cfq-iosched.c 102 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6
/*
 *  CFQ, or complete fairness queueing, disk scheduler.
 *
 *  Based on ideas from a previously unfinished io
 *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
 *
7
 *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
Linus Torvalds's avatar
Linus Torvalds committed
8 9
 */
#include <linux/module.h>
10
#include <linux/slab.h>
Al Viro's avatar
Al Viro committed
11 12
#include <linux/blkdev.h>
#include <linux/elevator.h>
Randy Dunlap's avatar
Randy Dunlap committed
13
#include <linux/jiffies.h>
Linus Torvalds's avatar
Linus Torvalds committed
14
#include <linux/rbtree.h>
15
#include <linux/ioprio.h>
16
#include <linux/blktrace_api.h>
17
#include "cfq.h"
Linus Torvalds's avatar
Linus Torvalds committed
18 19 20 21

/*
 * tunables
 */
22
/* max queue in one round of service */
Shaohua Li's avatar
Shaohua Li committed
23
static const int cfq_quantum = 8;
24
static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
25 26 27 28
/* maximum backwards seek, in KiB */
static const int cfq_back_max = 16 * 1024;
/* penalty of a backwards seek */
static const int cfq_back_penalty = 2;
29
static const int cfq_slice_sync = HZ / 10;
Jens Axboe's avatar
Jens Axboe committed
30
static int cfq_slice_async = HZ / 25;
31
static const int cfq_slice_async_rq = 2;
32
static int cfq_slice_idle = HZ / 125;
33 34
static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
static const int cfq_hist_divisor = 4;
35

36
/*
37
 * offset from end of service tree
38
 */
39
#define CFQ_IDLE_DELAY		(HZ / 5)
40 41 42 43 44 45

/*
 * below this threshold, we consider thinktime immediate
 */
#define CFQ_MIN_TT		(2)

46
#define CFQ_SLICE_SCALE		(5)
47
#define CFQ_HW_QUEUE_MIN	(5)
48
#define CFQ_SERVICE_SHIFT       12
49

50
#define CFQQ_SEEK_THR		(sector_t)(8 * 100)
51
#define CFQQ_CLOSE_THR		(sector_t)(8 * 1024)
52
#define CFQQ_SECT_THR_NONROT	(sector_t)(2 * 32)
53
#define CFQQ_SEEKY(cfqq)	(hweight32(cfqq->seek_history) > 32/8)
54

55 56
#define RQ_CIC(rq)		\
	((struct cfq_io_context *) (rq)->elevator_private)
57
#define RQ_CFQQ(rq)		(struct cfq_queue *) ((rq)->elevator_private2)
58
#define RQ_CFQG(rq)		(struct cfq_group *) ((rq)->elevator_private3)
Linus Torvalds's avatar
Linus Torvalds committed
59

60 61
static struct kmem_cache *cfq_pool;
static struct kmem_cache *cfq_ioc_pool;
Linus Torvalds's avatar
Linus Torvalds committed
62

63
static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
64
static struct completion *ioc_gone;
65
static DEFINE_SPINLOCK(ioc_gone_lock);
66

67 68 69
static DEFINE_SPINLOCK(cic_index_lock);
static DEFINE_IDA(cic_index_ida);

70 71 72 73
#define CFQ_PRIO_LISTS		IOPRIO_BE_NR
#define cfq_class_idle(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define cfq_class_rt(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_RT)

74
#define sample_valid(samples)	((samples) > 80)
75
#define rb_entry_cfqg(node)	rb_entry((node), struct cfq_group, rb_node)
76

77 78 79 80 81 82 83 84 85
/*
 * Most of our rbtree usage is for sorting with min extraction, so
 * if we cache the leftmost node we don't have to walk down the tree
 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
 * move this into the elevator for the rq sorting as well.
 */
struct cfq_rb_root {
	struct rb_root rb;
	struct rb_node *left;
86
	unsigned count;
87
	unsigned total_weight;
88
	u64 min_vdisktime;
89
	struct rb_node *active;
90
};
91 92
#define CFQ_RB_ROOT	(struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
			.count = 0, .min_vdisktime = 0, }
93

94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122
/*
 * Per process-grouping structure
 */
struct cfq_queue {
	/* reference count */
	atomic_t ref;
	/* various state flags, see below */
	unsigned int flags;
	/* parent cfq_data */
	struct cfq_data *cfqd;
	/* service_tree member */
	struct rb_node rb_node;
	/* service_tree key */
	unsigned long rb_key;
	/* prio tree member */
	struct rb_node p_node;
	/* prio tree root we belong to, if any */
	struct rb_root *p_root;
	/* sorted list of pending requests */
	struct rb_root sort_list;
	/* if fifo isn't expired, next request to serve */
	struct request *next_rq;
	/* requests queued in sort_list */
	int queued[2];
	/* currently allocated requests */
	int allocated[2];
	/* fifo list of requests in sort_list */
	struct list_head fifo;

