Root/block/blk-throttle.c

1/*
2 * Interface for controlling IO bandwidth on a request queue
3 *
4 * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
5 */
6
7#include <linux/module.h>
8#include <linux/slab.h>
9#include <linux/blkdev.h>
10#include <linux/bio.h>
11#include <linux/blktrace_api.h>
12#include "blk-cgroup.h"
13#include "blk.h"
14
15/* Max dispatch from a group in 1 round */
16static int throtl_grp_quantum = 8;
17
18/* Total max dispatch from all groups in one round */
19static int throtl_quantum = 32;
20
21/* Throttling is performed over 100ms slice and after that slice is renewed */
22static unsigned long throtl_slice = HZ/10; /* 100 ms */
23
24static struct blkcg_policy blkcg_policy_throtl;
25
26/* A workqueue to queue throttle related work */
27static struct workqueue_struct *kthrotld_workqueue;
28static void throtl_schedule_delayed_work(struct throtl_data *td,
29                unsigned long delay);
30
31struct throtl_rb_root {
32    struct rb_root rb;
33    struct rb_node *left;
34    unsigned int count;
35    unsigned long min_disptime;
36};
37
38#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
39            .count = 0, .min_disptime = 0}
40
41#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
42
43/* Per-cpu group stats */
44struct tg_stats_cpu {
45    /* total bytes transferred */
46    struct blkg_rwstat service_bytes;
47    /* total IOs serviced, post merge */
48    struct blkg_rwstat serviced;
49};
50
51struct throtl_grp {
52    /* must be the first member */
53    struct blkg_policy_data pd;
54
55    /* active throtl group service_tree member */
56    struct rb_node rb_node;
57
58    /*
59     * Dispatch time in jiffies. This is the estimated time when group
60     * will unthrottle and is ready to dispatch more bio. It is used as
61     * key to sort active groups in service tree.
62     */
63    unsigned long disptime;
64
65    unsigned int flags;
66
67    /* Two lists for READ and WRITE */
68    struct bio_list bio_lists[2];
69
70    /* Number of queued bios on READ and WRITE lists */
71    unsigned int nr_queued[2];
72
73    /* bytes per second rate limits */
74    uint64_t bps[2];
75
76    /* IOPS limits */
77    unsigned int iops[2];
78
79    /* Number of bytes disptached in current slice */
80    uint64_t bytes_disp[2];
81    /* Number of bio's dispatched in current slice */
82    unsigned int io_disp[2];
83
84    /* When did we start a new slice */
85    unsigned long slice_start[2];
86    unsigned long slice_end[2];
87
88    /* Some throttle limits got updated for the group */
89    int limits_changed;
90
91    /* Per cpu stats pointer */
92    struct tg_stats_cpu __percpu *stats_cpu;
93
94    /* List of tgs waiting for per cpu stats memory to be allocated */
95    struct list_head stats_alloc_node;
96};
97
98struct throtl_data
99{
100    /* service tree for active throtl groups */
101    struct throtl_rb_root tg_service_tree;
102
103    struct request_queue *queue;
104
105    /* Total Number of queued bios on READ and WRITE lists */
106    unsigned int nr_queued[2];
107
108    /*
109     * number of total undestroyed groups
110     */
111    unsigned int nr_undestroyed_grps;
112
113    /* Work for dispatching throttled bios */
114    struct delayed_work throtl_work;
115
116    int limits_changed;
117};
118
119/* list and work item to allocate percpu group stats */
120static DEFINE_SPINLOCK(tg_stats_alloc_lock);
121static LIST_HEAD(tg_stats_alloc_list);
122
123static void tg_stats_alloc_fn(struct work_struct *);
124static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
125
126static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
127{
128    return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
129}
130
131static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
132{
133    return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
134}
135
136static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
137{
138    return pd_to_blkg(&tg->pd);
139}
140
141static inline struct throtl_grp *td_root_tg(struct throtl_data *td)
142{
143    return blkg_to_tg(td->queue->root_blkg);
144}
145
146enum tg_state_flags {
147    THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
148};
149
150#define THROTL_TG_FNS(name) \
151static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
152{ \
153    (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
154} \
155static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
156{ \
157    (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
158} \
159static inline int throtl_tg_##name(const struct throtl_grp *tg) \
160{ \
161    return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
162}
163
164THROTL_TG_FNS(on_rr);
165
166#define throtl_log_tg(td, tg, fmt, args...) do { \
167    char __pbuf[128]; \
168                                    \
169    blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf)); \
170    blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \
171} while (0)
172
173#define throtl_log(td, fmt, args...) \
174    blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
175
176static inline unsigned int total_nr_queued(struct throtl_data *td)
177{
178    return td->nr_queued[0] + td->nr_queued[1];
179}
180
181/*
182 * Worker for allocating per cpu stat for tgs. This is scheduled on the
183 * system_nrt_wq once there are some groups on the alloc_list waiting for
184 * allocation.
