_write_tree, vdev_queue_offset_compare,
154 sizeof (zio_t), offsetof(struct zio, io_offset_node));
155
156 avl_create(&vq->vq_pending_tree, vdev_queue_offset_compare,
157 sizeof (zio_t), offsetof(struct zio, io_offset_node));
158}
159
160void
161vdev_queue_fini(vdev_t *vd)
162{
163 vdev_queue_t *vq = &vd->vdev_queue;
164
165 avl_destroy(&vq->vq_deadline_tree);
166 avl_destroy(&vq->vq_read_tree);
167 avl_destroy(&vq->vq_write_tree);
168 avl_destroy(&vq->vq_pending_tree);
169
170 mutex_destroy(&vq->vq_lock);
171}
172
173static void
174vdev_queue_io_add(vdev_queue_t *vq, zio_t *zio)
175{
176 avl_add(&vq->vq_deadline_tree, zio);
177 avl_add(zio->io_vdev_tree, zio);
178}
179
180static void
181vdev_queue_io_remove(vdev_queue_t *vq, zio_t *zio)
182{
183 avl_remove(&vq->vq_deadline_tree, zio);
184 avl_remove(zio->io_vdev_tree, zio);
185}
186
187static void
188vdev_queue_agg_io_done(zio_t *aio)
189{
190 zio_t *pio;
191
192 while ((pio = zio_walk_parents(aio)) != NULL)
193 if (aio->io_type == ZIO_TYPE_READ)
194 bcopy((char *)aio->io_data + (pio->io_offset -
195 aio->io_offset), pio->io_data, pio->io_size);
196
197 zio_buf_free(aio->io_data, aio->io_size);
198}
199
200/*
201 * Compute the range spanned by two i/os, which is the endpoint of the last
202 * (lio->io_offset + lio->io_size) minus start of the first (fio->io_offset).
203 * Conveniently, the gap between fio and lio is given by -IO_SPAN(lio, fio);
204 * thus fio and lio are adjacent if and only if IO_SPAN(lio, fio) == 0.
205 */
206#define IO_SPAN(fio, lio) ((lio)->io_offset + (lio)->io_size - (fio)->io_offset)
207#define IO_GAP(fio, lio) (-IO_SPAN(lio, fio))
208
209static zio_t *
210vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
211{
212 zio_t *fio, *lio, *aio, *dio, *nio, *mio;
213 avl_tree_t *t;
214 int flags;
215 uint64_t maxspan = zfs_vdev_aggregation_limit;
216 uint64_t maxgap;
217 int stretch;
218
219again:
220 ASSERT(MUTEX_HELD(&vq->vq_lock));
221
222 if (avl_numnodes(&vq->vq_pending_tree) >= pending_limit ||
223 avl_numnodes(&vq->vq_deadline_tree) == 0)
224 return (NULL);
225
226 fio = lio = avl_first(&vq->vq_deadline_tree);
227
228 t = fio->io_vdev_tree;
229 flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
230 maxgap = (t == &vq->vq_read_tree) ? zfs_vdev_read_gap_limit : 0;
231
232 if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
233 /*
234 * We can aggregate I/Os that are sufficiently adjacent and of
235 * the same flavor, as expressed by the AGG_INHERIT flags.
236 * The latter requirement is necessary so that certain
237 * attributes of the I/O, such as whether it's a normal I/O
238 * or a scrub/resilver, can be preserved in the aggregate.
239 * We can include optional I/Os, but don't allow them
240 * to begin a range as they add no benefit in that situation.
241 */
242
243 /*
244 * We keep track of the last non-optional I/O.
245 */
246 mio = (fio->io_flags & ZIO_FLAG_OPTIONAL) ? NULL : fio;
247
248 /*
249 * Walk backwards through sufficiently contiguous I/Os
250 * recording the last non-option I/O.
251 */
252 while ((dio = AVL_PREV(t, fio)) != NULL &&
253 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
254 IO_SPAN(dio, lio) <= maxspan &&
255 IO_GAP(dio, fio) <= maxgap) {
256 fio = dio;
257 if (mio == NULL && !(fio->io_flags & ZIO_FLAG_OPTIONAL))
258 mio = fio;
259 }
260
261 /*
262 * Skip any initial optional I/Os.
263 */
264 while ((fio->io_flags & ZIO_FLAG_OPTIONAL) && fio != lio) {
265 fio = AVL_NEXT(t, fio);
266 ASSERT(fio != NULL);
267 }
268
269 /*
270 * Walk forward through sufficiently contiguous I/Os.
271 */
272 while ((dio = AVL_NEXT(t, lio)) != NULL &&
273 (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
274 IO_SPAN(fio, dio) <= maxspan &&
275 IO_GAP(lio, dio) <= maxgap) {
276 lio = dio;
277 if (!(lio->io_flags & ZIO_FLAG_OPTIONAL))
278 mio = lio;
279 }
280
281 /*
282 * Now that we've established the range of the I/O aggregation
283 * we must decide what to do with trailing optional I/Os.
284 * For reads, there's nothing to do. While we are unable to
285 * aggregate further, it's possible that a trailing optional
286 * I/O would allow the underlying device to aggregate with
287 * subsequent I/Os. We must therefore determine if the next
288 * non-optional I/O is close enough to make aggregation
289 * worthwhile.
