kernel_optimize_test/block/blk-throttle.c
Shaohua Li 111be88398 block-throttle: avoid double charge
If a bio is throttled and split after throttling, the bio could be
resubmited and enters the throttling again. This will cause part of the
bio to be charged multiple times. If the cgroup has an IO limit, the
double charge will significantly harm the performance. The bio split
becomes quite common after arbitrary bio size change.

To fix this, we always set the BIO_THROTTLED flag if a bio is throttled.
If the bio is cloned/split, we copy the flag to new bio too to avoid a
double charge. However, cloned bio could be directed to a new disk,
keeping the flag be a problem. The observation is we always set new disk
for the bio in this case, so we can clear the flag in bio_set_dev().

This issue exists for a long time, arbitrary bio size change just makes
it worse, so this should go into stable at least since v4.2.

V1-> V2: Not add extra field in bio based on discussion with Tejun

Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-12-20 11:10:17 -07:00

2493 lines
68 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Interface for controlling IO bandwidth on a request queue
*
* Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com>
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/blktrace_api.h>
#include <linux/blk-cgroup.h>
#include "blk.h"
/* Max dispatch from a group in 1 round */
static int throtl_grp_quantum = 8;
/* Total max dispatch from all groups in one round */
static int throtl_quantum = 32;
/* Throttling is performed over a slice and after that slice is renewed */
#define DFL_THROTL_SLICE_HD (HZ / 10)
#define DFL_THROTL_SLICE_SSD (HZ / 50)
#define MAX_THROTL_SLICE (HZ)
#define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
#define MIN_THROTL_BPS (320 * 1024)
#define MIN_THROTL_IOPS (10)
#define DFL_LATENCY_TARGET (-1L)
#define DFL_IDLE_THRESHOLD (0)
#define DFL_HD_BASELINE_LATENCY (4000L) /* 4ms */
#define LATENCY_FILTERED_SSD (0)
/*
* For HD, very small latency comes from sequential IO. Such IO is helpless to
* help determine if its IO is impacted by others, hence we ignore the IO
*/
#define LATENCY_FILTERED_HD (1000L) /* 1ms */
#define SKIP_LATENCY (((u64)1) << BLK_STAT_RES_SHIFT)
static struct blkcg_policy blkcg_policy_throtl;
/* 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)
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 disptached 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;
};
/* We measure latency for request size from <= 4k to >= 1M */
#define LATENCY_BUCKET_SIZE 9
struct latency_bucket {
unsigned long total_latency; /* ns / 1024 */
int samples;
};
struct avg_latency_bucket {
unsigned long latency; /* ns / 1024 */
bool valid;
};
struct throtl_data
{
/* service tree for active throtl groups */
struct throtl_service_queue service_queue;
struct request_queue *queue;
/* Total Number of queued bios on READ and WRITE lists */
unsigned int nr_queued[2];
unsigned int throtl_slice;
/* Work for dispatching throttled bios */
struct work_struct dispatch_work;
unsigned int limit_index;
bool limit_valid[LIMIT_CNT];
unsigned long low_upgrade_time;
unsigned long low_downgrade_time;
unsigned int scale;
struct latency_bucket tmp_buckets[LATENCY_BUCKET_SIZE];
struct avg_latency_bucket avg_buckets[LATENCY_BUCKET_SIZE];
struct latency_bucket __percpu *latency_buckets;
unsigned long last_calculate_time;
unsigned long filtered_latency;
bool track_bio_latency;
};
static void throtl_pending_timer_fn(struct timer_list *t);
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));
}
static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg)
{
return pd_to_blkg(&tg->pd);
}
/**
* 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 embedded 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);
}
/*
* cgroup's limit in LIMIT_MAX is scaled if low limit is set. This scale is to
* make the IO dispatch more smooth.
* Scale up: linearly scale up according to lapsed time since upgrade. For
* every throtl_slice, the limit scales up 1/2 .low limit till the
* limit hits .max limit
* Scale down: exponentially scale down if a cgroup doesn't hit its .low limit
*/
static uint64_t throtl_adjusted_limit(uint64_t low, struct throtl_data *td)
{
/* arbitrary value to avoid too big scale */
if (td->scale < 4096 && time_after_eq(jiffies,
td->low_upgrade_time + td->scale * td->throtl_slice))
td->scale = (jiffies - td->low_upgrade_time) / td->throtl_slice;
return low + (low >> 1) * td->scale;
}
static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
struct throtl_data *td;
uint64_t ret;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return U64_MAX;
td = tg->td;
ret = tg->bps[rw][td->limit_index];
if (ret == 0 && td->limit_index == LIMIT_LOW) {
/* intermediate node or iops isn't 0 */
if (!list_empty(&blkg->blkcg->css.children) ||
tg->iops[rw][td->limit_index])
return U64_MAX;
else
return MIN_THROTL_BPS;
}
if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
uint64_t adjusted;
adjusted = throtl_adjusted_limit(tg->bps[rw][LIMIT_LOW], td);
ret = min(tg->bps[rw][LIMIT_MAX], adjusted);
}
return ret;
}
static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
struct throtl_data *td;
unsigned int ret;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return UINT_MAX;
td = tg->td;
ret = tg->iops[rw][td->limit_index];
if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
/* intermediate node or bps isn't 0 */
if (!list_empty(&blkg->blkcg->css.children) ||
tg->bps[rw][td->limit_index])
return UINT_MAX;
else
return MIN_THROTL_IOPS;
}
if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
uint64_t adjusted;
adjusted = throtl_adjusted_limit(tg->iops[rw][LIMIT_LOW], td);
if (adjusted > UINT_MAX)
adjusted = UINT_MAX;
ret = min_t(unsigned int, tg->iops[rw][LIMIT_MAX], adjusted);
}
return ret;
}
#define request_bucket_index(sectors) \
clamp_t(int, order_base_2(sectors) - 3, 0, LATENCY_BUCKET_SIZE - 1)
/**
* 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".
