linux/block/blk-throttle.h
Yu Kuai a3166c5170 blk-throttle: delay initialization until configuration
Other cgroup policy like bfq, iocost are lazy-initialized when they are
configured for the first time for the device, but blk-throttle is
initialized unconditionally from blkcg_init_disk().

Delay initialization of blk-throttle as well, to save some cpu and
memory overhead if it's not configured.

Noted that once it's initialized, it can't be destroyed until disk
removal, even if it's disabled.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240509121107.3195568-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-05-09 09:44:56 -06:00

210 lines
6.2 KiB
C

#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 tg_state_flags {
THROTL_TG_PENDING = 1 << 0, /* on parent's pending tree */
THROTL_TG_WAS_EMPTY = 1 << 1, /* bio_lists[] became non-empty */
THROTL_TG_CANCELING = 1 << 2, /* starts to cancel bio */
};
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_bps[2];
bool has_rules_iops[2];
/* internally used bytes per second rate limits */
uint64_t bps[2];
/* user configured bps limits */
uint64_t bps_conf[2];
/* internally used IOPS limits */
unsigned int iops[2];
/* user configured IOPS limits */
unsigned int iops_conf[2];
/* 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];
/*
* The following two fields are updated when new configuration is
* submitted while some bios are still throttled, they record how many
* bytes/ios are waited already in previous configuration, and they will
* be used to calculate wait time under new configuration.
*/
long long carryover_bytes[2];
int carryover_ios[2];
unsigned long last_check_time;
/* When did we start a new slice */
unsigned long slice_start[2];
unsigned long slice_end[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 void blk_throtl_exit(struct gendisk *disk) { }
static inline bool blk_throtl_bio(struct bio *bio) { return false; }
static inline void blk_throtl_cancel_bios(struct gendisk *disk) { }
#else /* CONFIG_BLK_DEV_THROTTLING */
void blk_throtl_exit(struct gendisk *disk);
bool __blk_throtl_bio(struct bio *bio);
void blk_throtl_cancel_bios(struct gendisk *disk);
static inline bool blk_throtl_activated(struct request_queue *q)
{
return q->td != NULL;
}
static inline bool blk_should_throtl(struct bio *bio)
{
struct throtl_grp *tg;
int rw = bio_data_dir(bio);
/*
* This is called under bio_queue_enter(), and it's synchronized with
* the activation of blk-throtl, which is protected by
* blk_mq_freeze_queue().
*/
if (!blk_throtl_activated(bio->bi_bdev->bd_queue))
return false;
tg = blkg_to_tg(bio->bi_blkg);
if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) {
if (!bio_flagged(bio, BIO_CGROUP_ACCT)) {
bio_set_flag(bio, BIO_CGROUP_ACCT);
blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf,
bio->bi_iter.bi_size);
}
blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1);
}
/* iops limit is always counted */
if (tg->has_rules_iops[rw])
return true;
if (tg->has_rules_bps[rw] && !bio_flagged(bio, BIO_BPS_THROTTLED))
return true;
return false;
}
static inline bool blk_throtl_bio(struct bio *bio)
{
if (!blk_should_throtl(bio))
return false;
return __blk_throtl_bio(bio);
}
#endif /* CONFIG_BLK_DEV_THROTTLING */
#endif