diff options
Diffstat (limited to 'block/blk-throttle.c')
| -rw-r--r-- | block/blk-throttle.c | 1064 |
1 files changed, 744 insertions, 320 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 31146225f3d..08a32dfd384 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -25,18 +25,61 @@ static struct blkcg_policy blkcg_policy_throtl; /* A workqueue to queue throttle related work */ static struct workqueue_struct *kthrotld_workqueue; -static void throtl_schedule_delayed_work(struct throtl_data *td, - unsigned long delay); - -struct throtl_rb_root { - struct rb_root rb; - struct rb_node *left; - unsigned int count; - unsigned long min_disptime; + +/* + * To implement hierarchical throttling, throtl_grps form a tree and bios + * are dispatched upwards level by level until they reach the top and get + * issued. When dispatching bios from the children and local group at each + * level, if the bios are dispatched into a single bio_list, there's a risk + * of a local or child group which can queue many bios at once filling up + * the list starving others. + * + * To avoid such starvation, dispatched bios are queued separately + * according to where they came from. When they are again dispatched to + * the parent, they're popped in round-robin order so that no single source + * hogs the dispatch window. + * + * throtl_qnode is used to keep the queued bios separated by their sources. + * Bios are queued to throtl_qnode which in turn is queued to + * throtl_service_queue and then dispatched in round-robin order. + * + * It's also used to track the reference counts on blkg's. A qnode always + * belongs to a throtl_grp and gets queued on itself or the parent, so + * incrementing the reference of the associated throtl_grp when a qnode is + * queued and decrementing when dequeued is enough to keep the whole blkg + * tree pinned while bios are in flight. + */ +struct throtl_qnode { + struct list_head node; /* service_queue->queued[] */ + struct bio_list bios; /* queued bios */ + struct throtl_grp *tg; /* tg this qnode belongs to */ }; -#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ - .count = 0, .min_disptime = 0} +struct throtl_service_queue { + struct throtl_service_queue *parent_sq; /* the parent service_queue */ + + /* + * Bios queued directly to this service_queue or dispatched from + * children throtl_grp's. + */ + struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */ + unsigned int nr_queued[2]; /* number of queued bios */ + + /* + * RB tree of active children throtl_grp's, which are sorted by + * their ->disptime. + */ + struct rb_root pending_tree; /* RB tree of active tgs */ + struct rb_node *first_pending; /* first node in the tree */ + unsigned int nr_pending; /* # queued in the tree */ + unsigned long first_pending_disptime; /* disptime of the first tg */ + struct timer_list pending_timer; /* fires on first_pending_disptime */ +}; + +enum tg_state_flags { + THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */ + THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */ +}; #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) @@ -52,9 +95,26 @@ struct throtl_grp { /* must be the first member */ struct blkg_policy_data pd; - /* active throtl group service_tree member */ + /* active throtl group service_queue member */ struct rb_node rb_node; + /* throtl_data this group belongs to */ + struct throtl_data *td; + + /* this group's service queue */ + struct throtl_service_queue service_queue; + + /* + * qnode_on_self is used when bios are directly queued to this + * throtl_grp so that local bios compete fairly with bios + * dispatched from children. qnode_on_parent is used when bios are + * dispatched from this throtl_grp into its parent and will compete + * with the sibling qnode_on_parents and the parent's + * qnode_on_self. + */ + struct throtl_qnode qnode_on_self[2]; + struct throtl_qnode qnode_on_parent[2]; + /* * Dispatch time in jiffies. This is the estimated time when group * will unthrottle and is ready to dispatch more bio. It is used as @@ -64,11 +124,8 @@ struct throtl_grp { unsigned int flags; - /* Two lists for READ and WRITE */ - struct bio_list bio_lists[2]; - - /* Number of queued bios on READ and WRITE lists */ - unsigned int nr_queued[2]; + /* are there any throtl rules between this group and td? */ + bool has_rules[2]; /* bytes per second rate limits */ uint64_t bps[2]; @@ -85,9 +142,6 @@ struct throtl_grp { unsigned long slice_start[2]; unsigned long slice_end[2]; - /* Some throttle limits got updated for the group */ - int limits_changed; - /* Per cpu stats pointer */ struct tg_stats_cpu __percpu *stats_cpu; @@ -98,7 +152,7 @@ struct throtl_grp { struct throtl_data { /* service tree for active throtl groups */ - struct throtl_rb_root tg_service_tree; + struct throtl_service_queue service_queue; struct request_queue *queue; @@ -111,9 +165,7 @@ struct throtl_data unsigned int nr_undestroyed_grps; /* Work for dispatching throttled bios */ - struct delayed_work throtl_work; - - int limits_changed; + struct work_struct dispatch_work; }; /* list and work item to allocate percpu group stats */ @@ -123,6 +175,8 @@ static LIST_HEAD(tg_stats_alloc_list); static void tg_stats_alloc_fn(struct work_struct *); static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn); +static void throtl_pending_timer_fn(unsigned long arg); + static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd) { return pd ? container_of(pd, struct throtl_grp, pd) : NULL; @@ -143,41 +197,65 @@ static inline struct throtl_grp *td_root_tg(struct throtl_data *td) return blkg_to_tg(td->queue->root_blkg); } -enum tg_state_flags { - THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ -}; - -#define THROTL_TG_FNS(name) \ -static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ -{ \ - (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ -} \ -static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ -{ \ - (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ -} \ -static inline int throtl_tg_##name(const struct throtl_grp *tg) \ -{ \ - return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ +/** + * sq_to_tg - return the throl_grp the specified service queue belongs to + * @sq: the throtl_service_queue of interest + * + * Return the throtl_grp @sq belongs to. If @sq is the top-level one + * embedded in throtl_data, %NULL is returned. + */ +static struct throtl_grp *sq_to_tg(struct throtl_service_queue *sq) +{ + if (sq && sq->parent_sq) + return container_of(sq, struct throtl_grp, service_queue); + else + return NULL; } -THROTL_TG_FNS(on_rr); +/** + * sq_to_td - return throtl_data the specified service queue belongs to + * @sq: the throtl_service_queue of interest + * + * A service_queue can be embeded in either a throtl_grp or throtl_data. + * Determine the associated throtl_data accordingly and return it. + */ +static struct throtl_data *sq_to_td(struct throtl_service_queue *sq) +{ + struct throtl_grp *tg = sq_to_tg(sq); -#define throtl_log_tg(td, tg, fmt, args...) do { \ - char __pbuf[128]; \ + if (tg) + return tg->td; + else + return container_of(sq, struct throtl_data, service_queue); +} + +/** + * throtl_log - log debug message via blktrace + * @sq: the service_queue being reported + * @fmt: printf format string + * @args: printf args + * + * The messages are prefixed with "throtl BLKG_NAME" if @sq belongs to a + * throtl_grp; otherwise, just "throtl". + * + * TODO: this should be made a function and name formatting should happen + * after testing whether blktrace is enabled. + */ +#define throtl_log(sq, fmt, args...) do { \ + struct throtl_grp *__tg = sq_to_tg((sq)); \ + struct throtl_data *__td = sq_to_td((sq)); \ + \ + (void)__td; \ + if ((__tg)) { \ + char __pbuf[128]; \ \ - blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf)); \ - blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \ + blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf)); \ + blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \ + } else { \ + blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \ + } \ } while (0) -#define throtl_log(td, fmt, args...) \ - blk_add_trace_msg((td)->queue, "throtl " fmt, ##args) - -static inline unsigned int total_nr_queued(struct throtl_data *td) -{ - return td->nr_queued[0] + td->nr_queued[1]; -} - /* * Worker for allocating per cpu stat for tgs. This is scheduled on the * system_wq once there are some groups on the alloc_list waiting for @@ -215,15 +293,141 @@ alloc_stats: goto alloc_stats; } +static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg) +{ + INIT_LIST_HEAD(&qn->node); + bio_list_init(&qn->bios); + qn->tg = tg; +} + +/** + * throtl_qnode_add_bio - add a bio to a throtl_qnode and activate it + * @bio: bio being added + * @qn: qnode to add bio to + * @queued: the service_queue->queued[] list @qn belongs to + * + * Add @bio to @qn and put @qn on @queued if it's not already on. + * @qn->tg's reference count is bumped when @qn is activated. See the + * comment on top of throtl_qnode definition for details. + */ +static void throtl_qnode_add_bio(struct bio *bio, struct throtl_qnode *qn, + struct list_head *queued) +{ + bio_list_add(&qn->bios, bio); + if (list_empty(&qn->node)) { + list_add_tail(&qn->node, queued); + blkg_get(tg_to_blkg(qn->tg)); + } +} + +/** + * throtl_peek_queued - peek the first bio on a qnode list + * @queued: the qnode list to peek + */ +static struct bio *throtl_peek_queued(struct list_head *queued) +{ + struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + bio = bio_list_peek(&qn->bios); + WARN_ON_ONCE(!bio); + return bio; +} + +/** + * throtl_pop_queued - pop the first bio form a qnode list + * @queued: the qnode list to pop a bio from + * @tg_to_put: optional out argument for throtl_grp to put + * + * Pop the first bio from the qnode list @queued. After popping, the first + * qnode is removed from @queued if empty or moved to the end of @queued so + * that the popping order is round-robin. + * + * When the first qnode is removed, its associated throtl_grp should be put + * too. If @tg_to_put is NULL, this function automatically puts it; + * otherwise, *@tg_to_put is set to the throtl_grp to put and the caller is + * responsible for putting it. + */ +static struct bio *throtl_pop_queued(struct list_head *queued, + struct throtl_grp **tg_to_put) +{ + struct throtl_qnode *qn = list_first_entry(queued, struct throtl_qnode, node); + struct bio *bio; + + if (list_empty(queued)) + return NULL; + + bio = bio_list_pop(&qn->bios); + WARN_ON_ONCE(!bio); + + if (bio_list_empty(&qn->bios)) { + list_del_init(&qn->node); + if (tg_to_put) + *tg_to_put = qn->tg; + else + blkg_put(tg_to_blkg(qn->tg)); + } else { + list_move_tail(&qn->node, queued); + } + + return bio; +} + +/* init a service_queue, assumes the caller zeroed it */ +static void throtl_service_queue_init(struct throtl_service_queue *sq, + struct throtl_service_queue *parent_sq) +{ + INIT_LIST_HEAD(&sq->queued[0]); + INIT_LIST_HEAD(&sq->queued[1]); + sq->pending_tree = RB_ROOT; + sq->parent_sq = parent_sq; + setup_timer(&sq->pending_timer, throtl_pending_timer_fn, + (unsigned long)sq); +} + +static void throtl_service_queue_exit(struct throtl_service_queue *sq) +{ + del_timer_sync(&sq->pending_timer); +} + static void throtl_pd_init(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); + struct throtl_data *td = blkg->q->td; + struct throtl_service_queue *parent_sq; unsigned long flags; + int rw; + + /* + * If sane_hierarchy is enabled, we switch to properly hierarchical + * behavior where limits on a given throtl_grp are applied to the + * whole subtree rather than just the group itself. e.g. If 16M + * read_bps limit is set on the root group, the whole system can't + * exceed 16M for the device. + * + * If