185 */
186static void tg_stats_alloc_fn(struct work_struct *work)
187{
188    static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
189    struct delayed_work *dwork = to_delayed_work(work);
190    bool empty = false;
191
192alloc_stats:
193    if (!stats_cpu) {
194        stats_cpu = alloc_percpu(struct tg_stats_cpu);
195        if (!stats_cpu) {
196            /* allocation failed, try again after some time */
197            queue_delayed_work(system_nrt_wq, dwork,
198                       msecs_to_jiffies(10));
199            return;
200        }
201    }
202
203    spin_lock_irq(&tg_stats_alloc_lock);
204
205    if (!list_empty(&tg_stats_alloc_list)) {
206        struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
207                             struct throtl_grp,
208                             stats_alloc_node);
209        swap(tg->stats_cpu, stats_cpu);
210        list_del_init(&tg->stats_alloc_node);
211    }
212
213    empty = list_empty(&tg_stats_alloc_list);
214    spin_unlock_irq(&tg_stats_alloc_lock);
215    if (!empty)
216        goto alloc_stats;
217}
218
219static void throtl_pd_init(struct blkcg_gq *blkg)
220{
221    struct throtl_grp *tg = blkg_to_tg(blkg);
222    unsigned long flags;
223
224    RB_CLEAR_NODE(&tg->rb_node);
225    bio_list_init(&tg->bio_lists[0]);
226    bio_list_init(&tg->bio_lists[1]);
227    tg->limits_changed = false;
228
229    tg->bps[READ] = -1;
230    tg->bps[WRITE] = -1;
231    tg->iops[READ] = -1;
232    tg->iops[WRITE] = -1;
233
234    /*
235     * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
236     * but percpu allocator can't be called from IO path. Queue tg on
237     * tg_stats_alloc_list and allocate from work item.
238     */
239    spin_lock_irqsave(&tg_stats_alloc_lock, flags);
240    list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
241    queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0);
242    spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
243}
244
245static void throtl_pd_exit(struct blkcg_gq *blkg)
246{
247    struct throtl_grp *tg = blkg_to_tg(blkg);
248    unsigned long flags;
249
250    spin_lock_irqsave(&tg_stats_alloc_lock, flags);
251    list_del_init(&tg->stats_alloc_node);
252    spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
253
254    free_percpu(tg->stats_cpu);
255}
256
257static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
258{
259    struct throtl_grp *tg = blkg_to_tg(blkg);
260    int cpu;
261
262    if (tg->stats_cpu == NULL)
263        return;
264
265    for_each_possible_cpu(cpu) {
266        struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
267
268        blkg_rwstat_reset(&sc->service_bytes);
269        blkg_rwstat_reset(&sc->serviced);
270    }
271}
272
273static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
274                       struct blkcg *blkcg)
275{
276    /*
277     * This is the common case when there are no blkcgs. Avoid lookup
278     * in this case
279     */
280    if (blkcg == &blkcg_root)
281        return td_root_tg(td);
282
283    return blkg_to_tg(blkg_lookup(blkcg, td->queue));
284}
285
286static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td,
287                          struct blkcg *blkcg)
288{
289    struct request_queue *q = td->queue;
290    struct throtl_grp *tg = NULL;
291
292    /*
293     * This is the common case when there are no blkcgs. Avoid lookup
294     * in this case
295     */
296    if (blkcg == &blkcg_root) {
297        tg = td_root_tg(td);
298    } else {
299        struct blkcg_gq *blkg;
300
301        blkg = blkg_lookup_create(blkcg, q);
302
303        /* if %NULL and @q is alive, fall back to root_tg */
304        if (!IS_ERR(blkg))
305            tg = blkg_to_tg(blkg);
306        else if (!blk_queue_dead(q))
307            tg = td_root_tg(td);
308    }
309
310    return tg;
311}
312
313static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
314{
315    /* Service tree is empty */
316    if (!root->count)
317        return NULL;
318
319    if (!root->left)
320        root->left = rb_first(&root->rb);
321
322    if (root->left)
323        return rb_entry_tg(root->left);
324
325    return NULL;
326}
327
328static void rb_erase_init(struct rb_node *n, struct rb_root *root)
329{
330    rb_erase(n, root);
331    RB_CLEAR_NODE(n);
332}
333
334static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root)
335{
336    if (root->left == n)
337        root->left = NULL;