123 124
	/* time when queue got scheduled in to dispatch first request. */
	unsigned long dispatch_start;
125
	unsigned int allocated_slice;
126
	unsigned int slice_dispatch;
127 128
	/* time when first request from queue completed and slice started. */
	unsigned long slice_start;
129 130 131 132 133 134 135 136 137 138 139 140
	unsigned long slice_end;
	long slice_resid;

	/* pending metadata requests */
	int meta_pending;
	/* number of requests that are on the dispatch list or inside driver */
	int dispatched;

	/* io prio of this group */
	unsigned short ioprio, org_ioprio;
	unsigned short ioprio_class, org_ioprio_class;

141 142
	pid_t pid;

143
	u32 seek_history;
144 145
	sector_t last_request_pos;

146
	struct cfq_rb_root *service_tree;
Jeff Moyer's avatar
Jeff Moyer committed
147
	struct cfq_queue *new_cfqq;
148
	struct cfq_group *cfqg;
149
	struct cfq_group *orig_cfqg;
150 151
};

152
/*
153
 * First index in the service_trees.
154 155 156 157
 * IDLE is handled separately, so it has negative index
 */
enum wl_prio_t {
	BE_WORKLOAD = 0,
158 159
	RT_WORKLOAD = 1,
	IDLE_WORKLOAD = 2,
160 161
};

162 163 164 165 166 167 168 169 170
/*
 * Second index in the service_trees.
 */
enum wl_type_t {
	ASYNC_WORKLOAD = 0,
	SYNC_NOIDLE_WORKLOAD = 1,
	SYNC_WORKLOAD = 2
};

171 172
/* This is per cgroup per device grouping structure */
struct cfq_group {
173 174 175 176 177
	/* group service_tree member */
	struct rb_node rb_node;

	/* group service_tree key */
	u64 vdisktime;
178
	unsigned int weight;
179 180 181 182 183
	bool on_st;

	/* number of cfqq currently on this group */
	int nr_cfqq;

184 185
	/* Per group busy queus average. Useful for workload slice calc. */
	unsigned int busy_queues_avg[2];
186 187 188 189 190 191
	/*
	 * rr lists of queues with requests, onle rr for each priority class.
	 * Counts are embedded in the cfq_rb_root
	 */
	struct cfq_rb_root service_trees[2][3];
	struct cfq_rb_root service_tree_idle;
192 193 194 195

	unsigned long saved_workload_slice;
	enum wl_type_t saved_workload;
	enum wl_prio_t saved_serving_prio;
196 197 198
	struct blkio_group blkg;
#ifdef CONFIG_CFQ_GROUP_IOSCHED
	struct hlist_node cfqd_node;
199
	atomic_t ref;
200
#endif
201
};
202

203 204 205
/*
 * Per block device queue structure
 */
Linus Torvalds's avatar
Linus Torvalds committed
206
struct cfq_data {
207
	struct request_queue *queue;
208 209
	/* Root service tree for cfq_groups */
	struct cfq_rb_root grp_service_tree;
210
	struct cfq_group root_group;
211

212 213
	/*
	 * The priority currently being served
214
	 */
215
	enum wl_prio_t serving_prio;
216 217
	enum wl_type_t serving_type;
	unsigned long workload_expires;
218
	struct cfq_group *serving_group;
219
	bool noidle_tree_requires_idle;
220 221 222 223 224 225 226 227

	/*
	 * Each priority tree is sorted by next_request position.  These
	 * trees are used when determining if two or more queues are
	 * interleaving requests (see cfq_close_cooperator).
	 */
	struct rb_root prio_trees[CFQ_PRIO_LISTS];

228 229
	unsigned int busy_queues;

230 231
	int rq_in_driver;
	int rq_in_flight[2];
232 233 234 235 236

	/*
	 * queue-depth detection
	 */
	int rq_queued;
237
	int hw_tag;
238 239 240 241 242 243 244 245
	/*
	 * hw_tag can be
	 * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
	 *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
	 *  0 => no NCQ
	 */
	int hw_tag_est_depth;
	unsigned int hw_tag_samples;
Linus Torvalds's avatar
Linus Torvalds committed
246

247 248 249 250
	/*
	 * idle window management
	 */
	struct timer_list idle_slice_timer;
251
	struct work_struct unplug_work;
Linus Torvalds's avatar
Linus Torvalds committed
252

253 254 255
	struct cfq_queue *active_queue;
	struct cfq_io_context *active_cic;

