/* A workqueue to queue throttle related work */
static struct workqueue_struct *kthrotld_workqueue;
+/*
+ * 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 */
+};
+
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)
/* 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
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];
unsigned int nr_undestroyed_grps;
/* Work for dispatching throttled bios */
- struct delayed_work dispatch_work;
+ struct work_struct dispatch_work;
};
/* list and work item to allocate percpu group stats */
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;
return blkg_to_tg(td->queue->root_blkg);
}
-#define throtl_log_tg(tg, fmt, args...) do { \
- char __pbuf[128]; \
+/**
+ * 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;
+}
+
+/**
+ * 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);
+
+ 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)); \
\
- blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf)); \
- blk_add_trace_msg((tg)->td->queue, "throtl %s " fmt, __pbuf, ##args); \
+ (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); \
+ } 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)
-
/*
* 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
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)
+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);
+ }
- throtl_service_queue_init(&tg->service_queue);
RB_CLEAR_NODE(&tg->rb_node);
- tg->td = blkg->q->td;
- bio_list_init(&tg->bio_lists[0]);
- bio_list_init(&tg->bio_lists[1]);
+ tg->td = td;
tg->bps[READ] = -1;
tg->bps[WRITE] = -1;
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);
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)
parent_sq->first_pending_disptime = tg->disptime;
}
-static void tg_service_queue_add(struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+static void tg_service_queue_add(struct throtl_grp *tg)
{
+ 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;
rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
}
-static void __throtl_enqueue_tg(struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+static void __throtl_enqueue_tg(struct throtl_grp *tg)
{
- tg_service_queue_add(tg, parent_sq);
+ tg_service_queue_add(tg);
tg->flags |= THROTL_TG_PENDING;
- parent_sq->nr_pending++;
+ tg->service_queue.parent_sq->nr_pending++;
}
-static void throtl_enqueue_tg(struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+static void throtl_enqueue_tg(struct throtl_grp *tg)
{
if (!(tg->flags & THROTL_TG_PENDING))
- __throtl_enqueue_tg(tg, parent_sq);
+ __throtl_enqueue_tg(tg);
}
-static void __throtl_dequeue_tg(struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+static void __throtl_dequeue_tg(struct throtl_grp *tg)
{
- throtl_rb_erase(&tg->rb_node, parent_sq);
+ throtl_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
tg->flags &= ~THROTL_TG_PENDING;
}
-static void throtl_dequeue_tg(struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+static void throtl_dequeue_tg(struct throtl_grp *tg)
{
if (tg->flags & THROTL_TG_PENDING)
- __throtl_dequeue_tg(tg, parent_sq);
+ __throtl_dequeue_tg(tg);
}
/* Call with queue lock held */
-static void throtl_schedule_delayed_work(struct throtl_data *td,
- unsigned long delay)
+static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
+ unsigned long expires)
{
- struct delayed_work *dwork = &td->dispatch_work;
-
- mod_delayed_work(kthrotld_workqueue, dwork, delay);
- throtl_log(td, "schedule work. delay=%lu jiffies=%lu", delay, jiffies);
+ 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_service_queue *sq = &td->service_queue;
-
/* any pending children left? */
if (!sq->nr_pending)
- return;
+ return true;
update_min_dispatch_time(sq);
- if (time_before_eq(sq->first_pending_disptime, jiffies))
- throtl_schedule_delayed_work(td, 0);
- else
- throtl_schedule_delayed_work(td, sq->first_pending_disptime - jiffies);
+ /* 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;
+ }
+
+ /* tell the caller to continue dispatching */
+ return false;
+}
+
+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_grp *tg, bool rw)
tg->io_disp[rw] = 0;
tg->slice_start[rw] = jiffies;
tg->slice_end[rw] = jiffies + throtl_slice;
- throtl_log_tg(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_grp *tg, bool rw,
unsigned long jiffy_end)
{
tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
- throtl_log_tg(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 */
tg->slice_start[rw] += nr_slices * throtl_slice;
- throtl_log_tg(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_grp *tg, struct bio *bio,
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
* 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) {
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 bio *bio, struct throtl_grp *tg,
- struct throtl_service_queue *parent_sq)
+/**
+ * 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]++;
- tg->td->nr_queued[rw]++;
- throtl_enqueue_tg(tg, parent_sq);
+ 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_grp *tg,
- struct throtl_service_queue *parent_sq)
+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])))
+ if ((bio = throtl_peek_queued(&sq->queued[READ])))
tg_may_dispatch(tg, bio, &read_wait);
- if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
+ 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(tg, parent_sq);
+ throtl_dequeue_tg(tg);
tg->disptime = disptime;
- throtl_enqueue_tg(tg, parent_sq);
+ throtl_enqueue_tg(tg);
+
+ /* see throtl_add_bio_tg() */
+ tg->flags &= ~THROTL_TG_WAS_EMPTY;
}
-static void tg_dispatch_one_bio(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));
+}
- BUG_ON(tg->td->nr_queued[rw] <= 0);
- tg->td->nr_queued[rw]--;
+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;
+
+ /*