sane_hierarchy is not enabled, the broken flat hierarchy + * behavior is retained where all throtl_grps are treated as if + * they're all separate root groups right below throtl_data. + * Limits of a group don't interact with limits of other groups + * regardless of the position of the group in the hierarchy. + */ + parent_sq = &td->service_queue; + + if (cgroup_sane_behavior(blkg->blkcg->css.cgroup) && blkg->parent) + parent_sq = &blkg_to_tg(blkg->parent)->service_queue; + + throtl_service_queue_init(&tg->service_queue, parent_sq); + + for (rw = READ; rw <= WRITE; rw++) { + throtl_qnode_init(&tg->qnode_on_self[rw], tg); + throtl_qnode_init(&tg->qnode_on_parent[rw], tg); + } RB_CLEAR_NODE(&tg->rb_node); - bio_list_init(&tg->bio_lists[0]); - bio_list_init(&tg->bio_lists[1]); - tg->limits_changed = false; + tg->td = td; tg->bps[READ] = -1; tg->bps[WRITE] = -1; @@ -241,6 +445,30 @@ static void throtl_pd_init(struct blkcg_gq *blkg) spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); } +/* + * Set has_rules[] if @tg or any of its parents have limits configured. + * This doesn't require walking up to the top of the hierarchy as the + * parent's has_rules[] is guaranteed to be correct. + */ +static void tg_update_has_rules(struct throtl_grp *tg) +{ + struct throtl_grp *parent_tg = sq_to_tg(tg->service_queue.parent_sq); + int rw; + + for (rw = READ; rw <= WRITE; rw++) + tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) || + (tg->bps[rw] != -1 || tg->iops[rw] != -1); +} + +static void throtl_pd_online(struct blkcg_gq *blkg) +{ + /* + * We don't want new groups to escape the limits of its ancestors. + * Update has_rules[] after a new group is brought online. + */ + tg_update_has_rules(blkg_to_tg(blkg)); +} + static void throtl_pd_exit(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); @@ -251,6 +479,8 @@ static void throtl_pd_exit(struct blkcg_gq *blkg) spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); free_percpu(tg->stats_cpu); + + throtl_service_queue_exit(&tg->service_queue); } static void throtl_pd_reset_stats(struct blkcg_gq *blkg) @@ -309,17 +539,18 @@ static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, return tg; } -static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) +static struct throtl_grp * +throtl_rb_first(struct throtl_service_queue *parent_sq) { /* Service tree is empty */ - if (!root->count) + if (!parent_sq->nr_pending) return NULL; - if (!root->left) - root->left = rb_first(&root->rb); + if (!parent_sq->first_pending) + parent_sq->first_pending = rb_first(&parent_sq->pending_tree); - if (root->left) - return rb_entry_tg(root->left); + if (parent_sq->first_pending) + return rb_entry_tg(parent_sq->first_pending); return NULL; } @@ -330,29 +561,30 @@ static void rb_erase_init(struct rb_node *n, struct rb_root *root) RB_CLEAR_NODE(n); } -static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root) +static void throtl_rb_erase(struct rb_node *n, + struct throtl_service_queue *parent_sq) { - if (root->left == n) - root->left = NULL; - rb_erase_init(n, &root->rb); - --root->count; + if (parent_sq->first_pending == n) + parent_sq->first_pending = NULL; + rb_erase_init(n, &parent_sq->pending_tree); + --parent_sq->nr_pending; } -static void update_min_dispatch_time(struct throtl_rb_root *st) +static void update_min_dispatch_time(struct throtl_service_queue *parent_sq) { struct throtl_grp *tg; - tg = throtl_rb_first(st); + tg = throtl_rb_first(parent_sq); if (!tg) return; - st->min_disptime = tg->disptime; + parent_sq->first_pending_disptime = tg->disptime; } -static void -tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) +static void tg_service_queue_add(struct throtl_grp *tg) { - struct rb_node **node = &st->rb.rb_node; + struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq; + struct rb_node **node = &parent_sq->pending_tree.rb_node; struct rb_node *parent = NULL; struct throtl_grp *__tg; unsigned long key = tg->disptime; @@ -371,89 +603,135 @@ tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) } if (left) - st->left = &tg->rb_node; + parent_sq->first_pending = &tg->rb_node; rb_link_node(&tg->rb_node, parent, node); - rb_insert_color(&tg->rb_node, &st->rb); + rb_insert_color(&tg->rb_node, &parent_sq->pending_tree); } -static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) +static void __throtl_enqueue_tg(struct throtl_grp *tg) { - struct throtl_rb_root *st = &td->tg_service_tree; + tg_service_queue_add(tg); + tg->flags |= THROTL_TG_PENDING; + tg->service_queue.parent_sq->nr_pending++; +} - tg_service_tree_add(st, tg); - throtl_mark_tg_on_rr(tg); - st->count++; +static void throtl_enqueue_tg(struct throtl_grp *tg) +{ + if (!(tg->flags & THROTL_TG_PENDING)) + __throtl_enqueue_tg(tg); } -static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) +static void __throtl_dequeue_tg(struct throtl_grp *tg) { - if (!throtl_tg_on_rr(tg)) - __throtl_enqueue_tg(td, tg); + throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq); + tg->flags &= ~THROTL_TG_PENDING; } -static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) +static void throtl_dequeue_tg(struct throtl_grp *tg) { - throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); - throtl_clear_tg_on_rr(tg); + if (tg->flags & THROTL_TG_PENDING) + __throtl_dequeue_tg(tg); } -static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) +/* Call with queue lock held */ +static void throtl_schedule_pending_timer(struct throtl_service_queue *sq, + unsigned long expires) { - if (throtl_tg_on_rr(tg)) - __throtl_dequeue_tg(td, tg); + mod_timer(&sq->pending_timer, expires); + throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu", + expires - jiffies, jiffies); } -static void throtl_schedule_next_dispatch(struct throtl_data *td) +/** + * throtl_schedule_next_dispatch - schedule the next dispatch cycle + * @sq: the service_queue to schedule