256 257 258 259 260
	/*
	 * async queue for each priority case
	 */
	struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
	struct cfq_queue *async_idle_cfqq;
261

Jens Axboe's avatar
Jens Axboe committed
262
	sector_t last_position;
Linus Torvalds's avatar
Linus Torvalds committed
263 264 265 266 267

	/*
	 * tunables, see top of file
	 */
	unsigned int cfq_quantum;
268
	unsigned int cfq_fifo_expire[2];
Linus Torvalds's avatar
Linus Torvalds committed
269 270
	unsigned int cfq_back_penalty;
	unsigned int cfq_back_max;
271 272 273
	unsigned int cfq_slice[2];
	unsigned int cfq_slice_async_rq;
	unsigned int cfq_slice_idle;
274
	unsigned int cfq_latency;
275
	unsigned int cfq_group_isolation;
276

277
	unsigned int cic_index;
278
	struct list_head cic_list;
Linus Torvalds's avatar
Linus Torvalds committed
279

280 281 282 283
	/*
	 * Fallback dummy cfqq for extreme OOM conditions
	 */
	struct cfq_queue oom_cfqq;
284

285
	unsigned long last_delayed_sync;
286 287 288

	/* List of cfq groups being managed on this device*/
	struct hlist_head cfqg_list;
289
	struct rcu_head rcu;
Linus Torvalds's avatar
Linus Torvalds committed
290 291
};

292 293
static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);

294 295
static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
					    enum wl_prio_t prio,
296
					    enum wl_type_t type)
297
{
298 299 300
	if (!cfqg)
		return NULL;

301
	if (prio == IDLE_WORKLOAD)
302
		return &cfqg->service_tree_idle;
303

304
	return &cfqg->service_trees[prio][type];
305 306
}

Jens Axboe's avatar
Jens Axboe committed
307
enum cfqq_state_flags {
308 309
	CFQ_CFQQ_FLAG_on_rr = 0,	/* on round-robin busy list */
	CFQ_CFQQ_FLAG_wait_request,	/* waiting for a request */
310
	CFQ_CFQQ_FLAG_must_dispatch,	/* must be allowed a dispatch */
311 312 313 314
	CFQ_CFQQ_FLAG_must_alloc_slice,	/* per-slice must_alloc flag */
	CFQ_CFQQ_FLAG_fifo_expire,	/* FIFO checked in this slice */
	CFQ_CFQQ_FLAG_idle_window,	/* slice idling enabled */
	CFQ_CFQQ_FLAG_prio_changed,	/* task priority has changed */
315
	CFQ_CFQQ_FLAG_slice_new,	/* no requests dispatched in slice */
316
	CFQ_CFQQ_FLAG_sync,		/* synchronous queue */
317
	CFQ_CFQQ_FLAG_coop,		/* cfqq is shared */
318
	CFQ_CFQQ_FLAG_split_coop,	/* shared cfqq will be splitted */
319
	CFQ_CFQQ_FLAG_deep,		/* sync cfqq experienced large depth */
320
	CFQ_CFQQ_FLAG_wait_busy,	/* Waiting for next request */
Jens Axboe's avatar
Jens Axboe committed
321 322 323 324 325
};

#define CFQ_CFQQ_FNS(name)						\
static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)		\
{									\
326
	(cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);			\
Jens Axboe's avatar
Jens Axboe committed
327 328 329
}									\
static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)	\
{									\
330
	(cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);			\
Jens Axboe's avatar
Jens Axboe committed
331 332 333
}									\
static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)		\
{									\
334
	return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;	\
Jens Axboe's avatar
Jens Axboe committed
335 336 337 338
}

CFQ_CFQQ_FNS(on_rr);
CFQ_CFQQ_FNS(wait_request);
339
CFQ_CFQQ_FNS(must_dispatch);
Jens Axboe's avatar
Jens Axboe committed
340 341 342 343
CFQ_CFQQ_FNS(must_alloc_slice);
CFQ_CFQQ_FNS(fifo_expire);
CFQ_CFQQ_FNS(idle_window);
CFQ_CFQQ_FNS(prio_changed);
344
CFQ_CFQQ_FNS(slice_new);
345
CFQ_CFQQ_FNS(sync);
346
CFQ_CFQQ_FNS(coop);
347
CFQ_CFQQ_FNS(split_coop);
348
CFQ_CFQQ_FNS(deep);
349
CFQ_CFQQ_FNS(wait_busy);
Jens Axboe's avatar
Jens Axboe committed
350 351
#undef CFQ_CFQQ_FNS

352
#ifdef CONFIG_CFQ_GROUP_IOSCHED
353 354 355 356 357 358 359 360 361 362
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	\
	blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
			cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
			blkg_path(&(cfqq)->cfqg->blkg), ##args);