*/
#define throtl_log(sq, fmt, args...) do { \
struct throtl_grp *__tg = sq_to_tg((sq)); \
struct throtl_data *__td = sq_to_td((sq)); \
\
(void)__td; \
if (likely(!blk_trace_note_message_enabled(__td->queue))) \
break; \
if ((__tg)) { \
blk_add_cgroup_trace_msg(__td->queue, \
tg_to_blkg(__tg)->blkcg, "throtl " fmt, ##args);\
} else { \
blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
} \
} while (0)
static inline unsigned int throtl_bio_data_size(struct bio *bio)
{
/* assume it's one sector */
if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
return 512;
return bio->bi_iter.bi_size;
}
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)
{
INIT_LIST_HEAD(&sq->queued[0]);
INIT_LIST_HEAD(&sq->queued[1]);
sq->pending_tree = RB_ROOT;
timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
}
static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
{
struct throtl_grp *tg;
int rw;
tg = kzalloc_node(sizeof(*tg), gfp, node);
if (!tg)
return NULL;
throtl_service_queue_init(&tg->service_queue);
for (rw = READ; rw <= WRITE; rw++) {
throtl_qnode_init(&tg->qnode_on_self[rw], tg);
throtl_qnode_init(&tg->qnode_on_parent[rw], tg);
}
RB_CLEAR_NODE(&tg->rb_node);
tg->bps[READ][LIMIT_MAX] = U64_MAX;
tg->bps[WRITE][LIMIT_MAX] = U64_MAX;
tg->iops[READ][LIMIT_MAX] = UINT_MAX;
tg->iops[WRITE][LIMIT_MAX] = UINT_MAX;
tg->bps_conf[READ][LIMIT_MAX] = U64_MAX;
tg->bps_conf[WRITE][LIMIT_MAX] = U64_MAX;
tg->iops_conf[READ][LIMIT_MAX] = UINT_MAX;
tg->iops_conf[WRITE][LIMIT_MAX] = UINT_MAX;
/* LIMIT_LOW will have default value 0 */
tg->latency_target = DFL_LATENCY_TARGET;
tg->latency_target_conf = DFL_LATENCY_TARGET;
tg->idletime_threshold = DFL_IDLE_THRESHOLD;
tg->idletime_threshold_conf = DFL_IDLE_THRESHOLD;
return &tg->pd;
}
static void throtl_pd_init(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
struct blkcg_gq *blkg = tg_to_blkg(tg);
struct throtl_data *td = blkg->q->td;
struct throtl_service_queue *sq = &tg->service_queue;
/*
* If on the default hierarchy, 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 not on the default hierarchy, 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.
*/
sq->parent_sq = &td->service_queue;
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
tg->td = td;
}
/*
* 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);
struct throtl_data *td = tg->td;
int rw;
for (rw = READ; rw <= WRITE; rw++)
tg->has_rules[rw] = (parent_tg && parent_tg->has_rules[rw]) ||
(td->limit_valid[td->limit_index] &&
(tg_bps_limit(tg, rw) != U64_MAX ||
tg_iops_limit(tg, rw) != UINT_MAX));
}
static void throtl_pd_online(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
/*
* 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(tg);
}
static void blk_throtl_update_limit_valid(struct throtl_data *td)
{
struct cgroup_subsys_state *pos_css;
struct blkcg_gq *blkg;
bool low_valid = false;
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
if (tg->bps[READ][LIMIT_LOW] || tg->bps[WRITE][LIMIT_LOW] ||
tg->iops[READ][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
low_valid = true;
}
rcu_read_unlock();
td->limit_valid[LIMIT_LOW] = low_valid;
}
static void throtl_upgrade_state(struct throtl_data *td);
static void throtl_pd_offline(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
tg->bps[READ][LIMIT_LOW] = 0;
tg->bps[WRITE][LIMIT_LOW] = 0;
tg->iops[READ][LIMIT_LOW] = 0;
tg->iops[WRITE][LIMIT_LOW] = 0;
blk_throtl_update_limit_valid(tg->td);
if (!tg->td->limit_valid[tg->td->limit_index])
throtl_upgrade_state(tg->td);
}
static void throtl_pd_free(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
del_timer_sync(&tg->service_queue.pending_timer);
kfree(tg);
}
static struct throtl_grp *
throtl_rb_first(struct throtl_service_queue *parent_sq)
{
/* Service tree is empty */
if (!parent_sq->nr_pending)
return NULL;
if (!parent_sq->first_pending)
parent_sq->first_pending = rb_first(&parent_sq->pending_tree);
if (parent_sq->first_pending)
return rb_entry_tg(parent_sq->first_pending);
return NULL;
}
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
rb_erase(n, root);
RB_CLEAR_NODE(n);
}
static void throtl_rb_erase(struct rb_node *n,
struct throtl_service_queue *parent_sq)
{
if (parent_sq->first_pending == n)
parent_sq->first_pending = NULL;
rb_erase_init(n, &parent_sq->pending_tree);
--parent_sq->nr_pending;
}
static void update_min_dispatch_time(struct throtl_service_queue *parent_sq)
{
struct throtl_grp *tg;
tg = throtl_rb_first(parent_sq);
if (!tg)
return;
parent_sq->first_pending_disptime = tg->disptime;
}
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;
unsigned long key = tg->disptime;
int left = 1;
while (*node != NULL) {
parent = *node;
__tg = rb_entry_tg(parent);
if (time_before(key, __tg->disptime))
node = &parent->rb_left;
else {
node = &parent->rb_right;
left = 0;
}
}
if (left)
parent_sq->first_pending = &tg->rb_node;
rb_link_node(&tg->rb_node, parent, node);
rb_insert_color(&tg->rb_node, &parent_sq->pending_tree);
}
static void __throtl_enqueue_tg(struct throtl_grp *tg)
{
tg_service_queue_add(tg);
tg->flags |= THROTL_TG_PENDING;
tg->service_queue.parent_sq->nr_pending++;
}
static void throtl_enqueue_tg(struct throtl_grp *tg)
{
if (!(tg->flags & THROTL_TG_PENDING))
__throtl_enqueue_tg(tg);
}
static void __throtl_dequeue_tg(struct throtl_grp *tg)
{
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)
{
if (tg->flags & THROTL_TG_PENDING)
__throtl_dequeue_tg(tg);
}
/* Call with queue lock held */
static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
unsigned long expires)
{
unsigned long max_expire = jiffies + 8 * sq_to_td(sq)->throtl_slice;
/*
* Since we are adjusting the throttle limit dynamically, the sleep
* time calculated according to previous limit might be invalid. It's
* possible the cgroup sleep time is very long and no other cgroups
* have IO running so notify the limit changes. Make sure the cgroup
* doesn't sleep too long to avoid the missed notification.
*/
if (time_after(expires, max_expire))
expires = max_expire;
mod_timer(&sq->pending_timer, expires);
throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
expires - jiffies, jiffies);
}
/**
* 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)
{
/* any pending children left? */
if (!sq->nr_pending)
return true;
update_min_dispatch_time(sq);
/* 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 + tg->td->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->bytes_disp[rw] = 0;
tg->io_disp[rw] = 0;
tg->slice_start[rw] = jiffies;
tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
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, tg->td->throtl_slice);
}
static inline void throtl_extend_slice(struct throtl_grp *tg, bool rw,
unsigned long jiffy_end)
{
tg->slice_end[rw] = roundup(jiffy_end, tg->td->throtl_slice);
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 */
static bool throtl_slice_used(struct throtl_grp *tg, bool rw)
{
if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
return false;
return 1;
}
/* Trim the used slices and adjust slice start accordingly */
static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
{
unsigned long nr_slices, time_elapsed, io_trim;
u64 bytes_trim, tmp;
BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]));
/*
* If bps are unlimited (-1), then time slice don't get
* renewed. Don't try to trim the slice if slice is used. A new
* slice will start when appropriate.