dispatch for + * @force: force scheduling + * + * Arm @sq->pending_timer so that the next dispatch cycle starts on the + * dispatch time of the first pending child. Returns %true if either timer + * is armed or there's no pending child left. %false if the current + * dispatch window is still open and the caller should continue + * dispatching. + * + * If @force is %true, the dispatch timer is always scheduled and this + * function is guaranteed to return %true. This is to be used when the + * caller can't dispatch itself and needs to invoke pending_timer + * unconditionally. Note that forced scheduling is likely to induce short + * delay before dispatch starts even if @sq->first_pending_disptime is not + * in the future and thus shouldn't be used in hot paths. + */ +static bool throtl_schedule_next_dispatch(struct throtl_service_queue *sq, + bool force) { - struct throtl_rb_root *st = &td->tg_service_tree; + /* any pending children left? */ + if (!sq->nr_pending) + return true; - /* - * If there are more bios pending, schedule more work. - */ - if (!total_nr_queued(td)) - return; + update_min_dispatch_time(sq); - BUG_ON(!st->count); + /* is the next dispatch time in the future? */ + if (force || time_after(sq->first_pending_disptime, jiffies)) { + throtl_schedule_pending_timer(sq, sq->first_pending_disptime); + return true; + } - update_min_dispatch_time(st); + /* tell the caller to continue dispatching */ + return false; +} - if (time_before_eq(st->min_disptime, jiffies)) - throtl_schedule_delayed_work(td, 0); - else - throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); +static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, + bool rw, unsigned long start) +{ + tg->bytes_disp[rw] = 0; + tg->io_disp[rw] = 0; + + /* + * Previous slice has expired. We must have trimmed it after last + * bio dispatch. That means since start of last slice, we never used + * that bandwidth. Do try to make use of that bandwidth while giving + * credit. + */ + if (time_after_eq(start, tg->slice_start[rw])) + tg->slice_start[rw] = start; + + tg->slice_end[rw] = jiffies + throtl_slice; + throtl_log(&tg->service_queue, + "[%c] new slice with credit start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); } -static inline void -throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) +static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw) { tg->bytes_disp[rw] = 0; tg->io_disp[rw] = 0; tg->slice_start[rw] = jiffies; tg->slice_end[rw] = jiffies + throtl_slice; - throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu", - rw == READ ? 'R' : 'W', tg->slice_start[rw], - tg->slice_end[rw], jiffies); + throtl_log(&tg->service_queue, + "[%c] new slice start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); } -static inline void throtl_set_slice_end(struct throtl_data *td, - struct throtl_grp *tg, bool rw, unsigned long jiffy_end) +static inline void throtl_set_slice_end(struct throtl_grp *tg, bool rw, + unsigned long jiffy_end) { tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); } -static inline void throtl_extend_slice(struct throtl_data *td, - struct throtl_grp *tg, bool rw, unsigned long jiffy_end) +static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw, + unsigned long jiffy_end) { tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); - throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu", - rw == READ ? 'R' : 'W', tg->slice_start[rw], - tg->slice_end[rw], jiffies); + throtl_log(&tg->service_queue, + "[%c] extend slice start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', tg->slice_start[rw], + tg->slice_end[rw], jiffies); } /* Determine if previously allocated or extended slice is complete or not */ -static bool -throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) +static bool throtl_slice_used(struct throtl_grp *tg, bool rw) { if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) return 0; @@ -462,8 +740,7 @@ throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) } /* Trim the used slices and adjust slice start accordingly */ -static inline void -throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) +static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw) { unsigned long nr_slices, time_elapsed, io_trim; u64 bytes_trim, tmp; @@ -475,7 +752,7 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) * renewed. Don't try to trim the slice if slice is used. A new * slice will start when appropriate. */ - if (throtl_slice_used(td, tg, rw)) + if (throtl_slice_used(tg, rw)) return; /* @@ -486,7 +763,7 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) * is bad because it does not allow new slice to start. */ - throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice); + throtl_set_slice_end(tg, rw, jiffies + throtl_slice); time_elapsed = jiffies - tg->slice_start[rw]; @@ -515,14 +792,14 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) tg->slice_start[rw] += nr_slices * throtl_slice; - throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu" - " start=%lu end=%lu jiffies=%lu", - rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, - tg->slice_start[rw], tg->slice_end[rw], jiffies); + throtl_log(&tg->service_queue, + "[%c] trim slice nr=%lu bytes=%llu io=%lu start=%lu end=%lu jiffies=%lu", + rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, + tg->slice_start[rw], tg->slice_end[rw], jiffies); } -static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, - struct bio *bio, unsigned long *wait) +static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) { bool rw = bio_data_dir(bio); unsigned int io_allowed; @@ -571,8 +848,8 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, return 0; } -static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, - struct bio *bio, unsigned long *wait) +static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) { bool rw = bio_data_dir(bio); u64 