#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)				\
	blk_add_trace_msg((cfqd)->queue, "%s " fmt,			\
				blkg_path(&(cfqg)->blkg), ##args);      \

#else
363 364
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	\
	blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
365 366
#define cfq_log_cfqg(cfqd, cfqg, fmt, args...)		do {} while (0);
#endif
367 368 369
#define cfq_log(cfqd, fmt, args...)	\
	blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)

370 371 372 373 374 375 376 377 378 379 380
/* Traverses through cfq group service trees */
#define for_each_cfqg_st(cfqg, i, j, st) \
	for (i = 0; i <= IDLE_WORKLOAD; i++) \
		for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
			: &cfqg->service_tree_idle; \
			(i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
			(i == IDLE_WORKLOAD && j == 0); \
			j++, st = i < IDLE_WORKLOAD ? \
			&cfqg->service_trees[i][j]: NULL) \


381 382 383 384 385 386 387 388 389
static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
{
	if (cfq_class_idle(cfqq))
		return IDLE_WORKLOAD;
	if (cfq_class_rt(cfqq))
		return RT_WORKLOAD;
	return BE_WORKLOAD;
}

390 391 392 393 394 395 396 397 398 399

static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
{
	if (!cfq_cfqq_sync(cfqq))
		return ASYNC_WORKLOAD;
	if (!cfq_cfqq_idle_window(cfqq))
		return SYNC_NOIDLE_WORKLOAD;
	return SYNC_WORKLOAD;
}

400 401 402
static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
					struct cfq_data *cfqd,
					struct cfq_group *cfqg)
403 404
{
	if (wl == IDLE_WORKLOAD)
405
		return cfqg->service_tree_idle.count;
406

407 408 409
	return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
		+ cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
		+ cfqg->service_trees[wl][SYNC_WORKLOAD].count;
410 411
}

412 413 414 415 416 417 418
static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
					struct cfq_group *cfqg)
{
	return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
		+ cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
}

419
static void cfq_dispatch_insert(struct request_queue *, struct request *);
420
static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
421
				       struct io_context *, gfp_t);
422
static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
423 424 425
						struct io_context *);

static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
426
					    bool is_sync)
427
{
428
	return cic->cfqq[is_sync];
429 430 431
}

static inline void cic_set_cfqq(struct cfq_io_context *cic,
432
				struct cfq_queue *cfqq, bool is_sync)
433
{
434
	cic->cfqq[is_sync] = cfqq;
435 436
}

437
#define CIC_DEAD_KEY	1ul
438
#define CIC_DEAD_INDEX_SHIFT	1
439 440 441

static inline void *cfqd_dead_key(struct cfq_data *cfqd)
{
442
	return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY);
443 444 445 446 447 448 449 450 451 452 453 454
}

static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
{
	struct cfq_data *cfqd = cic->key;

	if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY))
		return NULL;

	return cfqd;
}

455 456 457 458
/*
 * We regard a request as SYNC, if it's either a read or has the SYNC bit
 * set (in which case it could also be direct WRITE).
 */
459
static inline bool cfq_bio_sync(struct bio *bio)
460
{
461
	return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
462
}
Linus Torvalds's avatar
Linus Torvalds committed
463

Andrew Morton's avatar
Andrew Morton committed
464 465 466 467
/*
 * scheduler run of queue, if there are requests pending and no one in the
 * driver that will restart queueing
 */
468
static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
Andrew Morton's avatar
Andrew Morton committed
469
{
470 471
	if (cfqd->busy_queues) {
		cfq_log(cfqd, "schedule dispatch");
472
		kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
473
	}
Andrew Morton's avatar
Andrew Morton committed
474 475
}

476
static int cfq_queue_empty(struct request_queue *q)
Andrew Morton's avatar
Andrew Morton committed
477 478 479
{
	struct cfq_data *cfqd = q->elevator->elevator_data;

480
	return !cfqd->rq_queued;
Andrew Morton's avatar
Andrew Morton committed
481 482
}

483 484 485 486 487
/*
 * Scale schedule slice based on io priority. Use the sync time slice only
 * if a queue is marked sync and has sync io queued. A sync queue with async
 * io only, should not get full sync slice length.
 */
488
static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
489
				 unsigned short prio)
490
{
491
	const int base_slice = cfqd->cfq_slice[sync];
492

493 494 495 496
	WARN_ON(prio >= IOPRIO_BE_NR);

	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
}
497

498 499 500 501
static inline int
cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
	return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
502 503
}