290 */
291 stretch = B_FALSE;
292 if (t != &vq->vq_read_tree && mio != NULL) {
293 nio = lio;
294 while ((dio = AVL_NEXT(t, nio)) != NULL &&
295 IO_GAP(nio, dio) == 0 &&
296 IO_GAP(mio, dio) <= zfs_vdev_write_gap_limit) {
297 nio = dio;
298 if (!(nio->io_flags & ZIO_FLAG_OPTIONAL)) {
299 stretch = B_TRUE;
300 break;
301 }
302 }
303 }
304
305 if (stretch) {
306 /* This may be a no-op. */
307 VERIFY((dio = AVL_NEXT(t, lio)) != NULL);
308 dio->io_flags &= ~ZIO_FLAG_OPTIONAL;
309 } else {
310 while (lio != mio && lio != fio) {
311 ASSERT(lio->io_flags & ZIO_FLAG_OPTIONAL);
312 lio = AVL_PREV(t, lio);
313 ASSERT(lio != NULL);
314 }
315 }
316 }
317
318 if (fio != lio) {
319 uint64_t size = IO_SPAN(fio, lio);
320 ASSERT(size <= zfs_vdev_aggregation_limit);
321
322 aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
323 zio_buf_alloc(size), size, fio->io_type, ZIO_PRIORITY_AGG,
324 flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
325 vdev_queue_agg_io_done, NULL);
326 aio->io_timestamp = fio->io_timestamp;
327
328 nio = fio;
329 do {
330 dio = nio;
331 nio = AVL_NEXT(t, dio);
332 ASSERT(dio->io_type == aio->io_type);
333 ASSERT(dio->io_vdev_tree == t);
334
335 if (dio->io_flags & ZIO_FLAG_NODATA) {
336 ASSERT(dio->io_type == ZIO_TYPE_WRITE);
337 bzero((char *)aio->io_data + (dio->io_offset -
338 aio->io_offset), dio->io_size);
339 } else if (dio->io_type == ZIO_TYPE_WRITE) {
340 bcopy(dio->io_data, (char *)aio->io_data +
341 (dio->io_offset - aio->io_offset),
342 dio->io_size);
343 }
344
345 zio_add_child(dio, aio);
346 vdev_queue_io_remove(vq, dio);
347 zio_vdev_io_bypass(dio);
348 zio_execute(dio);
349 } while (dio != lio);
350
351 avl_add(&vq->vq_pending_tree, aio);
352
353 return (aio);
354 }
355
356 ASSERT(fio->io_vdev_tree == t);
357 vdev_queue_io_remove(vq, fio);
358
359 /*
360 * If the I/O is or was optional and therefore has no data, we need to
361 * simply discard it. We need to drop the vdev queue's lock to avoid a
362 * deadlock that we could encounter since this I/O will complete
363 * immediately.
364 */
365 if (fio->io_flags & ZIO_FLAG_NODATA) {
366 mutex_exit(&vq->vq_lock);
367 zio_vdev_io_bypass(fio);
368 zio_execute(fio);
369 mutex_enter(&vq->vq_lock);
370 goto again;
371 }
372
373 avl_add(&vq->vq_pending_tree, fio);
374
375 return (fio);
376}
377
378zio_t *
379vdev_queue_io(zio_t *zio)
380{
381 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
382 zio_t *nio;
383
384 ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);
385
386 if (zio->io_flags & ZIO_FLAG_DONT_QUEUE)
387 return (zio);
388
389 zio->io_flags |= ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE;
390
391 if (zio->io_type == ZIO_TYPE_READ)
392 zio->io_vdev_tree = &vq->vq_read_tree;
393 else
394 zio->io_vdev_tree = &vq->vq_write_tree;
395
396 mutex_enter(&vq->vq_lock);
397
398 zio->io_timestamp = gethrtime();
399 zio->io_deadline = (zio->io_timestamp >> zfs_vdev_time_shift) +
400 zio->io_priority;
401
402 vdev_queue_io_add(vq, zio);
403
404 nio = vdev_queue_io_to_issue(vq, zfs_vdev_min_pending);
405
406 mutex_exit(&vq->vq_lock);
407
408 if (nio == NULL)
409 return (NULL);
410
411 if (nio->io_done == vdev_queue_agg_io_done) {
412 zio_nowait(nio);
413 return (NULL);
414 }
415
416 return (nio);
417}
418
419void
420vdev_queue_io_done(zio_t *zio)
421{
422 vdev_queue_t *vq = &zio->io_vd->vdev_queue;
423
424 if (zio_injection_enabled)
425 delay(SEC_TO_TICK(zio_handle_io_delay(zio)));
426
427 mutex_enter(&vq->vq_lock);
428
429 avl_remove(&vq->vq_pending_tree, zio);
430
431 vq->vq_io_complete_ts = gethrtime();
432
433 for (int i = 0; i < zfs_vdev_ramp_rate; i++) {
434 zio_t *nio = vdev_queue_io_to_issue(vq, zfs_vdev_max_pending);
435 if (nio == NULL)
436 break;
437 mutex_exit(&vq->vq_lock);
438 if (nio->io_done == vdev_queue_agg_io_done) {
439 zio_nowait(nio);
440 } else {
441 zio_vdev_io_reissue(nio);
442 zio_execute(nio);
443 }
444 mutex_enter(&vq->vq_lock);
445 }
446
447 mutex_exit(&vq->vq_lock);
448}
|