*/
if (throtl_slice_used(tg, rw))
return;
/*
* A bio has been dispatched. Also adjust slice_end. It might happen
* that initially cgroup limit was very low resulting in high
* slice_end, but later limit was bumped up and bio was dispached
* sooner, then we need to reduce slice_end. A high bogus slice_end
* is bad because it does not allow new slice to start.
*/
throtl_set_slice_end(tg, rw, jiffies + tg->td->throtl_slice);
time_elapsed = jiffies - tg->slice_start[rw];
nr_slices = time_elapsed / tg->td->throtl_slice;
if (!nr_slices)
return;
tmp = tg_bps_limit(tg, rw) * tg->td->throtl_slice * nr_slices;
do_div(tmp, HZ);
bytes_trim = tmp;
io_trim = (tg_iops_limit(tg, rw) * tg->td->throtl_slice * nr_slices) /
HZ;
if (!bytes_trim && !io_trim)
return;
if (tg->bytes_disp[rw] >= bytes_trim)
tg->bytes_disp[rw] -= bytes_trim;
else
tg->bytes_disp[rw] = 0;
if (tg->io_disp[rw] >= io_trim)
tg->io_disp[rw] -= io_trim;
else
tg->io_disp[rw] = 0;
tg->slice_start[rw] += nr_slices * tg->td->throtl_slice;
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,
unsigned long *wait)
{
bool rw = bio_data_dir(bio);
unsigned int io_allowed;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
u64 tmp;
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
/* Slice has just started. Consider one slice interval */
if (!jiffy_elapsed)
jiffy_elapsed_rnd = tg->td->throtl_slice;
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
/*
* jiffy_elapsed_rnd should not be a big value as minimum iops can be
* 1 then at max jiffy elapsed should be equivalent of 1 second as we
* will allow dispatch after 1 second and after that slice should
* have been trimmed.
*/
tmp = (u64)tg_iops_limit(tg, rw) * jiffy_elapsed_rnd;
do_div(tmp, HZ);
if (tmp > UINT_MAX)
io_allowed = UINT_MAX;
else
io_allowed = tmp;
if (tg->io_disp[rw] + 1 <= io_allowed) {
if (wait)
*wait = 0;
return true;
}
/* Calc approx time to dispatch */
jiffy_wait = ((tg->io_disp[rw] + 1) * HZ) / tg_iops_limit(tg, rw) + 1;
if (jiffy_wait > jiffy_elapsed)
jiffy_wait = jiffy_wait - jiffy_elapsed;
else
jiffy_wait = 1;
if (wait)
*wait = jiffy_wait;
return 0;
}
static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
unsigned long *wait)
{
bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes, tmp;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
unsigned int bio_size = throtl_bio_data_size(bio);
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
/* Slice has just started. Consider one slice interval */
if (!jiffy_elapsed)
jiffy_elapsed_rnd = tg->td->throtl_slice;
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
tmp = tg_bps_limit(tg, rw) * jiffy_elapsed_rnd;
do_div(tmp, HZ);
bytes_allowed = tmp;
if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
if (wait)
*wait = 0;
return true;
}
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
jiffy_wait = div64_u64(extra_bytes * HZ, tg_bps_limit(tg, rw));
if (!jiffy_wait)
jiffy_wait = 1;
/*
* This wait time is without taking into consideration the rounding
* up we did. Add that time also.
*/
jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
if (wait)
*wait = jiffy_wait;
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
*/
static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
unsigned long *wait)
{
bool rw = bio_data_dir(bio);
unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
/*
* Currently whole state machine of group depends on first bio
* queued in the group bio list. So one should not be calling
* this function with a different bio if there are other bios
* queued.
*/
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_limit(tg, rw) == U64_MAX &&
tg_iops_limit(tg, rw) == UINT_MAX) {
if (wait)
*wait = 0;
return true;
}
/*
* If previous slice expired, start a new one otherwise renew/extend
* existing slice to make sure it is at least throtl_slice interval
* long since now. New slice is started only for empty throttle group.
* If there is queued bio, that means there should be an active
* slice and it should be extended instead.
*/
if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
throtl_start_new_slice(tg, rw);
else {
if (time_before(tg->slice_end[rw],
jiffies + tg->td->throtl_slice))
throtl_extend_slice(tg, rw,
jiffies + tg->td->throtl_slice);
}
if (tg_with_in_bps_limit(tg, bio, &bps_wait) &&
tg_with_in_iops_limit(tg, bio, &iops_wait)) {
if (wait)
*wait = 0;
return 1;
}
max_wait = max(bps_wait, iops_wait);
if (wait)
*wait = max_wait;
if (time_before(tg->slice_end[rw], jiffies + max_wait))
throtl_extend_slice(tg, rw, jiffies + max_wait);
return 0;
}
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
unsigned int bio_size = throtl_bio_data_size(bio);
/* Charge the bio to the group */
tg->bytes_disp[rw] += bio_size;
tg->io_disp[rw]++;
tg->last_bytes_disp[rw] += bio_size;
tg->last_io_disp[rw]++;
/*
* BIO_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.