504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548
static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
{
	u64 d = delta << CFQ_SERVICE_SHIFT;

	d = d * BLKIO_WEIGHT_DEFAULT;
	do_div(d, cfqg->weight);
	return d;
}

static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
	s64 delta = (s64)(vdisktime - min_vdisktime);
	if (delta > 0)
		min_vdisktime = vdisktime;

	return min_vdisktime;
}

static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
	s64 delta = (s64)(vdisktime - min_vdisktime);
	if (delta < 0)
		min_vdisktime = vdisktime;

	return min_vdisktime;
}

static void update_min_vdisktime(struct cfq_rb_root *st)
{
	u64 vdisktime = st->min_vdisktime;
	struct cfq_group *cfqg;

	if (st->active) {
		cfqg = rb_entry_cfqg(st->active);
		vdisktime = cfqg->vdisktime;
	}

	if (st->left) {
		cfqg = rb_entry_cfqg(st->left);
		vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
	}

	st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
}

549 550 551 552 553 554
/*
 * get averaged number of queues of RT/BE priority.
 * average is updated, with a formula that gives more weight to higher numbers,
 * to quickly follows sudden increases and decrease slowly
 */

555 556
static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
					struct cfq_group *cfqg, bool rt)
557
{
558 559 560
	unsigned min_q, max_q;
	unsigned mult  = cfq_hist_divisor - 1;
	unsigned round = cfq_hist_divisor / 2;
561
	unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
562

563 564 565
	min_q = min(cfqg->busy_queues_avg[rt], busy);
	max_q = max(cfqg->busy_queues_avg[rt], busy);
	cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
566
		cfq_hist_divisor;
567 568 569 570 571 572 573 574 575
	return cfqg->busy_queues_avg[rt];
}

static inline unsigned
cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
	struct cfq_rb_root *st = &cfqd->grp_service_tree;

	return cfq_target_latency * cfqg->weight / st->total_weight;
576 577
}

578 579 580
static inline void
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
581 582
	unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
	if (cfqd->cfq_latency) {
583 584 585 586 587 588
		/*
		 * interested queues (we consider only the ones with the same
		 * priority class in the cfq group)
		 */
		unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
						cfq_class_rt(cfqq));
589 590
		unsigned sync_slice = cfqd->cfq_slice[1];
		unsigned expect_latency = sync_slice * iq;
591 592 593
		unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);

		if (expect_latency > group_slice) {
594 595 596 597 598 599 600
			unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
			/* scale low_slice according to IO priority
			 * and sync vs async */
			unsigned low_slice =
				min(slice, base_low_slice * slice / sync_slice);
			/* the adapted slice value is scaled to fit all iqs
			 * into the target latency */
601
			slice = max(slice * group_slice / expect_latency,
602 603 604
				    low_slice);
		}
	}
605
	cfqq->slice_start = jiffies;
606
	cfqq->slice_end = jiffies + slice;
607
	cfqq->allocated_slice = slice;
608
	cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
609 610 611 612 613 614 615
}

/*
 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
 * isn't valid until the first request from the dispatch is activated
 * and the slice time set.
 */
616
static inline bool cfq_slice_used(struct cfq_queue *cfqq)
617 618 619 620 621 622 623 624 625
{
	if (cfq_cfqq_slice_new(cfqq))
		return 0;
	if (time_before(jiffies, cfqq->slice_end))
		return 0;

	return 1;
}

Linus Torvalds's avatar
Linus Torvalds committed
626
/*
Jens Axboe's avatar
Jens Axboe committed
627
 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
Linus Torvalds's avatar
Linus Torvalds committed
628
 * We choose the request that is closest to the head right now. Distance
629
 * behind the head is penalized and only allowed to a certain extent.
Linus Torvalds's avatar
Linus Torvalds committed
630
 */
Jens Axboe's avatar
Jens Axboe committed
631
static struct request *
632
cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
Linus Torvalds's avatar
Linus Torvalds committed
633
{
634
	sector_t s1, s2, d1 = 0, d2 = 0;
Linus Torvalds's avatar
Linus Torvalds committed
635
	unsigned long back_max;
636 637 638
#define CFQ_RQ1_WRAP	0x01 /* request 1 wraps */
#define CFQ_RQ2_WRAP	0x02 /* request 2 wraps */
	unsigned wrap = 0; /* bit mask: requests behind the disk head? */
Linus Torvalds's avatar
Linus Torvalds committed
639

Jens Axboe's avatar
Jens Axboe committed
640 641 642 643
	if (rq1 == NULL || rq1 == rq2)
		return rq2;
	if (rq2 == NULL)
		return rq1;
644

Jens Axboe's avatar
Jens Axboe committed
645 646 647 648
	if (rq_is_sync(rq1) && !rq_is_sync(rq2))
		return rq1;
	else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
		return rq2;
649
	if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
650
		return rq1;
651 652
	else if ((rq2->cmd_flags & REQ_META) &&
		 !(rq1->cmd_flags & REQ_META))
653
		return rq2;
Linus Torvalds's avatar
Linus Torvalds committed
654

