4 #include "blk-cgroup-rwstat.h"
7 * To implement hierarchical throttling, throtl_grps form a tree and bios
8 * are dispatched upwards level by level until they reach the top and get
9 * issued. When dispatching bios from the children and local group at each
10 * level, if the bios are dispatched into a single bio_list, there's a risk
11 * of a local or child group which can queue many bios at once filling up
12 * the list starving others.
14 * To avoid such starvation, dispatched bios are queued separately
15 * according to where they came from. When they are again dispatched to
16 * the parent, they're popped in round-robin order so that no single source
17 * hogs the dispatch window.
19 * throtl_qnode is used to keep the queued bios separated by their sources.
20 * Bios are queued to throtl_qnode which in turn is queued to
21 * throtl_service_queue and then dispatched in round-robin order.
23 * It's also used to track the reference counts on blkg's. A qnode always
24 * belongs to a throtl_grp and gets queued on itself or the parent, so
25 * incrementing the reference of the associated throtl_grp when a qnode is
26 * queued and decrementing when dequeued is enough to keep the whole blkg
27 * tree pinned while bios are in flight.
30 struct list_head node; /* service_queue->queued[] */
31 struct bio_list bios; /* queued bios */
32 struct throtl_grp *tg; /* tg this qnode belongs to */
35 struct throtl_service_queue {
36 struct throtl_service_queue *parent_sq; /* the parent service_queue */
39 * Bios queued directly to this service_queue or dispatched from
40 * children throtl_grp's.
42 struct list_head queued[2]; /* throtl_qnode [READ/WRITE] */
43 unsigned int nr_queued[2]; /* number of queued bios */
46 * RB tree of active children throtl_grp's, which are sorted by
49 struct rb_root_cached pending_tree; /* RB tree of active tgs */
50 unsigned int nr_pending; /* # queued in the tree */
51 unsigned long first_pending_disptime; /* disptime of the first tg */
52 struct timer_list pending_timer; /* fires on first_pending_disptime */
56 THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
57 THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
58 THROTL_TG_CANCELING = 1 << 2, /* starts to cancel bio */
62 /* must be the first member */
63 struct blkg_policy_data pd;
65 /* active throtl group service_queue member */
66 struct rb_node rb_node;
68 /* throtl_data this group belongs to */
69 struct throtl_data *td;
71 /* this group's service queue */
72 struct throtl_service_queue service_queue;
75 * qnode_on_self is used when bios are directly queued to this
76 * throtl_grp so that local bios compete fairly with bios
77 * dispatched from children. qnode_on_parent is used when bios are
78 * dispatched from this throtl_grp into its parent and will compete
79 * with the sibling qnode_on_parents and the parent's
82 struct throtl_qnode qnode_on_self[2];
83 struct throtl_qnode qnode_on_parent[2];
86 * Dispatch time in jiffies. This is the estimated time when group
87 * will unthrottle and is ready to dispatch more bio. It is used as
88 * key to sort active groups in service tree.
90 unsigned long disptime;
94 /* are there any throtl rules between this group and td? */
95 bool has_rules_bps[2];
96 bool has_rules_iops[2];
98 /* internally used bytes per second rate limits */
100 /* user configured bps limits */
101 uint64_t bps_conf[2];
103 /* internally used IOPS limits */
104 unsigned int iops[2];
105 /* user configured IOPS limits */
106 unsigned int iops_conf[2];
108 /* Number of bytes dispatched in current slice */
109 uint64_t bytes_disp[2];
110 /* Number of bio's dispatched in current slice */
111 unsigned int io_disp[2];
113 unsigned long last_low_overflow_time[2];
115 uint64_t last_bytes_disp[2];
116 unsigned int last_io_disp[2];
119 * The following two fields are updated when new configuration is
120 * submitted while some bios are still throttled, they record how many
121 * bytes/ios are waited already in previous configuration, and they will
122 * be used to calculate wait time under new configuration.
124 long long carryover_bytes[2];
125 int carryover_ios[2];
127 unsigned long last_check_time;
129 /* When did we start a new slice */
130 unsigned long slice_start[2];
131 unsigned long slice_end[2];
133 struct blkg_rwstat stat_bytes;
134 struct blkg_rwstat stat_ios;
137 extern struct blkcg_policy blkcg_policy_throtl;
139 static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
141 return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
144 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
146 return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
150 * Internal throttling interface
152 #ifndef CONFIG_BLK_DEV_THROTTLING
153 static inline int blk_throtl_init(struct gendisk *disk) { return 0; }
154 static inline void blk_throtl_exit(struct gendisk *disk) { }
155 static inline void blk_throtl_register(struct gendisk *disk) { }
156 static inline bool blk_throtl_bio(struct bio *bio) { return false; }
157 static inline void blk_throtl_cancel_bios(struct gendisk *disk) { }
158 #else /* CONFIG_BLK_DEV_THROTTLING */
159 int blk_throtl_init(struct gendisk *disk);
160 void blk_throtl_exit(struct gendisk *disk);
161 void blk_throtl_register(struct gendisk *disk);
162 bool __blk_throtl_bio(struct bio *bio);
163 void blk_throtl_cancel_bios(struct gendisk *disk);
165 static inline bool blk_should_throtl(struct bio *bio)
167 struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
168 int rw = bio_data_dir(bio);
170 if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
171 if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
172 bio_set_flag(bio, BIO_CGROUP_ACCT);
173 blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
174 bio->bi_iter.bi_size);
176 blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
179 /* iops limit is always counted */
180 if (tg->has_rules_iops[rw])
183 if (tg->has_rules_bps[rw] && !bio_flagged(bio, BIO_BPS_THROTTLED))
189 static inline bool blk_throtl_bio(struct bio *bio)
192 if (!blk_should_throtl(bio))
195 return __blk_throtl_bio(bio);
197 #endif /* CONFIG_BLK_DEV_THROTTLING */