*/
if (!bio_flagged(bio, BIO_THROTTLED))
bio_set_flag(bio, BIO_THROTTLED);
}
/**
* 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);
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 *sq = &tg->service_queue;
unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
struct bio *bio;
bio = throtl_peek_queued(&sq->queued[READ]);
if (bio)
tg_may_dispatch(tg, bio, &read_wait);
bio = throtl_peek_queued(&sq->queued[WRITE]);
if (bio)
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);
tg->disptime = disptime;
throtl_enqueue_tg(tg);
/* see throtl_add_bio_tg() */
tg->flags &= ~THROTL_TG_WAS_EMPTY;
}
static void start_parent_slice_with_credit(struct throtl_grp *child_tg,
struct throtl_grp *parent_tg, bool rw)
{
if (throtl_slice_used(parent_tg, rw)) {
throtl_start_new_slice_with_credit(parent_tg, rw,
child_tg->slice_start[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);
/*
* 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 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;
struct bio *bio;
/* Try to dispatch 75% READS and 25% WRITES */
while ((bio = throtl_peek_queued(&sq->queued[READ])) &&
tg_may_dispatch(tg, bio, NULL)) {
tg_dispatch_one_bio(tg, bio_data_dir(bio));
nr_reads++;
if (nr_reads >= max_nr_reads)
break;
}
while ((bio = throtl_peek_queued(&sq->queued[WRITE])) &&
tg_may_dispatch(tg, bio, NULL)) {
tg_dispatch_one_bio(tg, bio_data_dir(bio));
nr_writes++;
if (nr_writes >= max_nr_writes)
break;
}
return nr_reads + nr_writes;
}
static int throtl_select_dispatch(struct throtl_service_queue *parent_sq)
{
unsigned int nr_disp = 0;
while (1) {
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);
nr_disp += throtl_dispatch_tg(tg);
if (sq->nr_queued[0] || sq->nr_queued[1])
tg_update_disptime(tg);
if (nr_disp >= throtl_quantum)
break;
}
return nr_disp;
}
static bool throtl_can_upgrade(struct throtl_data *td,
struct throtl_grp *this_tg);
/**
* 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(struct timer_list *t)
{
struct throtl_service_queue *sq = from_timer(sq, t, pending_timer);
struct throtl_grp *tg = sq_to_tg(sq);
struct throtl_data *td = sq_to_td(sq);
struct request_queue *q = td->queue;
struct throtl_service_queue *parent_sq;
bool dispatched;
int ret;
spin_lock_irq(q->queue_lock);
if (throtl_can_upgrade(td, NULL))
throtl_upgrade_state(td);
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;
}
if (throtl_schedule_next_dispatch(sq, false))
break;
/* this dispatch windows is still open, relax and repeat */
spin_unlock_irq(q->queue_lock);
cpu_relax();
spin_lock_irq(q->queue_lock);
}
if (!dispatched)
goto out_unlock;
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);
}
/**
* 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.
*/
static 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 (!bio_list_empty(&bio_list_on_stack)) {
blk_start_plug(&plug);
while((bio = bio_list_pop(&bio_list_on_stack)))
generic_make_request(bio);
blk_finish_plug(&plug);
}
}
static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
struct throtl_grp *tg = pd_to_tg(pd);
u64 v = *(u64 *)((void *)tg + off);
if (v == U64_MAX)
return 0;
return __blkg_prfill_u64(sf, pd, v);
}
static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
struct throtl_grp *tg = pd_to_tg(pd);
unsigned int v = *(unsigned int *)((void *)tg + off);
if (v == UINT_MAX)
return 0;
return __blkg_prfill_u64(sf, pd, v);
}
static int tg_print_conf_u64(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_u64,
&blkcg_policy_throtl, seq_cft(sf)->private, false);
return 0;
}
static int tg_print_conf_uint(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_conf_uint,
&blkcg_policy_throtl, seq_cft(sf)->private, false);
return 0;
}
static void tg_conf_updated(struct throtl_grp *tg, bool global)
{
struct throtl_service_queue *sq = &tg->service_queue;
struct cgroup_subsys_state *pos_css;
struct blkcg_gq *blkg;
throtl_log(&tg->service_queue,
"limit change rbps=%llu wbps=%llu riops=%u wiops=%u",
tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
tg_iops_limit(tg, READ), tg_iops_limit(tg, 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.
*/
blkg_for_each_descendant_pre(blkg, pos_css,
global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
struct throtl_grp *this_tg = blkg_to_tg(blkg);
struct throtl_grp *parent_tg;
tg_update_has_rules(this_tg);
/* ignore root/second level */
if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
!blkg->parent->parent)
continue;
parent_tg = blkg_to_tg(blkg->parent);
/*
* make sure all children has lower idle time threshold and
* higher latency target
*/
this_tg->idletime_threshold = min(this_tg->idletime_threshold,
parent_tg->idletime_threshold);
this_tg->latency_target = max(this_tg->latency_target,
parent_tg->latency_target);
}
/*
* We're already holding queue_lock and know @tg is valid. Let's
* apply the new config directly.
*
* Restart the slices for both READ and WRITES. It might happen
* that a group's limit are dropped suddenly and we don't want to
* account recently dispatched IO with new low rate.
*/
throtl_start_new_slice(tg, 0);
throtl_start_new_slice(tg, 1);
if (tg->flags & THROTL_TG_PENDING) {
tg_update_disptime(tg);
throtl_schedule_next_dispatch(sq->parent_sq, true);
}
}
static ssize_t tg_set_conf(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off, bool is_u64)
{
struct blkcg *blkcg = css_to_blkcg(of_css(of));
struct blkg_conf_ctx ctx;
struct throtl_grp *tg;
int ret;
u64 v;
ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
if (ret)
return ret;
ret = -EINVAL;
if (sscanf(ctx.body, "%llu", &v) != 1)
goto out_finish;
if (!v)
v = U64_MAX;
tg = blkg_to_tg(ctx.blkg);
if (is_u64)
*(u64 *)((void *)tg + of_cft(of)->private) = v;
else
*(unsigned int *)((void *)tg + of_cft(of)->private) = v;
tg_conf_updated(tg, false);
ret = 0;
out_finish:
blkg_conf_finish(&ctx);
return ret ?: nbytes;
}
static ssize_t tg_set_conf_u64(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