bytes_allowed, extra_bytes, tmp; @@ -613,18 +890,12 @@ static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, return 0; } -static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) { - if (tg->bps[rw] == -1 && tg->iops[rw] == -1) - return 1; - return 0; -} - /* * Returns whether one can dispatch a bio or not. Also returns approx number * of jiffies to wait before this bio is with-in IO rate and can be dispatched */ -static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, - struct bio *bio, unsigned long *wait) +static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, + unsigned long *wait) { bool rw = bio_data_dir(bio); unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; @@ -635,7 +906,8 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, * this function with a different bio if there are other bios * queued. */ - BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); + BUG_ON(tg->service_queue.nr_queued[rw] && + bio != throtl_peek_queued(&tg->service_queue.queued[rw])); /* If tg->bps = -1, then BW is unlimited */ if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { @@ -649,15 +921,15 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, * existing slice to make sure it is at least throtl_slice interval * long since now. */ - if (throtl_slice_used(td, tg, rw)) - throtl_start_new_slice(td, tg, rw); + if (throtl_slice_used(tg, rw)) + throtl_start_new_slice(tg, rw); else { if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) - throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); + throtl_extend_slice(tg, rw, jiffies + throtl_slice); } - if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) - && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) { + if (tg_with_in_bps_limit(tg, bio, &bps_wait) && + tg_with_in_iops_limit(tg, bio, &iops_wait)) { if (wait) *wait = 0; return 1; @@ -669,7 +941,7 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, *wait = max_wait; if (time_before(tg->slice_end[rw], jiffies + max_wait)) - throtl_extend_slice(td, tg, rw, jiffies + max_wait); + throtl_extend_slice(tg, rw, jiffies + max_wait); return 0; } @@ -708,65 +980,136 @@ static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) tg->bytes_disp[rw] += bio->bi_size; tg->io_disp[rw]++; - throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw); + /* + * REQ_THROTTLED is used to prevent the same bio to be throttled + * more than once as a throttled bio will go through blk-throtl the + * second time when it eventually gets issued. Set it when a bio + * is being charged to a tg. + * + * Dispatch stats aren't recursive and each @bio should only be + * accounted by the @tg it was originally associated with. Let's + * update the stats when setting REQ_THROTTLED for the first time + * which is guaranteed to be for the @bio's original tg. + */ + if (!(bio->bi_rw & REQ_THROTTLED)) { + bio->bi_rw |= REQ_THROTTLED; + throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, + bio->bi_rw); + } } -static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, - struct bio *bio) +/** + * throtl_add_bio_tg - add a bio to the specified throtl_grp + * @bio: bio to add + * @qn: qnode to use + * @tg: the target throtl_grp + * + * Add @bio to @tg's service_queue using @qn. If @qn is not specified, + * tg->qnode_on_self[] is used. + */ +static void throtl_add_bio_tg(struct bio *bio, struct throtl_qnode *qn, + struct throtl_grp *tg) { + struct throtl_service_queue *sq = &tg->service_queue; bool rw = bio_data_dir(bio); - bio_list_add(&tg->bio_lists[rw], bio); - /* Take a bio reference on tg */ - blkg_get(tg_to_blkg(tg)); - tg->nr_queued[rw]++; - td->nr_queued[rw]++; - throtl_enqueue_tg(td, tg); + if (!qn) + qn = &tg->qnode_on_self[rw]; + + /* + * If @tg doesn't currently have any bios queued in the same + * direction, queueing @bio can change when @tg should be + * dispatched. Mark that @tg was empty. This is automatically + * cleaered on the next tg_update_disptime(). + */ + if (!sq->nr_queued[rw]) + tg->flags |= THROTL_TG_WAS_EMPTY; + + throtl_qnode_add_bio(bio, qn, &sq->queued[rw]); + + sq->nr_queued[rw]++; + throtl_enqueue_tg(tg); } -static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) +static void tg_update_disptime(struct throtl_grp *tg) { + struct throtl_service_queue *sq = &tg->service_queue; unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; struct bio *bio; - if ((bio = bio_list_peek(&tg->bio_lists[READ]))) - tg_may_dispatch(td, tg, bio, &read_wait); + if ((bio = throtl_peek_queued(&sq->queued[READ]))) + tg_may_dispatch(tg, bio, &read_wait); - if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) - tg_may_dispatch(td, tg, bio, &write_wait); + if ((bio = throtl_peek_queued(&sq->queued[WRITE]))) + tg_may_dispatch(tg, bio, &write_wait); min_wait = min(read_wait, write_wait); disptime = jiffies + min_wait; /* Update dispatch time */ - throtl_dequeue_tg(td, tg); + throtl_dequeue_tg(tg); tg->disptime = disptime; - throtl_enqueue_tg(td, tg); + throtl_enqueue_tg(tg); + + /* see throtl_add_bio_tg() */ + tg->flags &= ~THROTL_TG_WAS_EMPTY; } -static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, - bool rw, struct bio_list *bl) +static void start_parent_slice_with_credit(struct throtl_grp *child_tg, + struct throtl_grp *parent_tg, bool rw) { - struct bio *bio; + if (throtl_slice_used(parent_tg, rw)) { + throtl_start_new_slice_with_credit(parent_tg, rw, + child_tg->slice_start[rw]); + } + +} - bio = bio_list_pop(&tg->bio_lists[rw]); - tg->nr_queued[rw]--; - /* Drop bio reference on blkg */ - blkg_put(tg_to_blkg(tg)); +static void tg_dispatch_one_bio(struct throtl_grp *tg, bool rw) +{ + struct throtl_service_queue *sq = &tg->service_queue; + struct throtl_service_queue *parent_sq = sq->parent_sq; + struct throtl_grp *parent_tg = sq_to_tg(parent_sq); + struct throtl_grp *tg_to_put = NULL; + struct bio *bio; - BUG_ON(td->nr_queued[rw] <= 