338    rb_erase_init(n, &root->rb);
339    --root->count;
340}
341
342static void update_min_dispatch_time(struct throtl_rb_root *st)
343{
344    struct throtl_grp *tg;
345
346    tg = throtl_rb_first(st);
347    if (!tg)
348        return;
349
350    st->min_disptime = tg->disptime;
351}
352
353static void
354tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
355{
356    struct rb_node **node = &st->rb.rb_node;
357    struct rb_node *parent = NULL;
358    struct throtl_grp *__tg;
359    unsigned long key = tg->disptime;
360    int left = 1;
361
362    while (*node != NULL) {
363        parent = *node;
364        __tg = rb_entry_tg(parent);
365
366        if (time_before(key, __tg->disptime))
367            node = &parent->rb_left;
368        else {
369            node = &parent->rb_right;
370            left = 0;
371        }
372    }
373
374    if (left)
375        st->left = &tg->rb_node;
376
377    rb_link_node(&tg->rb_node, parent, node);
378    rb_insert_color(&tg->rb_node, &st->rb);
379}
380
381static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
382{
383    struct throtl_rb_root *st = &td->tg_service_tree;
384
385    tg_service_tree_add(st, tg);
386    throtl_mark_tg_on_rr(tg);
387    st->count++;
388}
389
390static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
391{
392    if (!throtl_tg_on_rr(tg))
393        __throtl_enqueue_tg(td, tg);
394}
395
396static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
397{
398    throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
399    throtl_clear_tg_on_rr(tg);
400}
401
402static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
403{
404    if (throtl_tg_on_rr(tg))
405        __throtl_dequeue_tg(td, tg);
406}
407
408static void throtl_schedule_next_dispatch(struct throtl_data *td)
409{
410    struct throtl_rb_root *st = &td->tg_service_tree;
411
412    /*
413     * If there are more bios pending, schedule more work.
414     */
415    if (!total_nr_queued(td))
416        return;
417
418    BUG_ON(!st->count);
419
420    update_min_dispatch_time(st);
421
422    if (time_before_eq(st->min_disptime, jiffies))
423        throtl_schedule_delayed_work(td, 0);
424    else
425        throtl_schedule_delayed_work(td, (st->min_disptime - jiffies));
426}
427
428static inline void
429throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
430{
431    tg->bytes_disp[rw] = 0;
432    tg->io_disp[rw] = 0;
433    tg->slice_start[rw] = jiffies;
434    tg->slice_end[rw] = jiffies + throtl_slice;
435    throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu",
436            rw == READ ? 'R' : 'W', tg->slice_start[rw],
437            tg->slice_end[rw], jiffies);
438}
439
440static inline void throtl_set_slice_end(struct throtl_data *td,
441        struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
442{
443    tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
444}
445
446static inline void throtl_extend_slice(struct throtl_data *td,
447        struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
448{
449    tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
450    throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu",
451            rw == READ ? 'R' : 'W', tg->slice_start[rw],
452            tg->slice_end[rw], jiffies);
453}
454
455/* Determine if previously allocated or extended slice is complete or not */
456static bool
457throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw)
458{
459    if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
460        return 0;
461
462    return 1;
463}
464
465/* Trim the used slices and adjust slice start accordingly */
466static inline void
467throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
468{
469    unsigned long nr_slices, time_elapsed, io_trim;
470    u64 bytes_trim, tmp;
471
472    BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
473
474    /*
475     * If bps are unlimited (-1), then time slice don't get
476     * renewed. Don't try to trim the slice if slice is used. A new
477     * slice will start when appropriate.
478     */
479    if (throtl_slice_used(td, tg, rw))
480        return;
481
482    /*
483     * A bio has been dispatched. Also adjust slice_end. It might happen
484     * that initially cgroup limit was very low resulting in high
485     * slice_end, but later limit was bumped up and bio was dispached
486     * sooner, then we need to reduce slice_end. A high bogus slice_end
487     * is bad because it does not allow new slice to start.