return tg_set_conf(of, buf, nbytes, off, true);
}
static ssize_t tg_set_conf_uint(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
return tg_set_conf(of, buf, nbytes, off, false);
}
static struct cftype throtl_legacy_files[] = {
{
.name = "throttle.read_bps_device",
.private = offsetof(struct throtl_grp, bps[READ][LIMIT_MAX]),
.seq_show = tg_print_conf_u64,
.write = tg_set_conf_u64,
},
{
.name = "throttle.write_bps_device",
.private = offsetof(struct throtl_grp, bps[WRITE][LIMIT_MAX]),
.seq_show = tg_print_conf_u64,
.write = tg_set_conf_u64,
},
{
.name = "throttle.read_iops_device",
.private = offsetof(struct throtl_grp, iops[READ][LIMIT_MAX]),
.seq_show = tg_print_conf_uint,
.write = tg_set_conf_uint,
},
{
.name = "throttle.write_iops_device",
.private = offsetof(struct throtl_grp, iops[WRITE][LIMIT_MAX]),
.seq_show = tg_print_conf_uint,
.write = tg_set_conf_uint,
},
{
.name = "throttle.io_service_bytes",
.private = (unsigned long)&blkcg_policy_throtl,
.seq_show = blkg_print_stat_bytes,
},
{
.name = "throttle.io_serviced",
.private = (unsigned long)&blkcg_policy_throtl,
.seq_show = blkg_print_stat_ios,
},
{ } /* terminate */
};
static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
struct throtl_grp *tg = pd_to_tg(pd);
const char *dname = blkg_dev_name(pd->blkg);
char bufs[4][21] = { "max", "max", "max", "max" };
u64 bps_dft;
unsigned int iops_dft;
char idle_time[26] = "";
char latency_time[26] = "";
if (!dname)
return 0;
if (off == LIMIT_LOW) {
bps_dft = 0;
iops_dft = 0;
} else {
bps_dft = U64_MAX;
iops_dft = UINT_MAX;
}
if (tg->bps_conf[READ][off] == bps_dft &&
tg->bps_conf[WRITE][off] == bps_dft &&
tg->iops_conf[READ][off] == iops_dft &&
tg->iops_conf[WRITE][off] == iops_dft &&
(off != LIMIT_LOW ||
(tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD &&
tg->latency_target_conf == DFL_LATENCY_TARGET)))
return 0;
if (tg->bps_conf[READ][off] != U64_MAX)
snprintf(bufs[0], sizeof(bufs[0]), "%llu",
tg->bps_conf[READ][off]);
if (tg->bps_conf[WRITE][off] != U64_MAX)
snprintf(bufs[1], sizeof(bufs[1]), "%llu",
tg->bps_conf[WRITE][off]);
if (tg->iops_conf[READ][off] != UINT_MAX)
snprintf(bufs[2], sizeof(bufs[2]), "%u",
tg->iops_conf[READ][off]);
if (tg->iops_conf[WRITE][off] != UINT_MAX)
snprintf(bufs[3], sizeof(bufs[3]), "%u",
tg->iops_conf[WRITE][off]);
if (off == LIMIT_LOW) {
if (tg->idletime_threshold_conf == ULONG_MAX)
strcpy(idle_time, " idle=max");
else
snprintf(idle_time, sizeof(idle_time), " idle=%lu",
tg->idletime_threshold_conf);
if (tg->latency_target_conf == ULONG_MAX)
strcpy(latency_time, " latency=max");
else
snprintf(latency_time, sizeof(latency_time),
" latency=%lu", tg->latency_target_conf);
}
seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n",
dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time,
latency_time);
return 0;
}
static int tg_print_limit(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), tg_prfill_limit,
&blkcg_policy_throtl, seq_cft(sf)->private, false);
return 0;
}
static ssize_t tg_set_limit(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct blkcg *blkcg = css_to_blkcg(of_css(of));
struct blkg_conf_ctx ctx;
struct throtl_grp *tg;
u64 v[4];
unsigned long idle_time;
unsigned long latency_time;
int ret;
int index = of_cft(of)->private;
ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx);
if (ret)
return ret;
tg = blkg_to_tg(ctx.blkg);
v[0] = tg->bps_conf[READ][index];
v[1] = tg->bps_conf[WRITE][index];
v[2] = tg->iops_conf[READ][index];
v[3] = tg->iops_conf[WRITE][index];
idle_time = tg->idletime_threshold_conf;
latency_time = tg->latency_target_conf;
while (true) {
char tok[27]; /* wiops=18446744073709551616 */
char *p;
u64 val = U64_MAX;
int len;
if (sscanf(ctx.body, "%26s%n", tok, &len) != 1)
break;
if (tok[0] == '\0')
break;
ctx.body += len;
ret = -EINVAL;
p = tok;
strsep(&p, "=");
if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
goto out_finish;
ret = -ERANGE;
if (!val)
goto out_finish;
ret = -EINVAL;
if (!strcmp(tok, "rbps"))
v[0] = val;
else if (!strcmp(tok, "wbps"))
v[1] = val;
else if (!strcmp(tok, "riops"))
v[2] = min_t(u64, val, UINT_MAX);
else if (!strcmp(tok, "wiops"))
v[3] = min_t(u64, val, UINT_MAX);
else if (off == LIMIT_LOW && !strcmp(tok, "idle"))
idle_time = val;
else if (off == LIMIT_LOW && !strcmp(tok, "latency"))
latency_time = val;
else
goto out_finish;
}
tg->bps_conf[READ][index] = v[0];
tg->bps_conf[WRITE][index] = v[1];
tg->iops_conf[READ][index] = v[2];
tg->iops_conf[WRITE][index] = v[3];
if (index == LIMIT_MAX) {
tg->bps[READ][index] = v[0];
tg->bps[WRITE][index] = v[1];
tg->iops[READ][index] = v[2];
tg->iops[WRITE][index] = v[3];
}
tg->bps[READ][LIMIT_LOW] = min(tg->bps_conf[READ][LIMIT_LOW],
tg->bps_conf[READ][LIMIT_MAX]);
tg->bps[WRITE][LIMIT_LOW] = min(tg->bps_conf[WRITE][LIMIT_LOW],
tg->bps_conf[WRITE][LIMIT_MAX]);
tg->iops[READ][LIMIT_LOW] = min(tg->iops_conf[READ][LIMIT_LOW],
tg->iops_conf[READ][LIMIT_MAX]);
tg->iops[WRITE][LIMIT_LOW] = min(tg->iops_conf[WRITE][LIMIT_LOW],
tg->iops_conf[WRITE][LIMIT_MAX]);
tg->idletime_threshold_conf = idle_time;
tg->latency_target_conf = latency_time;
/* force user to configure all settings for low limit */
if (!(tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW] ||
tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW]) ||
tg->idletime_threshold_conf == DFL_IDLE_THRESHOLD ||
tg->latency_target_conf == DFL_LATENCY_TARGET) {
tg->bps[READ][LIMIT_LOW] = 0;
tg->bps[WRITE][LIMIT_LOW] = 0;
tg->iops[READ][LIMIT_LOW] = 0;
tg->iops[WRITE][LIMIT_LOW] = 0;
tg->idletime_threshold = DFL_IDLE_THRESHOLD;
tg->latency_target = DFL_LATENCY_TARGET;
} else if (index == LIMIT_LOW) {
tg->idletime_threshold = tg->idletime_threshold_conf;
tg->latency_target = tg->latency_target_conf;
}
blk_throtl_update_limit_valid(tg->td);
if (tg->td->limit_valid[LIMIT_LOW]) {
if (index == LIMIT_LOW)
tg->td->limit_index = LIMIT_LOW;
} else
tg->td->limit_index = LIMIT_MAX;
tg_conf_updated(tg, index == LIMIT_LOW &&