655 656
	s1 = blk_rq_pos(rq1);
	s2 = blk_rq_pos(rq2);
Linus Torvalds's avatar
Linus Torvalds committed
657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672

	/*
	 * by definition, 1KiB is 2 sectors
	 */
	back_max = cfqd->cfq_back_max * 2;

	/*
	 * Strict one way elevator _except_ in the case where we allow
	 * short backward seeks which are biased as twice the cost of a
	 * similar forward seek.
	 */
	if (s1 >= last)
		d1 = s1 - last;
	else if (s1 + back_max >= last)
		d1 = (last - s1) * cfqd->cfq_back_penalty;
	else
673
		wrap |= CFQ_RQ1_WRAP;
Linus Torvalds's avatar
Linus Torvalds committed
674 675 676 677 678 679

	if (s2 >= last)
		d2 = s2 - last;
	else if (s2 + back_max >= last)
		d2 = (last - s2) * cfqd->cfq_back_penalty;
	else
680
		wrap |= CFQ_RQ2_WRAP;
Linus Torvalds's avatar
Linus Torvalds committed
681 682

	/* Found required data */
683 684 685 686 687 688

	/*
	 * By doing switch() on the bit mask "wrap" we avoid having to
	 * check two variables for all permutations: --> faster!
	 */
	switch (wrap) {
Jens Axboe's avatar
Jens Axboe committed
689
	case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
690
		if (d1 < d2)
Jens Axboe's avatar
Jens Axboe committed
691
			return rq1;
692
		else if (d2 < d1)
Jens Axboe's avatar
Jens Axboe committed
693
			return rq2;
694 695
		else {
			if (s1 >= s2)
Jens Axboe's avatar
Jens Axboe committed
696
				return rq1;
697
			else
Jens Axboe's avatar
Jens Axboe committed
698
				return rq2;
699
		}
Linus Torvalds's avatar
Linus Torvalds committed
700

701
	case CFQ_RQ2_WRAP:
Jens Axboe's avatar
Jens Axboe committed
702
		return rq1;
703
	case CFQ_RQ1_WRAP:
Jens Axboe's avatar
Jens Axboe committed
704 705
		return rq2;
	case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
706 707 708 709 710 711 712 713
	default:
		/*
		 * Since both rqs are wrapped,
		 * start with the one that's further behind head
		 * (--> only *one* back seek required),
		 * since back seek takes more time than forward.
		 */
		if (s1 <= s2)
Jens Axboe's avatar
Jens Axboe committed
714
			return rq1;
Linus Torvalds's avatar
Linus Torvalds committed
715
		else
Jens Axboe's avatar
Jens Axboe committed
716
			return rq2;
Linus Torvalds's avatar
Linus Torvalds committed
717 718 719
	}
}

720 721 722
/*
 * The below is leftmost cache rbtree addon
 */
723
static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
724
{
725 726 727 728
	/* Service tree is empty */
	if (!root->count)
		return NULL;

729 730 731
	if (!root->left)
		root->left = rb_first(&root->rb);

732 733 734 735
	if (root->left)
		return rb_entry(root->left, struct cfq_queue, rb_node);

	return NULL;
736 737
}

738 739 740 741 742 743 744 745 746 747 748
static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
{
	if (!root->left)
		root->left = rb_first(&root->rb);

	if (root->left)
		return rb_entry_cfqg(root->left);

	return NULL;
}

749 750 751 752 753 754
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
	rb_erase(n, root);
	RB_CLEAR_NODE(n);
}

755 756 757 758
static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
	if (root->left == n)
		root->left = NULL;
759
	rb_erase_init(n, &root->rb);
760
	--root->count;
761 762
}

Linus Torvalds's avatar
Linus Torvalds committed
763 764 765
/*
 * would be nice to take fifo expire time into account as well
 */
Jens Axboe's avatar
Jens Axboe committed
766 767 768
static struct request *
cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
		  struct request *last)
Linus Torvalds's avatar
Linus Torvalds committed
769
{
770 771
	struct rb_node *rbnext = rb_next(&last->rb_node);
	struct rb_node *rbprev = rb_prev(&last->rb_node);
Jens Axboe's avatar
Jens Axboe committed
772
	struct request *next = NULL, *prev = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
773

774
	BUG_ON(RB_EMPTY_NODE(&last->rb_node));
Linus Torvalds's avatar
Linus Torvalds committed
775 776

	if (rbprev)
Jens Axboe's avatar
Jens Axboe committed
777
		prev = rb_entry_rq(rbprev);
Linus Torvalds's avatar
Linus Torvalds committed
778