0); - td->nr_queued[rw]--; + /* + * @bio is being transferred from @tg to @parent_sq. Popping a bio + * from @tg may put its reference and @parent_sq might end up + * getting released prematurely. Remember the tg to put and put it + * after @bio is transferred to @parent_sq. + */ + bio = throtl_pop_queued(&sq->queued[rw], &tg_to_put); + sq->nr_queued[rw]--; throtl_charge_bio(tg, bio); - bio_list_add(bl, bio); - bio->bi_rw |= REQ_THROTTLED; - throtl_trim_slice(td, tg, rw); + /* + * If our parent is another tg, we just need to transfer @bio to + * the parent using throtl_add_bio_tg(). If our parent is + * @td->service_queue, @bio is ready to be issued. Put it on its + * bio_lists[] and decrease total number queued. The caller is + * responsible for issuing these bios. + */ + if (parent_tg) { + throtl_add_bio_tg(bio, &tg->qnode_on_parent[rw], parent_tg); + start_parent_slice_with_credit(tg, parent_tg, rw); + } else { + throtl_qnode_add_bio(bio, &tg->qnode_on_parent[rw], + &parent_sq->queued[rw]); + BUG_ON(tg->td->nr_queued[rw] <= 0); + tg->td->nr_queued[rw]--; + } + + throtl_trim_slice(tg, rw); + + if (tg_to_put) + blkg_put(tg_to_blkg(tg_to_put)); } -static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, - struct bio_list *bl) +static int throtl_dispatch_tg(struct throtl_grp *tg) { + struct throtl_service_queue *sq = &tg->service_queue; unsigned int nr_reads = 0, nr_writes = 0; unsigned int max_nr_reads = throtl_grp_quantum*3/4; unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; @@ -774,20 +1117,20 @@ static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, /* Try to dispatch 75% READS and 25% WRITES */ - while ((bio = bio_list_peek(&tg->bio_lists[READ])) - && tg_may_dispatch(td, tg, bio, NULL)) { + while ((bio = throtl_peek_queued(&sq->queued[READ])) && + tg_may_dispatch(tg, bio, NULL)) { - tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); + tg_dispatch_one_bio(tg, bio_data_dir(bio)); nr_reads++; if (nr_reads >= max_nr_reads) break; } - while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) - && tg_may_dispatch(td, tg, bio, NULL)) { + while ((bio = throtl_peek_queued(&sq->queued[WRITE])) && + tg_may_dispatch(tg, bio, NULL)) { - tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); + tg_dispatch_one_bio(tg, bio_data_dir(bio)); nr_writes++; if (nr_writes >= max_nr_writes) @@ -797,14 +1140,13 @@ static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, return nr_reads + nr_writes; } -static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) +static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) { unsigned int nr_disp = 0; - struct throtl_grp *tg; - struct throtl_rb_root *st = &td->tg_service_tree; while (1) { - tg = throtl_rb_first(st); + struct throtl_grp *tg = throtl_rb_first(parent_sq); + struct throtl_service_queue *sq = &tg->service_queue; if (!tg) break; @@ -812,14 +1154,12 @@ static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) if (time_before(jiffies, tg->disptime)) break; - throtl_dequeue_tg(td, tg); + throtl_dequeue_tg(tg); - nr_disp += throtl_dispatch_tg(td, tg, bl); + nr_disp += throtl_dispatch_tg(tg); - if (tg->nr_queued[0] || tg->nr_queued[1]) { - tg_update_disptime(td, tg); - throtl_enqueue_tg(td, tg); - } + if (sq->nr_queued[0] || sq->nr_queued[1]) + tg_update_disptime(tg); if (nr_disp >= throtl_quantum) break; @@ -828,111 +1168,111 @@ static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) return nr_disp; } -static void throtl_process_limit_change(struct throtl_data *td) +/** + * throtl_pending_timer_fn - timer function for service_queue->pending_timer + * @arg: the throtl_service_queue being serviced + * + * This timer is armed when a child throtl_grp with active bio's become + * pending and queued on the service_queue's pending_tree and expires when + * the first child throtl_grp should be dispatched. This function + * dispatches bio's from the children throtl_grps to the parent + * service_queue. + * + * If the parent's parent is another throtl_grp, dispatching is propagated + * by either arming its pending_timer or repeating dispatch directly. If + * the top-level service_tree is reached, throtl_data->dispatch_work is + * kicked so that the ready bio's are issued. + */ +static void throtl_pending_timer_fn(unsigned long arg) { + struct throtl_service_queue *sq = (void *)arg; + struct throtl_grp *tg = sq_to_tg(sq); + struct throtl_data *td = sq_to_td(sq); struct request_queue *q = td->queue; - struct blkcg_gq *blkg, *n; - - if (!td->limits_changed) - return; - - xchg(&td->limits_changed, false); - - throtl_log(td, "limits changed"); - - list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) { - struct throtl_grp *tg = blkg_to_tg(blkg); + struct throtl_service_queue *parent_sq; + bool dispatched; + int ret; - if (!tg->limits_changed) - continue; + spin_lock_irq(q->queue_lock); +again: + parent_sq = sq->parent_sq; + dispatched = false; + + while (true) { + throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u", + sq->nr_queued[READ] + sq->nr_queued[WRITE], + sq->nr_queued[READ], sq->nr_queued[WRITE]); + + ret = throtl_select_dispatch(sq); + if (ret) { + throtl_log(sq, "bios disp=%u", ret); + dispatched = true; + } - if (!xchg(&tg->limits_changed, false)) - continue; + if (throtl_schedule_next_dispatch(sq, false)) + break; - throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" - " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], - tg->iops[READ], tg->iops[WRITE]); + /* this dispatch windows is still open, relax and repeat */ + spin_unlock_irq(q->queue_lock); + cpu_relax(); + spin_lock_irq(q->queue_lock); + } - /* - * Restart the slices for both READ and WRITES. It - * might happen that a group's limit are dropped - * suddenly and we don't want to account recently - * dispatched IO with new low rate - */ - throtl_start_new_slice(td, tg, 0); - throtl_start_new_slice(td, tg, 1); + if (!dispatched) + goto