tg->td->limit_valid[LIMIT_LOW]);
ret = 0;
out_finish:
blkg_conf_finish(&ctx);
return ret ?: nbytes;
}
static struct cftype throtl_files[] = {
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
{
.name = "low",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = tg_print_limit,
.write = tg_set_limit,
.private = LIMIT_LOW,
},
#endif
{
.name = "max",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = tg_print_limit,
.write = tg_set_limit,
.private = LIMIT_MAX,
},
{ } /* terminate */
};
static void throtl_shutdown_wq(struct request_queue *q)
{
struct throtl_data *td = q->td;
cancel_work_sync(&td->dispatch_work);
}
static struct blkcg_policy blkcg_policy_throtl = {
.dfl_cftypes = throtl_files,
.legacy_cftypes = throtl_legacy_files,
.pd_alloc_fn = throtl_pd_alloc,
.pd_init_fn = throtl_pd_init,
.pd_online_fn = throtl_pd_online,
.pd_offline_fn = throtl_pd_offline,
.pd_free_fn = throtl_pd_free,
};
static unsigned long __tg_last_low_overflow_time(struct throtl_grp *tg)
{
unsigned long rtime = jiffies, wtime = jiffies;
if (tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW])
rtime = tg->last_low_overflow_time[READ];
if (tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW])
wtime = tg->last_low_overflow_time[WRITE];
return min(rtime, wtime);
}
/* tg should not be an intermediate node */
static unsigned long tg_last_low_overflow_time(struct throtl_grp *tg)
{
struct throtl_service_queue *parent_sq;
struct throtl_grp *parent = tg;
unsigned long ret = __tg_last_low_overflow_time(tg);
while (true) {
parent_sq = parent->service_queue.parent_sq;
parent = sq_to_tg(parent_sq);
if (!parent)
break;
/*
* The parent doesn't have low limit, it always reaches low
* limit. Its overflow time is useless for children
*/
if (!parent->bps[READ][LIMIT_LOW] &&
!parent->iops[READ][LIMIT_LOW] &&
!parent->bps[WRITE][LIMIT_LOW] &&
!parent->iops[WRITE][LIMIT_LOW])
continue;
if (time_after(__tg_last_low_overflow_time(parent), ret))
ret = __tg_last_low_overflow_time(parent);
}
return ret;
}
static bool throtl_tg_is_idle(struct throtl_grp *tg)
{
/*
* cgroup is idle if:
* - single idle is too long, longer than a fixed value (in case user
* configure a too big threshold) or 4 times of idletime threshold
* - average think time is more than threshold
* - IO latency is largely below threshold
*/
unsigned long time;
bool ret;
time = min_t(unsigned long, MAX_IDLE_TIME, 4 * tg->idletime_threshold);
ret = tg->latency_target == DFL_LATENCY_TARGET ||
tg->idletime_threshold == DFL_IDLE_THRESHOLD ||
(ktime_get_ns() >> 10) - tg->last_finish_time > time ||
tg->avg_idletime > tg->idletime_threshold ||
(tg->latency_target && tg->bio_cnt &&
tg->bad_bio_cnt * 5 < tg->bio_cnt);
throtl_log(&tg->service_queue,
"avg_idle=%ld, idle_threshold=%ld, bad_bio=%d, total_bio=%d, is_idle=%d, scale=%d",
tg->avg_idletime, tg->idletime_threshold, tg->bad_bio_cnt,
tg->bio_cnt, ret, tg->td->scale);
return ret;
}
static bool throtl_tg_can_upgrade(struct throtl_grp *tg)
{
struct throtl_service_queue *sq = &tg->service_queue;
bool read_limit, write_limit;
/*
* if cgroup reaches low limit (if low limit is 0, the cgroup always
* reaches), it's ok to upgrade to next limit
*/
read_limit = tg->bps[READ][LIMIT_LOW] || tg->iops[READ][LIMIT_LOW];
write_limit = tg->bps[WRITE][LIMIT_LOW] || tg->iops[WRITE][LIMIT_LOW];
if (!read_limit && !write_limit)
return true;
if (read_limit && sq->nr_queued[READ] &&
(!write_limit || sq->nr_queued[WRITE]))
return true;
if (write_limit && sq->nr_queued[WRITE] &&
(!read_limit || sq->nr_queued[READ]))
return true;
if (time_after_eq(jiffies,
tg_last_low_overflow_time(tg) + tg->td->throtl_slice) &&
throtl_tg_is_idle(tg))
return true;
return false;
}
static bool throtl_hierarchy_can_upgrade(struct throtl_grp *tg)
{
while (true) {
if (throtl_tg_can_upgrade(tg))
return true;
tg = sq_to_tg(tg->service_queue.parent_sq);
if (!tg || !tg_to_blkg(tg)->parent)
return false;
}
return false;
}
static bool throtl_can_upgrade(struct throtl_data *td,
struct throtl_grp *this_tg)
{
struct cgroup_subsys_state *pos_css;
struct blkcg_gq *blkg;
if (td->limit_index != LIMIT_LOW)
return false;
if (time_before(jiffies, td->low_downgrade_time + td->throtl_slice))
return false;
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
if (tg == this_tg)
continue;
if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
continue;
if (!throtl_hierarchy_can_upgrade(tg)) {
rcu_read_unlock();
return false;
}
}
rcu_read_unlock();
return true;
}
static void throtl_upgrade_check(struct throtl_grp *tg)
{
unsigned long now = jiffies;
if (tg->td->limit_index != LIMIT_LOW)
return;
if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
return;
tg->last_check_time = now;
if (!time_after_eq(now,
__tg_last_low_overflow_time(tg) + tg->td->throtl_slice))
return;
if (throtl_can_upgrade(tg->td, NULL))
throtl_upgrade_state(tg->td);
}
static void throtl_upgrade_state(struct throtl_data *td)
{
struct cgroup_subsys_state *pos_css;
struct blkcg_gq *blkg;
throtl_log(&td->service_queue, "upgrade to max");
td->limit_index = LIMIT_MAX;
td->low_upgrade_time = jiffies;
td->scale = 0;
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq = &tg->service_queue;
tg->disptime = jiffies - 1;
throtl_select_dispatch(sq);
throtl_schedule_next_dispatch(sq, true);
}
rcu_read_unlock();
throtl_select_dispatch(&td->service_queue);
throtl_schedule_next_dispatch(&td->service_queue, true);
queue_work(kthrotld_workqueue, &td->dispatch_work);
}
static void throtl_downgrade_state(struct throtl_data *td, int new)
{
td->scale /= 2;
throtl_log(&td->service_queue, "downgrade, scale %d", td->scale);
if (td->scale) {
td->low_upgrade_time = jiffies - td->scale * td->throtl_slice;
return;
}
td->limit_index = new;
td->low_downgrade_time = jiffies;
}
static bool throtl_tg_can_downgrade(struct throtl_grp *tg)
{
struct throtl_data *td = tg->td;
unsigned long now = jiffies;
/*
* If cgroup is below low limit, consider downgrade and throttle other
* cgroups
*/