488     */
489
490    throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice);
491
492    time_elapsed = jiffies - tg->slice_start[rw];
493
494    nr_slices = time_elapsed / throtl_slice;
495
496    if (!nr_slices)
497        return;
498    tmp = tg->bps[rw] * throtl_slice * nr_slices;
499    do_div(tmp, HZ);
500    bytes_trim = tmp;
501
502    io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ;
503
504    if (!bytes_trim && !io_trim)
505        return;
506
507    if (tg->bytes_disp[rw] >= bytes_trim)
508        tg->bytes_disp[rw] -= bytes_trim;
509    else
510        tg->bytes_disp[rw] = 0;
511
512    if (tg->io_disp[rw] >= io_trim)
513        tg->io_disp[rw] -= io_trim;
514    else
515        tg->io_disp[rw] = 0;
516
517    tg->slice_start[rw] += nr_slices * throtl_slice;
518
519    throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu"
520            " start=%lu end=%lu jiffies=%lu",
521            rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim,
522            tg->slice_start[rw], tg->slice_end[rw], jiffies);
523}
524
525static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
526        struct bio *bio, unsigned long *wait)
527{
528    bool rw = bio_data_dir(bio);
529    unsigned int io_allowed;
530    unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
531    u64 tmp;
532
533    jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
534
535    /* Slice has just started. Consider one slice interval */
536    if (!jiffy_elapsed)
537        jiffy_elapsed_rnd = throtl_slice;
538
539    jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
540
541    /*
542     * jiffy_elapsed_rnd should not be a big value as minimum iops can be
543     * 1 then at max jiffy elapsed should be equivalent of 1 second as we
544     * will allow dispatch after 1 second and after that slice should
545     * have been trimmed.
546     */
547
548    tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
549    do_div(tmp, HZ);
550
551    if (tmp > UINT_MAX)
552        io_allowed = UINT_MAX;
553    else
554        io_allowed = tmp;
555
556    if (tg->io_disp[rw] + 1 <= io_allowed) {
557        if (wait)
558            *wait = 0;
559        return 1;
560    }
561
562    /* Calc approx time to dispatch */
563    jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
564
565    if (jiffy_wait > jiffy_elapsed)
566        jiffy_wait = jiffy_wait - jiffy_elapsed;
567    else
568        jiffy_wait = 1;
569
570    if (wait)
571        *wait = jiffy_wait;
572    return 0;
573}
574
575static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
576        struct bio *bio, unsigned long *wait)
577{
578    bool rw = bio_data_dir(bio);
579    u64 bytes_allowed, extra_bytes, tmp;
580    unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
581
582    jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
583
584    /* Slice has just started. Consider one slice interval */
585    if (!jiffy_elapsed)
586        jiffy_elapsed_rnd = throtl_slice;
587
588    jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
589
590    tmp = tg->bps[rw] * jiffy_elapsed_rnd;
591    do_div(tmp, HZ);
592    bytes_allowed = tmp;
593
594    if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
595        if (wait)
596            *wait = 0;
597        return 1;
598    }
599
600    /* Calc approx time to dispatch */
601    extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
602    jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]);
603
604    if (!jiffy_wait)
605        jiffy_wait = 1;
606
607    /*
608     * This wait time is without taking into consideration the rounding
609     * up we did. Add that time also.
610     */
611    jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
612    if (wait)
613        *wait = jiffy_wait;
614    return 0;
615}
616
617static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
618    if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
619        return 1;
620    return 0;
621}
622
623/*
624 * Returns whether one can dispatch a bio or not. Also returns approx number
625 * of jiffies to wait before this bio is with-in IO rate and can be dispatched
626 */
627static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
628                struct bio *bio, unsigned long *wait)
629{
630    bool rw = bio_data_dir(bio);
631    unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
632
633    /*
634      * Currently whole state machine of group depends on first bio
635     * queued in the group bio list. So one should not be calling
636     * this function with a different bio if there are other bios
637     * queued.
638     */
639    BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
640
641    /* If tg->bps = -1, then BW is unlimited */
642    if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
643        if (wait)
644            *wait = 0;
645        return 1;
646    }
647
648    /*
649     * If previous slice expired, start a new one otherwise renew/extend
650     * existing slice to make sure it is at least throtl_slice interval
651     * long since now.
652     */
653    if (throtl_slice_used(td, tg, rw))
654        throtl_start_new_slice(td, tg, rw);
655    else {
656        if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
657            throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
658    }
659
660    if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
661        && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
662        if (wait)
663            *wait = 0;
664        return 1;
665    }
666
667    max_wait = max(bps_wait, iops_wait);
668
669    if (wait)
670        *wait = max_wait;
671
672    if (time_before(tg->slice_end[rw], jiffies + max_wait))
673        throtl_extend_slice(td, tg, rw, jiffies + max_wait);
674
675    return 0;
676}
677
678static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
679                     int rw)
680{
681    struct throtl_grp *tg = blkg_to_tg(blkg);
682    struct tg_stats_cpu *stats_cpu;
683    unsigned long flags;
684
685    /* If per cpu stats are not allocated yet, don't do any accounting. */
686    if (tg->stats_cpu == NULL)
687        return;
688
689    /*
690     * Disabling interrupts to provide mutual exclusion between two
691     * writes on same cpu. It probably is not needed for 64bit. Not
692     * optimizing that case yet.