+ * @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;
+
+ /*
+ * 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_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;
/* Try to dispatch 75% READS and 25% WRITES */
- while ((bio = bio_list_peek(&tg->bio_lists[READ])) &&
+ while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
tg_may_dispatch(tg, bio, NULL)) {
- tg_dispatch_one_bio(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])) &&
+ while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
tg_may_dispatch(tg, bio, NULL)) {
- tg_dispatch_one_bio(tg, bio_data_dir(bio), bl);
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
nr_writes++;
if (nr_writes >= max_nr_writes)
return nr_reads + nr_writes;
}
-static int throtl_select_dispatch(struct throtl_service_queue *parent_sq,
- struct bio_list *bl)
+static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
{
unsigned int nr_disp = 0;
- struct throtl_grp *tg;
while (1) {
- tg = throtl_rb_first(parent_sq);
+ struct throtl_grp *tg = throtl_rb_first(parent_sq);
+ struct throtl_service_queue *sq = &tg->service_queue;
if (!tg)
break;
if (time_before(jiffies, tg->disptime))
break;
- throtl_dequeue_tg(tg, parent_sq);
+ throtl_dequeue_tg(tg);
- nr_disp += throtl_dispatch_tg(tg, bl);
+ nr_disp += throtl_dispatch_tg(tg);
- if (tg->nr_queued[0] || tg->nr_queued[1])
- tg_update_disptime(tg, parent_sq);
+ if (sq->nr_queued[0] || sq->nr_queued[1])
+ tg_update_disptime(tg);
if (nr_disp >= throtl_quantum)
break;
return nr_disp;
}
-/* work function to dispatch throttled bios */
-void blk_throtl_dispatch_work_fn(struct work_struct *work)
+/**
+ * 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_data *td = container_of(to_delayed_work(work),
- struct throtl_data, dispatch_work);
+ 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;
- unsigned int nr_disp = 0;
- struct bio_list bio_list_on_stack;
- struct bio *bio;
- struct blk_plug plug;
+ struct throtl_service_queue *parent_sq;
+ bool dispatched;
+ int ret;
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;
+ }
- bio_list_init(&bio_list_on_stack);
+ if (throtl_schedule_next_dispatch(sq, false))
+ break;
- throtl_log(td, "dispatch nr_queued=%u read=%u write=%u",
- td->nr_queued[READ] + td->nr_queued[WRITE],
- td->nr_queued[READ], td->nr_queued[WRITE]);
+ /* this dispatch windows is still open, relax and repeat */
+ spin_unlock_irq(q->queue_lock);
+ cpu_relax();
+ spin_lock_irq(q->queue_lock);
+ }
- nr_disp = throtl_select_dispatch(&td->service_queue, &bio_list_on_stack);
+ if (!dispatched)
+ goto out_unlock;
- if (nr_disp)
- throtl_log(td, "bios disp=%u", nr_disp);
+ 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);
+}
- throtl_schedule_next_dispatch(td);
+/**
+ * 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 = 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;
+ int rw;
+ bio_list_init(&bio_list_on_stack);
+
+ 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);
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);
return ret;
tg = blkg_to_tg(ctx.blkg);
- td = ctx.blkg->q->td;
+ sq = &tg->service_queue;
if (!ctx.v)
ctx.v = -1;
else
*(unsigned int *)((void *)tg + cft->private) = ctx.v;
- throtl_log_tg(tg, "limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
- tg->bps[READ], tg->bps[WRITE],
- tg->iops[READ], tg->iops[WRITE]);
+ 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
throtl_start_new_slice(tg, 1);
if (tg->flags & THROTL_TG_PENDING) {
- tg_update_disptime(tg, &td->service_queue);
- throtl_schedule_next_dispatch(td);
+ tg_update_disptime(tg);
+ throtl_schedule_next_dispatch(sq->parent_sq, true);
}
blkg_conf_finish(&ctx);
{
struct throtl_data *td = q->td;
- cancel_delayed_work_sync(&td->dispatch_work);
+ cancel_work_sync(&td->dispatch_work);
}
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,
};
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
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;
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(tg, bio, NULL)) {
+ /* within limits, let's charge and dispatch directly */
throtl_charge_bio(tg, bio);
/*
* So keep on trimming slice even if bio is not queued.
*/
throtl_trim_slice(tg, rw);
- goto out_unlock;
+
+ /*
+ * @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(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(bio, tg, &q->td->service_queue);
+ tg->td->nr_queued[rw]++;
+ throtl_add_bio_tg(bio, qn, tg);
throttled = true;
- if (update_disptime) {
- tg_update_disptime(tg, &td->service_queue);
- 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:
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
__releases(q->queue_lock) __acquires(q->queue_lock)
{
struct throtl_data *td = q->td;
- struct throtl_service_queue *parent_sq = &td->service_queue;
- 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();
- bio_list_init(&bl);
+ /*
+ * 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);
- while ((tg = throtl_rb_first(parent_sq))) {
- throtl_dequeue_tg(tg, parent_sq);
+ tg_drain_bios(&td_root_tg(td)->service_queue);
- while ((bio = bio_list_peek(&tg->bio_lists[READ])))
- tg_dispatch_one_bio(tg, bio_data_dir(bio), &bl);
- while ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
- tg_dispatch_one_bio(tg, bio_data_dir(bio), &bl);
- }
+ /* finally, transfer bios from top-level tg's into the td */
+ tg_drain_bios(&td->service_queue);
+
+ 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);
}
if (!td)
return -ENOMEM;
- INIT_DELAYED_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
- throtl_service_queue_init(&td->service_queue);
+ INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
+ throtl_service_queue_init(&td->service_queue, NULL);
q->td = td;
td->queue = q;
projects / cascardo / linux.git / blobdiff