if (time_after_eq(now, td->low_upgrade_time + td->throtl_slice) &&
time_after_eq(now, tg_last_low_overflow_time(tg) +
td->throtl_slice) &&
(!throtl_tg_is_idle(tg) ||
!list_empty(&tg_to_blkg(tg)->blkcg->css.children)))
return true;
return false;
}
static bool throtl_hierarchy_can_downgrade(struct throtl_grp *tg)
{
while (true) {
if (!throtl_tg_can_downgrade(tg))
return false;
tg = sq_to_tg(tg->service_queue.parent_sq);
if (!tg || !tg_to_blkg(tg)->parent)
break;
}
return true;
}
static void throtl_downgrade_check(struct throtl_grp *tg)
{
uint64_t bps;
unsigned int iops;
unsigned long elapsed_time;
unsigned long now = jiffies;
if (tg->td->limit_index != LIMIT_MAX ||
!tg->td->limit_valid[LIMIT_LOW])
return;
if (!list_empty(&tg_to_blkg(tg)->blkcg->css.children))
return;
if (time_after(tg->last_check_time + tg->td->throtl_slice, now))
return;
elapsed_time = now - tg->last_check_time;
tg->last_check_time = now;
if (time_before(now, tg_last_low_overflow_time(tg) +
tg->td->throtl_slice))
return;
if (tg->bps[READ][LIMIT_LOW]) {
bps = tg->last_bytes_disp[READ] * HZ;
do_div(bps, elapsed_time);
if (bps >= tg->bps[READ][LIMIT_LOW])
tg->last_low_overflow_time[READ] = now;
}
if (tg->bps[WRITE][LIMIT_LOW]) {
bps = tg->last_bytes_disp[WRITE] * HZ;
do_div(bps, elapsed_time);
if (bps >= tg->bps[WRITE][LIMIT_LOW])
tg->last_low_overflow_time[WRITE] = now;
}
if (tg->iops[READ][LIMIT_LOW]) {
iops = tg->last_io_disp[READ] * HZ / elapsed_time;
if (iops >= tg->iops[READ][LIMIT_LOW])
tg->last_low_overflow_time[READ] = now;
}
if (tg->iops[WRITE][LIMIT_LOW]) {
iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
if (iops >= tg->iops[WRITE][LIMIT_LOW])
tg->last_low_overflow_time[WRITE] = now;
}
/*
* If cgroup is below low limit, consider downgrade and throttle other
* cgroups
*/
if (throtl_hierarchy_can_downgrade(tg))
throtl_downgrade_state(tg->td, LIMIT_LOW);
tg->last_bytes_disp[READ] = 0;
tg->last_bytes_disp[WRITE] = 0;
tg->last_io_disp[READ] = 0;
tg->last_io_disp[WRITE] = 0;
}
static void blk_throtl_update_idletime(struct throtl_grp *tg)
{
unsigned long now = ktime_get_ns() >> 10;
unsigned long last_finish_time = tg->last_finish_time;
if (now <= last_finish_time || last_finish_time == 0 ||
last_finish_time == tg->checked_last_finish_time)
return;
tg->avg_idletime = (tg->avg_idletime * 7 + now - last_finish_time) >> 3;
tg->checked_last_finish_time = last_finish_time;
}
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
static void throtl_update_latency_buckets(struct throtl_data *td)
{
struct avg_latency_bucket avg_latency[LATENCY_BUCKET_SIZE];
int i, cpu;
unsigned long last_latency = 0;
unsigned long latency;
if (!blk_queue_nonrot(td->queue))
return;
if (time_before(jiffies, td->last_calculate_time + HZ))
return;
td->last_calculate_time = jiffies;
memset(avg_latency, 0, sizeof(avg_latency));
for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
struct latency_bucket *tmp = &td->tmp_buckets[i];
for_each_possible_cpu(cpu) {
struct latency_bucket *bucket;
/* this isn't race free, but ok in practice */
bucket = per_cpu_ptr(td->latency_buckets, cpu);
tmp->total_latency += bucket[i].total_latency;
tmp->samples += bucket[i].samples;
bucket[i].total_latency = 0;
bucket[i].samples = 0;
}
if (tmp->samples >= 32) {
int samples = tmp->samples;
latency = tmp->total_latency;
tmp->total_latency = 0;
tmp->samples = 0;
latency /= samples;
if (latency == 0)
continue;
avg_latency[i].latency = latency;
}
}
for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
if (!avg_latency[i].latency) {
if (td->avg_buckets[i].latency < last_latency)
td->avg_buckets[i].latency = last_latency;
continue;
}
if (!td->avg_buckets[i].valid)
latency = avg_latency[i].latency;
else
latency = (td->avg_buckets[i].latency * 7 +
avg_latency[i].latency) >> 3;
td->avg_buckets[i].latency = max(latency, last_latency);
td->avg_buckets[i].valid = true;
last_latency = td->avg_buckets[i].latency;
}
for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
throtl_log(&td->service_queue,
"Latency bucket %d: latency=%ld, valid=%d", i,
td->avg_buckets[i].latency, td->avg_buckets[i].valid);
}
#else
static inline void throtl_update_latency_buckets(struct throtl_data *td)
{
}
#endif
static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
{
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
if (bio->bi_css) {
if (bio->bi_cg_private)
blkg_put(tg_to_blkg(bio->bi_cg_private));
bio->bi_cg_private = tg;
blkg_get(tg_to_blkg(tg));
}
blk_stat_set_issue(&bio->bi_issue_stat, bio_sectors(bio));
#endif
}
bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
struct bio *bio)
{
struct throtl_qnode *qn = NULL;
struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
struct throtl_service_queue *sq;
bool rw = bio_data_dir(bio);
bool throttled = false;
struct throtl_data *td = tg->td;
WARN_ON_ONCE(!rcu_read_lock_held());
/* see throtl_charge_bio() */
if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw])
goto out;
spin_lock_irq(q->queue_lock);
throtl_update_latency_buckets(td);
if (unlikely(blk_queue_bypass(q)))
goto out_unlock;
blk_throtl_assoc_bio(tg, bio);
blk_throtl_update_idletime(tg);
sq = &tg->service_queue;
again:
while (true) {
if (tg->last_low_overflow_time[rw] == 0)
tg->last_low_overflow_time[rw] = jiffies;
throtl_downgrade_check(tg);
throtl_upgrade_check(tg);
/* 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)) {
tg->last_low_overflow_time[rw] = jiffies;
if (throtl_can_upgrade(td, tg)) {
throtl_upgrade_state(td);
goto again;
}
break;
}
/* within limits, let's charge and dispatch directly */
throtl_charge_bio(tg, bio);
/*
* We need to trim slice even when bios are not being queued
* otherwise it might happen that a bio is not queued for
* a long time and slice keeps on extending and trim is not
* called for a long time. Now if limits are reduced suddenly
* we take into account all the IO dispatched so far at new
* low rate and * newly queued IO gets a really long dispatch
* time.