693     */
694    local_irq_save(flags);
695
696    stats_cpu = this_cpu_ptr(tg->stats_cpu);
697
698    blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
699    blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
700
701    local_irq_restore(flags);
702}
703
704static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
705{
706    bool rw = bio_data_dir(bio);
707
708    /* Charge the bio to the group */
709    tg->bytes_disp[rw] += bio->bi_size;
710    tg->io_disp[rw]++;
711
712    throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw);
713}
714
715static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
716            struct bio *bio)
717{
718    bool rw = bio_data_dir(bio);
719
720    bio_list_add(&tg->bio_lists[rw], bio);
721    /* Take a bio reference on tg */
722    blkg_get(tg_to_blkg(tg));
723    tg->nr_queued[rw]++;
724    td->nr_queued[rw]++;
725    throtl_enqueue_tg(td, tg);
726}
727
728static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
729{
730    unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
731    struct bio *bio;
732
733    if ((bio = bio_list_peek(&tg->bio_lists[READ])))
734        tg_may_dispatch(td, tg, bio, &read_wait);
735
736    if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
737        tg_may_dispatch(td, tg, bio, &write_wait);
738
739    min_wait = min(read_wait, write_wait);
740    disptime = jiffies + min_wait;
741
742    /* Update dispatch time */
743    throtl_dequeue_tg(td, tg);
744    tg->disptime = disptime;
745    throtl_enqueue_tg(td, tg);
746}
747
748static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
749                bool rw, struct bio_list *bl)
750{
751    struct bio *bio;
752
753    bio = bio_list_pop(&tg->bio_lists[rw]);
754    tg->nr_queued[rw]--;
755    /* Drop bio reference on blkg */
756    blkg_put(tg_to_blkg(tg));
757
758    BUG_ON(td->nr_queued[rw] <= 0);
759    td->nr_queued[rw]--;
760
761    throtl_charge_bio(tg, bio);
762    bio_list_add(bl, bio);
763    bio->bi_rw |= REQ_THROTTLED;
764
765    throtl_trim_slice(td, tg, rw);
766}
767
768static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
769                struct bio_list *bl)
770{
771    unsigned int nr_reads = 0, nr_writes = 0;
772    unsigned int max_nr_reads = throtl_grp_quantum*3/4;
773    unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads;
774    struct bio *bio;
775
776    /* Try to dispatch 75% READS and 25% WRITES */
777
778    while ((bio = bio_list_peek(&tg->bio_lists[READ]))
779        && tg_may_dispatch(td, tg, bio, NULL)) {
780
781        tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
782        nr_reads++;
783
784        if (nr_reads >= max_nr_reads)
785            break;
786    }
787
788    while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
789        && tg_may_dispatch(td, tg, bio, NULL)) {
790
791        tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
792        nr_writes++;
793
794        if (nr_writes >= max_nr_writes)
795            break;
796    }
797
798    return nr_reads + nr_writes;
799}
800
801static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
802{
803    unsigned int nr_disp = 0;
804    struct throtl_grp *tg;
805    struct throtl_rb_root *st = &td->tg_service_tree;
806
807    while (1) {
808        tg = throtl_rb_first(st);
809
810        if (!tg)
811            break;
812
813        if (time_before(jiffies, tg->disptime))
814            break;
815
816        throtl_dequeue_tg(td, tg);
817
818        nr_disp += throtl_dispatch_tg(td, tg, bl);
819
820        if (tg->nr_queued[0] || tg->nr_queued[1]) {
821            tg_update_disptime(td, tg);
822            throtl_enqueue_tg(td, tg);
823        }
824
825        if (nr_disp >= throtl_quantum)
826            break;
827    }
828
829    return nr_disp;
830}
831
832static void throtl_process_limit_change(struct throtl_data *td)
833{
834    struct request_queue *q = td->queue;
835    struct blkcg_gq *blkg, *n;
836
837    if (!td->limits_changed)
838        return;
839
840    xchg(&td->limits_changed, false);
841
842    throtl_log(td, "limits changed");
843
844    list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
845        struct throtl_grp *tg = blkg_to_tg(blkg);
846
847        if (!tg->limits_changed)
848            continue;
849
850        if (!xchg(&tg->limits_changed, false))
851            continue;