779
	if (rbnext)
Jens Axboe's avatar
Jens Axboe committed
780
		next = rb_entry_rq(rbnext);
781 782 783
	else {
		rbnext = rb_first(&cfqq->sort_list);
		if (rbnext && rbnext != &last->rb_node)
Jens Axboe's avatar
Jens Axboe committed
784
			next = rb_entry_rq(rbnext);
785
	}
Linus Torvalds's avatar
Linus Torvalds committed
786

787
	return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
Linus Torvalds's avatar
Linus Torvalds committed
788 789
}

790 791
static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
				      struct cfq_queue *cfqq)
Linus Torvalds's avatar
Linus Torvalds committed
792
{
793 794 795
	/*
	 * just an approximation, should be ok.
	 */
796
	return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
797
		       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
798 799
}

800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858
static inline s64
cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
	return cfqg->vdisktime - st->min_vdisktime;
}

static void
__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
	struct rb_node **node = &st->rb.rb_node;
	struct rb_node *parent = NULL;
	struct cfq_group *__cfqg;
	s64 key = cfqg_key(st, cfqg);
	int left = 1;

	while (*node != NULL) {
		parent = *node;
		__cfqg = rb_entry_cfqg(parent);

		if (key < cfqg_key(st, __cfqg))
			node = &parent->rb_left;
		else {
			node = &parent->rb_right;
			left = 0;
		}
	}

	if (left)
		st->left = &cfqg->rb_node;

	rb_link_node(&cfqg->rb_node, parent, node);
	rb_insert_color(&cfqg->rb_node, &st->rb);
}

static void
cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
	struct cfq_rb_root *st = &cfqd->grp_service_tree;
	struct cfq_group *__cfqg;
	struct rb_node *n;

	cfqg->nr_cfqq++;
	if (cfqg->on_st)
		return;

	/*
	 * Currently put the group at the end. Later implement something
	 * so that groups get lesser vtime based on their weights, so that
	 * if group does not loose all if it was not continously backlogged.
	 */
	n = rb_last(&st->rb);
	if (n) {
		__cfqg = rb_entry_cfqg(n);
		cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
	} else
		cfqg->vdisktime = st->min_vdisktime;

	__cfq_group_service_tree_add(st, cfqg);
	cfqg->on_st = true;
859
	st->total_weight += cfqg->weight;
860 861 862 863 864 865 866
}

static void
cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
	struct cfq_rb_root *st = &cfqd->grp_service_tree;

867 868 869
	if (st->active == &cfqg->rb_node)
		st->active = NULL;

870 871
	BUG_ON(cfqg->nr_cfqq < 1);
	cfqg->nr_cfqq--;
872

873 874 875 876
	/* If there are other cfq queues under this group, don't delete it */
	if (cfqg->nr_cfqq)
		return;

877
	cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
878
	cfqg->on_st = false;
879
	st->total_weight -= cfqg->weight;
880 881
	if (!RB_EMPTY_NODE(&cfqg->rb_node))
		cfq_rb_erase(&cfqg->rb_node, st);
882
	cfqg->saved_workload_slice = 0;
883
	cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
884 885 886 887
}

static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
{
888
	unsigned int slice_used;
889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904

	/*
	 * Queue got expired before even a single request completed or
	 * got expired immediately after first request completion.
	 */
	if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
		/*
		 * Also charge the seek time incurred to the group, otherwise
		 * if there are mutiple queues in the group, each can dispatch
		 * a single request on seeky media and cause lots of seek time
		 * and group will never know it.
		 */
		slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
					1);
	} else {
		slice_used = jiffies - cfqq->slice_start;
905 906
		if (slice_used > cfqq->allocated_slice)
			slice_used = cfqq->allocated_slice;
907 908
	}

909
	cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
910 911 912 913
	return slice_used;
}

static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
914
				struct cfq_queue *cfqq)
915 916
{
	struct cfq_rb_root *st = &cfqd->grp_service_tree;
917 918 919 920 921 922
	unsigned int used_sl, charge_sl;
	int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
			- cfqg->service_tree_idle.count;

	BUG_ON(nr_sync < 0);
	used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
923

924 925
	if (!cfq_cfqq_sync(cfqq) && !nr_sync)
		charge_sl = cfqq->allocated_slice;
926 927 928

	/* Can't update vdisktime while group is on service tree */
	cfq_rb_erase(&cfqg->rb_node, st);
929
	cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
930 931 932 933 934 935 936 937 938 939
	__cfq_group_service_tree_add(st, cfqg);