*
* So keep on trimming slice even if bio is not queued.
*/
throtl_trim_slice(tg, rw);
/*
* @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;
}
/* 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_iter.bi_size,
tg_bps_limit(tg, rw),
tg->io_disp[rw], tg_iops_limit(tg, rw),
sq->nr_queued[READ], sq->nr_queued[WRITE]);
tg->last_low_overflow_time[rw] = jiffies;
td->nr_queued[rw]++;
throtl_add_bio_tg(bio, qn, tg);
throttled = true;
/*
* 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:
spin_unlock_irq(q->queue_lock);
out:
bio_set_flag(bio, BIO_THROTTLED);
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
if (throttled || !td->track_bio_latency)
bio->bi_issue_stat.stat |= SKIP_LATENCY;
#endif
return throttled;
}
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
static void throtl_track_latency(struct throtl_data *td, sector_t size,
int op, unsigned long time)
{
struct latency_bucket *latency;
int index;
if (!td || td->limit_index != LIMIT_LOW || op != REQ_OP_READ ||
!blk_queue_nonrot(td->queue))
return;
index = request_bucket_index(size);
latency = get_cpu_ptr(td->latency_buckets);
latency[index].total_latency += time;
latency[index].samples++;
put_cpu_ptr(td->latency_buckets);
}
void blk_throtl_stat_add(struct request *rq, u64 time_ns)
{
struct request_queue *q = rq->q;
struct throtl_data *td = q->td;
throtl_track_latency(td, blk_stat_size(&rq->issue_stat),
req_op(rq), time_ns >> 10);
}
void blk_throtl_bio_endio(struct bio *bio)
{
struct throtl_grp *tg;
u64 finish_time_ns;
unsigned long finish_time;
unsigned long start_time;
unsigned long lat;
tg = bio->bi_cg_private;
if (!tg)
return;
bio->bi_cg_private = NULL;
finish_time_ns = ktime_get_ns();
tg->last_finish_time = finish_time_ns >> 10;
start_time = blk_stat_time(&bio->bi_issue_stat) >> 10;
finish_time = __blk_stat_time(finish_time_ns) >> 10;
if (!start_time || finish_time <= start_time) {
blkg_put(tg_to_blkg(tg));
return;
}
lat = finish_time - start_time;
/* this is only for bio based driver */
if (!(bio->bi_issue_stat.stat & SKIP_LATENCY))
throtl_track_latency(tg->td, blk_stat_size(&bio->bi_issue_stat),
bio_op(bio), lat);
if (tg->latency_target && lat >= tg->td->filtered_latency) {
int bucket;
unsigned int threshold;
bucket = request_bucket_index(
blk_stat_size(&bio->bi_issue_stat));
threshold = tg->td->avg_buckets[bucket].latency +
tg->latency_target;
if (lat > threshold)
tg->bad_bio_cnt++;
/*
* Not race free, could get wrong count, which means cgroups
* will be throttled
*/
tg->bio_cnt++;
}
if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
tg->bio_cnt /= 2;
tg->bad_bio_cnt /= 2;
}
blkg_put(tg_to_blkg(tg));
}
#endif
/*
* 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
*
* Dispatch all currently throttled bios on @q through ->make_request_fn().
*/
void blk_throtl_drain(struct request_queue *q)
__releases(q->queue_lock) __acquires(q->queue_lock)
{
struct throtl_data *td = q->td;
struct blkcg_gq *blkg;
struct cgroup_subsys_state *pos_css;
struct bio *bio;
int rw;
queue_lockdep_assert_held(q);
rcu_read_lock();
/*
* 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_css, td->queue->root_blkg)
tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
/* 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);
/* 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);
}
int blk_throtl_init(struct request_queue *q)
{
struct throtl_data *td;
int ret;
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
if (!td)
return -ENOMEM;
td->latency_buckets = __alloc_percpu(sizeof(struct latency_bucket) *
LATENCY_BUCKET_SIZE, __alignof__(u64));
if (!td->latency_buckets) {
kfree(td);
return -ENOMEM;
}
INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
throtl_service_queue_init(&td->service_queue);
q->td = td;
td->queue = q;
td->limit_valid[LIMIT_MAX] = true;
td->limit_index = LIMIT_MAX;
td->low_upgrade_time = jiffies;
td->low_downgrade_time = jiffies;
/* activate policy */
ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
if (ret) {
free_percpu(td->latency_buckets);
kfree(td);
}
return ret;
}
void blk_throtl_exit(struct request_queue *q)
{
BUG_ON(!q->td);
throtl_shutdown_wq(q);
blkcg_deactivate_policy(q, &blkcg_policy_throtl);
free_percpu(q->td->latency_buckets);
kfree(q->td);
}
void blk_throtl_register_queue(struct request_queue *q)
{
struct throtl_data *td;
int i;
td = q->td;
BUG_ON(!td);
if (blk_queue_nonrot(q)) {
td->throtl_slice = DFL_THROTL_SLICE_SSD;
td->filtered_latency = LATENCY_FILTERED_SSD;
} else {
td->throtl_slice = DFL_THROTL_SLICE_HD;
td->filtered_latency = LATENCY_FILTERED_HD;
for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
td->avg_buckets[i].latency = DFL_HD_BASELINE_LATENCY;
}
#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
/* if no low limit, use previous default */
td->throtl_slice = DFL_THROTL_SLICE_HD;
#endif
td->track_bio_latency = !q->mq_ops && !q->request_fn;
if (!td->track_bio_latency)
blk_stat_enable_accounting(q);
}
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
ssize_t blk_throtl_sample_time_show(struct request_queue *q, char *page)
{
if (!q->td)
return -EINVAL;
return sprintf(page, "%u\n", jiffies_to_msecs(q->td->throtl_slice));
}
ssize_t blk_throtl_sample_time_store(struct request_queue *q,
const char *page, size_t count)
{
unsigned long v;
unsigned long t;
if (!q->td)
return -EINVAL;
if (kstrtoul(page, 10, &v))
return -EINVAL;
t = msecs_to_jiffies(v);
if (t == 0 || t > MAX_THROTL_SLICE)
return -EINVAL;
q->td->throtl_slice = t;
return count;
}
#endif
static int __init throtl_init(void)
{
kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0);
if (!kthrotld_workqueue)
panic("Failed to create kthrotld\n");
return blkcg_policy_register(&blkcg_policy_throtl);
}
module_init(throtl_init);