852
853        throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
854            " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE],
855            tg->iops[READ], tg->iops[WRITE]);
856
857        /*
858         * Restart the slices for both READ and WRITES. It
859         * might happen that a group's limit are dropped
860         * suddenly and we don't want to account recently
861         * dispatched IO with new low rate
862         */
863        throtl_start_new_slice(td, tg, 0);
864        throtl_start_new_slice(td, tg, 1);
865
866        if (throtl_tg_on_rr(tg))
867            tg_update_disptime(td, tg);
868    }
869}
870
871/* Dispatch throttled bios. Should be called without queue lock held. */
872static int throtl_dispatch(struct request_queue *q)
873{
874    struct throtl_data *td = q->td;
875    unsigned int nr_disp = 0;
876    struct bio_list bio_list_on_stack;
877    struct bio *bio;
878    struct blk_plug plug;
879
880    spin_lock_irq(q->queue_lock);
881
882    throtl_process_limit_change(td);
883
884    if (!total_nr_queued(td))
885        goto out;
886
887    bio_list_init(&bio_list_on_stack);
888
889    throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
890            total_nr_queued(td), td->nr_queued[READ],
891            td->nr_queued[WRITE]);
892
893    nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
894
895    if (nr_disp)
896        throtl_log(td, "bios disp=%u", nr_disp);
897
898    throtl_schedule_next_dispatch(td);
899out:
900    spin_unlock_irq(q->queue_lock);
901
902    /*
903     * If we dispatched some requests, unplug the queue to make sure
904     * immediate dispatch
905     */
906    if (nr_disp) {
907        blk_start_plug(&plug);
908        while((bio = bio_list_pop(&bio_list_on_stack)))
909            generic_make_request(bio);
910        blk_finish_plug(&plug);
911    }
912    return nr_disp;
913}
914
915void blk_throtl_work(struct work_struct *work)
916{
917    struct throtl_data *td = container_of(work, struct throtl_data,
918                    throtl_work.work);
919    struct request_queue *q = td->queue;
920
921    throtl_dispatch(q);
922}
923
924/* Call with queue lock held */
925static void
926throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
927{
928
929    struct delayed_work *dwork = &td->throtl_work;
930
931    /* schedule work if limits changed even if no bio is queued */
932    if (total_nr_queued(td) || td->limits_changed) {
933        /*
934         * We might have a work scheduled to be executed in future.
935         * Cancel that and schedule a new one.
936         */
937        __cancel_delayed_work(dwork);
938        queue_delayed_work(kthrotld_workqueue, dwork, delay);
939        throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
940                delay, jiffies);
941    }
942}
943
944static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
945                struct blkg_policy_data *pd, int off)
946{
947    struct throtl_grp *tg = pd_to_tg(pd);
948    struct blkg_rwstat rwstat = { }, tmp;
949    int i, cpu;
950
951    for_each_possible_cpu(cpu) {
952        struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
953
954        tmp = blkg_rwstat_read((void *)sc + off);
955        for (i = 0; i < BLKG_RWSTAT_NR; i++)
956            rwstat.cnt[i] += tmp.cnt[i];
957    }
958
959    return __blkg_prfill_rwstat(sf, pd, &rwstat);
960}
961
962static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
963                   struct seq_file *sf)
964{
965    struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
966
967    blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl,
968              cft->private, true);
969    return 0;
970}
971
972static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
973                  int off)
974{
975    struct throtl_grp *tg = pd_to_tg(pd);
976    u64 v = *(u64 *)((void *)tg + off);
977
978    if (v == -1)
979        return 0;
980    return __blkg_prfill_u64(sf, pd, v);
981}
982
983static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
984                   int off)
985{
986    struct throtl_grp *tg = pd_to_tg(pd);
987    unsigned int v = *(unsigned int *)((void *)tg + off);
988
989    if (v == -1)
990        return 0;
991    return __blkg_prfill_u64(sf, pd, v);
992}
993
994static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft,