	/* This group is being expired. Save the context */
	if (time_after(cfqd->workload_expires, jiffies)) {
		cfqg->saved_workload_slice = cfqd->workload_expires
						- jiffies;
		cfqg->saved_workload = cfqd->serving_type;
		cfqg->saved_serving_prio = cfqd->serving_prio;
	} else
		cfqg->saved_workload_slice = 0;
940 941 942

	cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
					st->min_vdisktime);
943 944
	cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
	cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
945 946
}

947 948 949 950 951 952 953 954
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
{
	if (blkg)
		return container_of(blkg, struct cfq_group, blkg);
	return NULL;
}

955 956 957 958 959 960
void
cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
{
	cfqg_of_blkg(blkg)->weight = weight;
}

961 962 963 964 965 966 967 968
static struct cfq_group *
cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
{
	struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
	struct cfq_group *cfqg = NULL;
	void *key = cfqd;
	int i, j;
	struct cfq_rb_root *st;
969 970
	struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
	unsigned int major, minor;
971 972

	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
973 974 975 976 977
	if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
		sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
		cfqg->blkg.dev = MKDEV(major, minor);
		goto done;
	}
978 979 980 981 982 983 984 985 986 987 988
	if (cfqg || !create)
		goto done;

	cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
	if (!cfqg)
		goto done;

	for_each_cfqg_st(cfqg, i, j, st)
		*st = CFQ_RB_ROOT;
	RB_CLEAR_NODE(&cfqg->rb_node);

989 990 991 992 993 994 995 996
	/*
	 * Take the initial reference that will be released on destroy
	 * This can be thought of a joint reference by cgroup and
	 * elevator which will be dropped by either elevator exit
	 * or cgroup deletion path depending on who is exiting first.
	 */
	atomic_set(&cfqg->ref, 1);

997
	/* Add group onto cgroup list */
998
	sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
999
	cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
1000
					MKDEV(major, minor));
1001
	cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027

	/* Add group on cfqd list */
	hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);

done:
	return cfqg;
}

/*
 * Search for the cfq group current task belongs to. If create = 1, then also
 * create the cfq group if it does not exist. request_queue lock must be held.
 */
static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
{
	struct cgroup *cgroup;
	struct cfq_group *cfqg = NULL;

	rcu_read_lock();
	cgroup = task_cgroup(current, blkio_subsys_id);
	cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
	if (!cfqg && create)
		cfqg = &cfqd->root_group;
	rcu_read_unlock();
	return cfqg;
}

1028 1029 1030 1031 1032 1033
static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
	atomic_inc(&cfqg->ref);
	return cfqg;
}

1034 1035 1036 1037 1038 1039 1040
static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
{
	/* Currently, all async queues are mapped to root group */
	if (!cfq_cfqq_sync(cfqq))
		cfqg = &cfqq->cfqd->root_group;

	cfqq->cfqg = cfqg;
1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
	/* cfqq reference on cfqg */
	atomic_inc(&cfqq->cfqg->ref);
}

static void cfq_put_cfqg(struct cfq_group *cfqg)
{
	struct cfq_rb_root *st;
	int i, j;

	BUG_ON(atomic_read(&cfqg->ref) <= 0);
	if (!atomic_dec_and_test(&cfqg->ref))
		return;
	for_each_cfqg_st(cfqg, i, j, st)
		BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
	kfree(cfqg);
}

static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
	/* Something wrong if we are trying to remove same group twice */
	BUG_ON(hlist_unhashed(&cfqg->cfqd_node));

	hlist_del_init(&cfqg->cfqd_node);

	/*
	 * Put the reference taken at the time of creation so that when all
	 * queues are gone, group can be destroyed.
	 */
	cfq_put_cfqg(cfqg);
}

static void cfq_release_cfq_groups(struct cfq_data *cfqd)
{
	struct hlist_node *pos, *n;
	struct cfq_group *cfqg;

	hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
		/*
		 * If cgroup removal path got to blk_group first and removed
		 * it from cgroup list, then it will take care of destroying
		 * cfqg also.
		 */
1083
		if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
1084 1085
			cfq_destroy_cfqg(cfqd, cfqg);
	}
1086
}
1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111

/*
 * Blk cgroup controller notification saying that blkio_group object is being
 * delinked as associated cgroup object is going away. That also means that
 * no new IO will come in this group. So get rid of this group as soon as
 * any pending IO in the group is finished.
 *
 * This function is called under rcu_read_lock(). key is the rcu protected
 * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
 * read lock.
 *
 * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
 * it should not be NULL as even if elevator was exiting, cgroup deltion
 * path got to it first.
 */
void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
{
	unsigned long  flags;
	struct cfq_data *cfqd = key;

	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
	cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}

1112 1113 1114 1115 1116
#else /* GROUP_IOSCHED */
static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
{
	return &cfqd->root_group;
}
1117 1118 1119

static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
1120
	return cfqg;