block: move blk-throtl fast path inline

Even if no policies are defined, we spend ~2% of the total IO time
checking. Move the fast path inline.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 182 insertions, 0 deletions

diff --git a/block/blk-throttle.h b/block/blk-throttle.h
new file mode 100644
index 000000000000..175f03abd9e4
--- /dev/null
+++ b/block/blk-throttle.h
@@ -0,0 +1,182 @@
+#ifndef BLK_THROTTLE_H
+#define BLK_THROTTLE_H
+
+#include "blk-cgroup-rwstat.h"
+
+/*
+ * 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_cached	pending_tree;	/* RB tree of active tgs */
+	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 {
+	LIMIT_LOW,
+	LIMIT_MAX,
+	LIMIT_CNT,
+};
+
+struct throtl_grp {
+	/* must be the first member */
+	struct blkg_policy_data pd;
+
+	/* 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
+	 * key to sort active groups in service tree.
+	 */
+	unsigned long disptime;
+
+	unsigned int flags;
+
+	/* are there any throtl rules between this group and td? */
+	bool has_rules[2];
+
+	/* internally used bytes per second rate limits */
+	uint64_t bps[2][LIMIT_CNT];
+	/* user configured bps limits */
+	uint64_t bps_conf[2][LIMIT_CNT];
+
+	/* internally used IOPS limits */
+	unsigned int iops[2][LIMIT_CNT];
+	/* user configured IOPS limits */
+	unsigned int iops_conf[2][LIMIT_CNT];
+
+	/* Number of bytes dispatched in current slice */
+	uint64_t bytes_disp[2];
+	/* Number of bio's dispatched in current slice */
+	unsigned int io_disp[2];
+
+	unsigned long last_low_overflow_time[2];
+
+	uint64_t last_bytes_disp[2];
+	unsigned int last_io_disp[2];
+
+	unsigned long last_check_time;
+
+	unsigned long latency_target; /* us */
+	unsigned long latency_target_conf; /* us */
+	/* When did we start a new slice */
+	unsigned long slice_start[2];
+	unsigned long slice_end[2];
+
+	unsigned long last_finish_time; /* ns / 1024 */
+	unsigned long checked_last_finish_time; /* ns / 1024 */
+	unsigned long avg_idletime; /* ns / 1024 */
+	unsigned long idletime_threshold; /* us */
+	unsigned long idletime_threshold_conf; /* us */
+
+	unsigned int bio_cnt; /* total bios */
+	unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
+	unsigned long bio_cnt_reset_time;
+
+	atomic_t io_split_cnt[2];
+	atomic_t last_io_split_cnt[2];
+
+	struct blkg_rwstat stat_bytes;
+	struct blkg_rwstat stat_ios;
+};
+
+extern struct blkcg_policy blkcg_policy_throtl;
+
+static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
+{
+	return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
+}
+
+static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
+{
+	return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
+}
+
+/*
+ * Internal throttling interface
+ */
+#ifndef CONFIG_BLK_DEV_THROTTLING
+static inline int blk_throtl_init(struct request_queue *q) { return 0; }
+static inline void blk_throtl_exit(struct request_queue *q) { }
+static inline void blk_throtl_register_queue(struct request_queue *q) { }
+static inline void blk_throtl_charge_bio_split(struct bio *bio) { }
+static inline bool blk_throtl_bio(struct bio *bio) { return false; }
+#else /* CONFIG_BLK_DEV_THROTTLING */
+int blk_throtl_init(struct request_queue *q);
+void blk_throtl_exit(struct request_queue *q);
+void blk_throtl_register_queue(struct request_queue *q);
+void blk_throtl_charge_bio_split(struct bio *bio);
+bool __blk_throtl_bio(struct bio *bio);
+static inline bool blk_throtl_bio(struct bio *bio)
+{
+	struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
+
+	if (bio_flagged(bio, BIO_THROTTLED))
+		return false;
+	if (!tg->has_rules[bio_data_dir(bio)])
+		return false;
+
+	return __blk_throtl_bio(bio);
+}
+#endif /* CONFIG_BLK_DEV_THROTTLING */
+
+#endif