995                 struct seq_file *sf)
996{
997    blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_u64,
998              &blkcg_policy_throtl, cft->private, false);
999    return 0;
1000}
1001
1002static int tg_print_conf_uint(struct cgroup *cgrp, struct cftype *cft,
1003                  struct seq_file *sf)
1004{
1005    blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_uint,
1006              &blkcg_policy_throtl, cft->private, false);
1007    return 0;
1008}
1009
1010static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf,
1011               bool is_u64)
1012{
1013    struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1014    struct blkg_conf_ctx ctx;
1015    struct throtl_grp *tg;
1016    struct throtl_data *td;
1017    int ret;
1018
1019    ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
1020    if (ret)
1021        return ret;
1022
1023    tg = blkg_to_tg(ctx.blkg);
1024    td = ctx.blkg->q->td;
1025
1026    if (!ctx.v)
1027        ctx.v = -1;
1028
1029    if (is_u64)
1030        *(u64 *)((void *)tg + cft->private) = ctx.v;
1031    else
1032        *(unsigned int *)((void *)tg + cft->private) = ctx.v;
1033
1034    /* XXX: we don't need the following deferred processing */
1035    xchg(&tg->limits_changed, true);
1036    xchg(&td->limits_changed, true);
1037    throtl_schedule_delayed_work(td, 0);
1038
1039    blkg_conf_finish(&ctx);
1040    return 0;
1041}
1042
1043static int tg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft,
1044               const char *buf)
1045{
1046    return tg_set_conf(cgrp, cft, buf, true);
1047}
1048
1049static int tg_set_conf_uint(struct cgroup *cgrp, struct cftype *cft,
1050                const char *buf)
1051{
1052    return tg_set_conf(cgrp, cft, buf, false);
1053}
1054
1055static struct cftype throtl_files[] = {
1056    {
1057        .name = "throttle.read_bps_device",
1058        .private = offsetof(struct throtl_grp, bps[READ]),
1059        .read_seq_string = tg_print_conf_u64,
1060        .write_string = tg_set_conf_u64,
1061        .max_write_len = 256,
1062    },
1063    {
1064        .name = "throttle.write_bps_device",
1065        .private = offsetof(struct throtl_grp, bps[WRITE]),
1066        .read_seq_string = tg_print_conf_u64,
1067        .write_string = tg_set_conf_u64,
1068        .max_write_len = 256,
1069    },
1070    {
1071        .name = "throttle.read_iops_device",
1072        .private = offsetof(struct throtl_grp, iops[READ]),
1073        .read_seq_string = tg_print_conf_uint,
1074        .write_string = tg_set_conf_uint,
1075        .max_write_len = 256,
1076    },
1077    {
1078        .name = "throttle.write_iops_device",
1079        .private = offsetof(struct throtl_grp, iops[WRITE]),
1080        .read_seq_string = tg_print_conf_uint,
1081        .write_string = tg_set_conf_uint,
1082        .max_write_len = 256,
1083    },
1084    {
1085        .name = "throttle.io_service_bytes",
1086        .private = offsetof(struct tg_stats_cpu, service_bytes),
1087        .read_seq_string = tg_print_cpu_rwstat,
1088    },
1089    {
1090        .name = "throttle.io_serviced",
1091        .private = offsetof(struct tg_stats_cpu, serviced),
1092        .read_seq_string = tg_print_cpu_rwstat,
1093    },
1094    { } /* terminate */
1095};
1096
1097static void throtl_shutdown_wq(struct request_queue *q)
1098{
1099    struct throtl_data *td = q->td;
1100
1101    cancel_delayed_work_sync(&td->throtl_work);
1102}
1103
1104static struct blkcg_policy blkcg_policy_throtl = {
1105    .pd_size = sizeof(struct throtl_grp),
1106    .cftypes = throtl_files,
1107
1108    .pd_init_fn = throtl_pd_init,
1109    .pd_exit_fn = throtl_pd_exit,
1110    .pd_reset_stats_fn = throtl_pd_reset_stats,
1111};
1112
1113bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
1114{
1115    struct throtl_data *td = q->td;
1116    struct throtl_grp *tg;
1117    bool rw = bio_data_dir(bio), update_disptime = true;
1118    struct blkcg *blkcg;
1119    bool throttled = false;
1120
1121    if (bio->bi_rw & REQ_THROTTLED) {
1122        bio->bi_rw &= ~REQ_THROTTLED;
1123        goto out;
1124    }
1125
1126    /*
1127     * A throtl_grp pointer retrieved under rcu can be used to access
1128     * basic fields like stats and io rates. If a group has no rules,
1129     * just update the dispatch stats in lockless manner and return.
