block/blk-throttle.h

   1 #ifndef BLK_THROTTLE_H
   2 #define BLK_THROTTLE_H
   3
   4 #include "blk-cgroup-rwstat.h"
   5
   6 /*
   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.
  13  *
  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.
  18  *
  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.
  22  *
  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.
  28  */
  29 struct throtl_qnode {
  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 */
  33 };
  34
  35 struct throtl_service_queue {
  36         struct throtl_service_queue *parent_sq; /* the parent service_queue */
  37
  38         /*
  39          * Bios queued directly to this service_queue or dispatched from
  40          * children throtl_grp's.
  41          */
  42         struct list_head        queued[2];      /* throtl_qnode [READ/WRITE] */
  43         unsigned int            nr_queued[2];   /* number of queued bios */
  44
  45         /*
  46          * RB tree of active children throtl_grp's, which are sorted by
  47          * their ->disptime.
  48          */
  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 */
  53 };
  54
  55 enum tg_state_flags {
  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_HAS_IOPS_LIMIT = 1 << 2,      /* tg has iops limit */
  59         THROTL_TG_CANCELING     = 1 << 3,       /* starts to cancel bio */
  60 };
  61
  62 enum {
  63         LIMIT_LOW,
  64         LIMIT_MAX,
  65         LIMIT_CNT,
  66 };
  67
  68 struct throtl_grp {
  69         /* must be the first member */
  70         struct blkg_policy_data pd;
  71
  72         /* active throtl group service_queue member */
  73         struct rb_node rb_node;
  74
  75         /* throtl_data this group belongs to */
  76         struct throtl_data *td;
  77
  78         /* this group's service queue */
  79         struct throtl_service_queue service_queue;
  80
  81         /*
  82          * qnode_on_self is used when bios are directly queued to this
  83          * throtl_grp so that local bios compete fairly with bios
  84          * dispatched from children.  qnode_on_parent is used when bios are
  85          * dispatched from this throtl_grp into its parent and will compete
  86          * with the sibling qnode_on_parents and the parent's
  87          * qnode_on_self.
  88          */
  89         struct throtl_qnode qnode_on_self[2];
  90         struct throtl_qnode qnode_on_parent[2];
  91
  92         /*
  93          * Dispatch time in jiffies. This is the estimated time when group
  94          * will unthrottle and is ready to dispatch more bio. It is used as
  95          * key to sort active groups in service tree.
  96          */
  97         unsigned long disptime;
  98
  99         unsigned int flags;
 100
 101         /* are there any throtl rules between this group and td? */
 102         bool has_rules[2];
 103
 104         /* internally used bytes per second rate limits */
 105         uint64_t bps[2][LIMIT_CNT];
 106         /* user configured bps limits */
 107         uint64_t bps_conf[2][LIMIT_CNT];
 108
 109         /* internally used IOPS limits */
 110         unsigned int iops[2][LIMIT_CNT];
 111         /* user configured IOPS limits */
 112         unsigned int iops_conf[2][LIMIT_CNT];
 113
 114         /* Number of bytes dispatched in current slice */
 115         uint64_t bytes_disp[2];
 116         /* Number of bio's dispatched in current slice */
 117         unsigned int io_disp[2];
 118
 119         unsigned long last_low_overflow_time[2];
 120
 121         uint64_t last_bytes_disp[2];
 122         unsigned int last_io_disp[2];
 123
 124         unsigned long last_check_time;
 125
 126         unsigned long latency_target; /* us */
 127         unsigned long latency_target_conf; /* us */
 128         /* When did we start a new slice */
 129         unsigned long slice_start[2];
 130         unsigned long slice_end[2];
 131
 132         unsigned long last_finish_time; /* ns / 1024 */
 133         unsigned long checked_last_finish_time; /* ns / 1024 */
 134         unsigned long avg_idletime; /* ns / 1024 */
 135         unsigned long idletime_threshold; /* us */
 136         unsigned long idletime_threshold_conf; /* us */
 137
 138         unsigned int bio_cnt; /* total bios */
 139         unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
 140         unsigned long bio_cnt_reset_time;
 141
 142         struct blkg_rwstat stat_bytes;
 143         struct blkg_rwstat stat_ios;
 144 };
 145
 146 extern struct blkcg_policy blkcg_policy_throtl;
 147
 148 static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
 149 {
 150         return pd ? container_of(pd, struct throtl_grp, pd) : NULL;
 151 }
 152
 153 static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg)
 154 {
 155         return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl));
 156 }
 157
 158 /*
 159  * Internal throttling interface
 160  */
 161 #ifndef CONFIG_BLK_DEV_THROTTLING
 162 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 163 static inline void blk_throtl_exit(struct request_queue *q) { }
 164 static inline void blk_throtl_register_queue(struct request_queue *q) { }
 165 static inline bool blk_throtl_bio(struct bio *bio) { return false; }
 166 static inline void blk_throtl_cancel_bios(struct request_queue *q) { }
 167 #else /* CONFIG_BLK_DEV_THROTTLING */
 168 int blk_throtl_init(struct request_queue *q);
 169 void blk_throtl_exit(struct request_queue *q);
 170 void blk_throtl_register_queue(struct request_queue *q);
 171 bool __blk_throtl_bio(struct bio *bio);
 172 void blk_throtl_cancel_bios(struct request_queue *q);
 173 static inline bool blk_throtl_bio(struct bio *bio)
 174 {
 175         struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg);
 176
 177         /* no need to throttle bps any more if the bio has been throttled */
 178         if (bio_flagged(bio, BIO_THROTTLED) &&
 179             !(tg->flags & THROTL_TG_HAS_IOPS_LIMIT))
 180                 return false;
 181
 182         if (!tg->has_rules[bio_data_dir(bio)])
 183                 return false;
 184
 185         return __blk_throtl_bio(bio);
 186 }
 187 #endif /* CONFIG_BLK_DEV_THROTTLING */
 188
 189 #endif