out_unlock; - if (throtl_tg_on_rr(tg)) - tg_update_disptime(td, tg); + if (parent_sq) { + /* @parent_sq is another throl_grp, propagate dispatch */ + if (tg->flags & THROTL_TG_WAS_EMPTY) { + tg_update_disptime(tg); + if (!throtl_schedule_next_dispatch(parent_sq, false)) { + /* window is already open, repeat dispatching */ + sq = parent_sq; + tg = sq_to_tg(sq); + goto again; + } + } + } else { + /* reached the top-level, queue issueing */ + queue_work(kthrotld_workqueue, &td->dispatch_work); } +out_unlock: + spin_unlock_irq(q->queue_lock); } -/* Dispatch throttled bios. Should be called without queue lock held. */ -static int throtl_dispatch(struct request_queue *q) +/** + * blk_throtl_dispatch_work_fn - work function for throtl_data->dispatch_work + * @work: work item being executed + * + * This function is queued for execution when bio's reach the bio_lists[] + * of throtl_data->service_queue. Those bio's are ready and issued by this + * function. + */ +void blk_throtl_dispatch_work_fn(struct work_struct *work) { - struct throtl_data *td = q->td; - unsigned int nr_disp = 0; + struct throtl_data *td = container_of(work, struct throtl_data, + dispatch_work); + struct throtl_service_queue *td_sq = &td->service_queue; + struct request_queue *q = td->queue; struct bio_list bio_list_on_stack; struct bio *bio; struct blk_plug plug; - - spin_lock_irq(q->queue_lock); - - throtl_process_limit_change(td); - - if (!total_nr_queued(td)) - goto out; + int rw; bio_list_init(&bio_list_on_stack); - throtl_log(td, "dispatch nr_queued=%u read=%u write=%u", - total_nr_queued(td), td->nr_queued[READ], - td->nr_queued[WRITE]); - - nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); - - if (nr_disp) - throtl_log(td, "bios disp=%u", nr_disp); - - throtl_schedule_next_dispatch(td); -out: + spin_lock_irq(q->queue_lock); + for (rw = READ; rw <= WRITE; rw++) + while ((bio = throtl_pop_queued(&td_sq->queued[rw], NULL))) + bio_list_add(&bio_list_on_stack, bio); spin_unlock_irq(q->queue_lock); - /* - * If we dispatched some requests, unplug the queue to make sure - * immediate dispatch - */ - if (nr_disp) { + if (!bio_list_empty(&bio_list_on_stack)) { blk_start_plug(&plug); while((bio = bio_list_pop(&bio_list_on_stack))) generic_make_request(bio); blk_finish_plug(&plug); } - return nr_disp; -} - -void blk_throtl_work(struct work_struct *work) -{ - struct throtl_data *td = container_of(work, struct throtl_data, - throtl_work.work); - struct request_queue *q = td->queue; - - throtl_dispatch(q); -} - -/* Call with queue lock held */ -static void -throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) -{ - - struct delayed_work *dwork = &td->throtl_work; - - /* schedule work if limits changed even if no bio is queued */ - if (total_nr_queued(td) || td->limits_changed) { - mod_delayed_work(kthrotld_workqueue, dwork, delay); - throtl_log(td, "schedule work. delay=%lu jiffies=%lu", - delay, jiffies); - } } static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, @@ -1007,7 +1347,9 @@ static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf, struct blkcg *blkcg = cgroup_to_blkcg(cgrp); struct blkg_conf_ctx ctx; struct throtl_grp *tg; - struct throtl_data *td; + struct throtl_service_queue *sq; + struct blkcg_gq *blkg; + struct cgroup *pos_cgrp; int ret; ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); @@ -1015,7 +1357,7 @@ static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf, return ret; tg = blkg_to_tg(ctx.blkg); - td = ctx.blkg->q->td; + sq = &tg->service_queue; if (!ctx.v) ctx.v = -1; @@ -1025,10 +1367,37 @@ static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf, else *(unsigned int *)((void *)tg + cft->private) = ctx.v; - /* XXX: we don't need the following deferred processing */ - xchg(&tg->limits_changed, true); - xchg(&td->limits_changed, true); - throtl_schedule_delayed_work(td, 0); + throtl_log(&tg->service_queue, + "limit change rbps=%llu wbps=%llu riops=%u wiops=%u", + tg->bps[READ], tg->bps[WRITE], + tg->iops[READ], tg->iops[WRITE]); + + /* + * Update has_rules[] flags for the updated tg's subtree. A tg is + * considered to have rules if either the tg itself or any of its + * ancestors has rules. This identifies groups without any + * restrictions in the whole hierarchy and allows them to bypass + * blk-throttle. + */ + tg_update_has_rules(tg); + blkg_for_each_descendant_pre(blkg, pos_cgrp, ctx.blkg) + tg_update_has_rules(blkg_to_tg(blkg)); + + /* + * We're already holding queue_lock and know @tg is valid. Let's + * apply the new config directly. + * + * Restart the slices for both READ and WRITES. It might happen + * that a group's limit are dropped suddenly and we don't want to + * account recently dispatched IO with new low rate. + */ + throtl_start_new_slice(tg, 0); + throtl_start_new_slice(tg, 1); + + if (tg->flags & THROTL_TG_PENDING) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(sq->parent_sq, true); + } blkg_conf_finish(&ctx); return 0; @@ -1092,7 +1461,7 @@ static void throtl_shutdown_wq(struct request_queue *q) { struct throtl_data *td = q->td; - cancel_delayed_work_sync(&td->throtl_work); + cancel_work_sync(&td->dispatch_work); } static struct blkcg_policy blkcg_policy_throtl = { @@ -1100,6 +1469,7 @@ static struct blkcg_policy blkcg_policy_throtl = { .cftypes = throtl_files, .pd_init_fn = throtl_pd_init, + .pd_online_fn = throtl_pd_online, .pd_exit_fn = throtl_pd_exit, .pd_reset_stats_fn = throtl_pd_reset_stats, }; @@ -1107,15 +1477,16 @@ static struct blkcg_policy blkcg_policy_throtl = { bool blk_throtl_bio(struct request_queue *q, struct bio *bio) { struct throtl_data *td = q->td; + struct throtl_qnode *qn = NULL; struct throtl_grp *tg; - bool rw = bio_data_dir(bio), update_disptime = true; + struct throtl_service_queue *sq; + bool rw = bio_data_dir(bio); struct blkcg *blkcg; bool throttled = false; - if (bio->bi_rw & REQ_THROTTLED) { - bio->bi_rw &= ~REQ_THROTTLED; + /* see throtl_charge_bio() */ + if (bio->bi_rw & REQ_THROTTLED) goto out; - } /* * A throtl_grp pointer retrieved under rcu can be used to access @@ -1126,7 +1497,7 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio) blkcg = bio_blkcg(bio); tg = throtl_lookup_tg(td, blkcg); if (tg) { - if (tg_no_rule_group(tg, rw)) { + if (!tg->has_rules[rw]) { throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw); goto out_unlock_rcu; @@ -1142,18 +1513,18 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio) if (unlikely(!tg)) goto out_unlock; - if (tg->nr_queued[rw]) { - /* - * There is already another bio queued in same dir. No - * need to update dispatch time. - */ - update_disptime = false; - goto queue_bio; + sq = &tg->service_queue; - } + while (true) { + /* throtl is FIFO - if bios are already queued, should queue */ + if (sq->nr_queued[rw]) + break; + + /* if above limits, break to queue */ + if (!tg_may_dispatch(tg, bio, NULL)) + break; - /* Bio is with-in rate limit of group */ - if (tg_may_dispatch(td, tg, bio, NULL)) { + /* within limits, let's charge and dispatch directly */ throtl_charge_bio(tg, bio); /* @@ -1167,25 +1538,41 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio) * * So keep on trimming slice even if bio is not queued. */ - throtl_trim_slice(td, tg, rw); - goto out_unlock; + throtl_trim_slice(tg, rw); + + /* + * @bio passed through this layer without being throttled. + * Climb up the ladder. If we''re already at the top, it + * can be executed directly. + */ + qn = &tg->qnode_on_parent[rw]; + sq = sq->parent_sq; + tg = sq_to_tg(sq); + if (!tg) + goto out_unlock; } -queue_bio: - throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu" - " iodisp=%u iops=%u queued=%d/%d", - rw == READ ? 'R' : 'W', - tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], - tg->io_disp[rw], tg->iops[rw], - tg->nr_queued[READ], tg->nr_queued[WRITE]); + /* out-of-limit, queue to @tg */ + throtl_log(sq, "[%c] bio. bdisp=%llu sz=%u bps=%llu iodisp=%u iops=%u queued=%d/%d", + rw == READ ? 'R' : 'W', + tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], + tg->io_disp[rw], tg->iops[rw], + sq->nr_queued[READ], sq->nr_queued[WRITE]); bio_associate_current(bio); - throtl_add_bio_tg(q->td, tg, bio); + tg->td->nr_queued[rw]++; + throtl_add_bio_tg(bio, qn, tg); throttled = true; - if (update_disptime) { - tg_update_disptime(td, tg); - throtl_schedule_next_dispatch(td); + /* + * Update @tg's dispatch time and force schedule dispatch if @tg + * was empty before @bio. The forced scheduling isn't likely to + * cause undue delay as @bio is likely to be dispatched directly if + * its @tg's disptime is not in the future. + */ + if (tg->flags & THROTL_TG_WAS_EMPTY) { + tg_update_disptime(tg); + throtl_schedule_next_dispatch(tg->service_queue.parent_sq, true); } out_unlock: @@ -1193,9 +1580,38 @@ out_unlock: out_unlock_rcu: rcu_read_unlock(); out: + /* + * As multiple blk-throtls may stack in the same issue path, we + * don't want bios to leave with the flag set. Clear the flag if + * being issued. + */ + if (!throttled) + bio->bi_rw &= ~REQ_THROTTLED; return throttled; } +/* + * Dispatch all bios from all children tg's queued on @parent_sq. On + * return, @parent_sq is guaranteed to not have any active children tg's + * and all bios from previously active tg's are on @parent_sq->bio_lists[]. + */ +static void tg_drain_bios(struct throtl_service_queue *parent_sq) +{ + struct throtl_grp *tg; + + while ((tg = throtl_rb_first(parent_sq))) { + struct throtl_service_queue *sq = &tg->service_queue; + struct bio *bio; + + throtl_dequeue_tg(tg); + + while ((bio = throtl_peek_queued(&sq->queued[READ]))) + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + while ((bio = throtl_peek_queued(&sq->queued[WRITE]))) + tg_dispatch_one_bio(tg, bio_data_dir(bio)); + } +} + /** * blk_throtl_drain - drain throttled bios * @q: request_queue to drain throttled bios for @@ -1206,27 +1622,36 @@ void blk_throtl_drain(struct request_queue *q) __releases(q->queue_lock) __acquires(q->queue_lock) { struct throtl_data *td = q->td; - struct throtl_rb_root *st = &td->tg_service_tree; - struct throtl_grp *tg; - struct bio_list bl; + struct blkcg_gq *blkg; + struct cgroup *pos_cgrp; struct bio *bio; + int rw; queue_lockdep_assert_held(q); + rcu_read_lock(); + + /* + * Drain each tg while doing post-order walk on the blkg tree, so + * that all bios are propagated to td->service_queue. It'd be + * better to walk service_queue tree directly but blkg walk is + * easier. + */ + blkg_for_each_descendant_post(blkg, pos_cgrp, td->queue->root_blkg) + tg_drain_bios(&blkg_to_tg(blkg)->service_queue); - bio_list_init(&bl); + tg_drain_bios(&td_root_tg(td)->service_queue); - while ((tg = throtl_rb_first(st))) { - throtl_dequeue_tg(td, tg); + /* finally, transfer bios from top-level tg's into the td */ + tg_drain_bios(&td->service_queue); - while ((bio = bio_list_peek(&tg->bio_lists[READ]))) - tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); - while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) - tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); - } + rcu_read_unlock(); spin_unlock_irq(q->queue_lock); - while ((bio = bio_list_pop(&bl))) - generic_make_request(bio); + /* all bios now should be in td->service_queue, issue them */ + for (rw = READ; rw <= WRITE; rw++) + while ((bio = throtl_pop_queued(&td->service_queue.queued[rw], + NULL))) + generic_make_request(bio); spin_lock_irq(q->queue_lock); } @@ -1240,9 +1665,8 @@ int blk_throtl_init(struct request_queue *q) if (!td) return -ENOMEM; - td->tg_service_tree = THROTL_RB_ROOT; - td->limits_changed = false; - INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); + INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn); + throtl_service_queue_init(&td->service_queue, NULL); q->td = td; td->queue = q; |