1130     */
1131    rcu_read_lock();
1132    blkcg = bio_blkcg(bio);
1133    tg = throtl_lookup_tg(td, blkcg);
1134    if (tg) {
1135        if (tg_no_rule_group(tg, rw)) {
1136            throtl_update_dispatch_stats(tg_to_blkg(tg),
1137                             bio->bi_size, bio->bi_rw);
1138            goto out_unlock_rcu;
1139        }
1140    }
1141
1142    /*
1143     * Either group has not been allocated yet or it is not an unlimited
1144     * IO group
1145     */
1146    spin_lock_irq(q->queue_lock);
1147    tg = throtl_lookup_create_tg(td, blkcg);
1148    if (unlikely(!tg))
1149        goto out_unlock;
1150
1151    if (tg->nr_queued[rw]) {
1152        /*
1153         * There is already another bio queued in same dir. No
1154         * need to update dispatch time.
1155         */
1156        update_disptime = false;
1157        goto queue_bio;
1158
1159    }
1160
1161    /* Bio is with-in rate limit of group */
1162    if (tg_may_dispatch(td, tg, bio, NULL)) {
1163        throtl_charge_bio(tg, bio);
1164
1165        /*
1166         * We need to trim slice even when bios are not being queued
1167         * otherwise it might happen that a bio is not queued for
1168         * a long time and slice keeps on extending and trim is not
1169         * called for a long time. Now if limits are reduced suddenly
1170         * we take into account all the IO dispatched so far at new
1171         * low rate and * newly queued IO gets a really long dispatch
1172         * time.
1173         *
1174         * So keep on trimming slice even if bio is not queued.
1175         */
1176        throtl_trim_slice(td, tg, rw);
1177        goto out_unlock;
1178    }
1179
1180queue_bio:
1181    throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu"
1182            " iodisp=%u iops=%u queued=%d/%d",
1183            rw == READ ? 'R' : 'W',
1184            tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
1185            tg->io_disp[rw], tg->iops[rw],
1186            tg->nr_queued[READ], tg->nr_queued[WRITE]);
1187
1188    bio_associate_current(bio);
1189    throtl_add_bio_tg(q->td, tg, bio);
1190    throttled = true;
1191
1192    if (update_disptime) {
1193        tg_update_disptime(td, tg);
1194        throtl_schedule_next_dispatch(td);
1195    }
1196
1197out_unlock:
1198    spin_unlock_irq(q->queue_lock);
1199out_unlock_rcu:
1200    rcu_read_unlock();
1201out:
1202    return throttled;
1203}
1204
1205/**
1206 * blk_throtl_drain - drain throttled bios
1207 * @q: request_queue to drain throttled bios for
1208 *
1209 * Dispatch all currently throttled bios on @q through ->make_request_fn().
1210 */
1211void blk_throtl_drain(struct request_queue *q)
1212    __releases(q->queue_lock) __acquires(q->queue_lock)
1213{
1214    struct throtl_data *td = q->td;
1215    struct throtl_rb_root *st = &td->tg_service_tree;
1216    struct throtl_grp *tg;
1217    struct bio_list bl;
1218    struct bio *bio;
1219
1220    queue_lockdep_assert_held(q);
1221
1222    bio_list_init(&bl);
1223
1224    while ((tg = throtl_rb_first(st))) {
1225        throtl_dequeue_tg(td, tg);
1226
1227        while ((bio = bio_list_peek(&tg->bio_lists[READ])))
1228            tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1229        while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
1230            tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl);
1231    }
1232    spin_unlock_irq(q->queue_lock);
1233
1234    while ((bio = bio_list_pop(&bl)))
1235        generic_make_request(bio);
1236
1237    spin_lock_irq(q->queue_lock);
1238}
1239
1240int blk_throtl_init(struct request_queue *q)
1241{
1242    struct throtl_data *td;
1243    int ret;
1244
1245    td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
1246    if (!td)
1247        return -ENOMEM;
1248
1249    td->tg_service_tree = THROTL_RB_ROOT;
1250    td->limits_changed = false;
1251    INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
1252
1253    q->td = td;
1254    td->queue = q;
1255
1256    /* activate policy */
1257    ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
1258    if (ret)
1259        kfree(td);
1260    return ret;
1261}
1262
1263void blk_throtl_exit(struct request_queue *q)
1264{
1265    BUG_ON(!q->td);
1266    throtl_shutdown_wq(q);
1267    blkcg_deactivate_policy(q, &blkcg_policy_throtl);
1268    kfree(q->td);
1269}
1270
1271static int __init throtl_init(void)
1272{
1273    kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
1274    if (!kthrotld_workqueue)
1275        panic("Failed to create kthrotld\n");
1276
1277    return blkcg_policy_register(&blkcg_policy_throtl);
1278}
1279
1280module_init(throtl_init);
1281

Archive Download this file



interactive