linux/block/blk-throttle.c
Yu Kuai 1beabab88e blk-throttle: fix lower control under super low iops limit
User will configure allowed iops limit in 1s, and calculate_io_allowed()
will calculate allowed iops in the slice by:

limit * HZ / throtl_slice

However, if limit is quite low, the result can be 0, then
allowed IO in the slice is 0, this will cause missing dispatch and
control will be lower than limit.

For example, set iops_limit to 5 with HD disk, and test will found that
iops will be 3.

This is usually not a big deal, because user will unlikely to configure
such low iops limit, however, this is still a problem in the extreme
scene.

Fix the problem by making sure the wait time calculated by
tg_within_iops_limit() should allow at least one IO to be dispatched.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240618062108.3680835-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-06-28 14:55:02 -06:00

1711 lines
45 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 "blk.h"
#include "blk-cgroup-rwstat.h"
#include "blk-stat.h"
#include "blk-throttle.h"
/* Max dispatch from a group in 1 round */
#define THROTL_GRP_QUANTUM 8
/* Total max dispatch from all groups in one round */
#define 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)
/* A workqueue to queue throttle related work */
static struct workqueue_struct *kthrotld_workqueue;
#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
/* 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 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;
bool track_bio_latency;
};
static void throtl_pending_timer_fn(struct timer_list *t);
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);
}
static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return U64_MAX;
return tg->bps[rw];
}
static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
{
struct blkcg_gq *blkg = tg_to_blkg(tg);
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return UINT_MAX;
return tg->iops[rw];
}
#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->css, "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;
struct bio *bio;
if (list_empty(queued))
return NULL;
qn = list_first_entry(queued, struct throtl_qnode, node);
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;
struct bio *bio;
if (list_empty(queued))
return NULL;
qn = list_first_entry(queued, struct throtl_qnode, node);
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[READ]);
INIT_LIST_HEAD(&sq->queued[WRITE]);
sq->pending_tree = RB_ROOT_CACHED;
timer_setup(&sq->pending_timer, throtl_pending_timer_fn, 0);
}
static struct blkg_policy_data *throtl_pd_alloc(struct gendisk *disk,
struct blkcg *blkcg, gfp_t gfp)
{
struct throtl_grp *tg;
int rw;
tg = kzalloc_node(sizeof(*tg), gfp, disk->node_id);
if (!tg)
return NULL;
if (blkg_rwstat_init(&tg->stat_bytes, gfp))
goto err_free_tg;
if (blkg_rwstat_init(&tg->stat_ios, gfp))
goto err_exit_stat_bytes;
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] = U64_MAX;
tg->bps[WRITE] = U64_MAX;
tg->iops[READ] = UINT_MAX;
tg->iops[WRITE] = UINT_MAX;
return &tg->pd;
err_exit_stat_bytes:
blkg_rwstat_exit(&tg->stat_bytes);
err_free_tg:
kfree(tg);
return NULL;
}
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 a parent group, summary bps of
* parent group and its subtree groups 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);
int rw;
for (rw = READ; rw <= WRITE; rw++) {
tg->has_rules_iops[rw] =
(parent_tg && parent_tg->has_rules_iops[rw]) ||
tg_iops_limit(tg, rw) != UINT_MAX;
tg->has_rules_bps[rw] =
(parent_tg && parent_tg->has_rules_bps[rw]) ||
tg_bps_limit(tg, rw) != U64_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 throtl_pd_free(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
del_timer_sync(&tg->service_queue.pending_timer);
blkg_rwstat_exit(&tg->stat_bytes);
blkg_rwstat_exit(&tg->stat_ios);
kfree(tg);
}
static struct throtl_grp *
throtl_rb_first(struct throtl_service_queue *parent_sq)
{
struct rb_node *n;
n = rb_first_cached(&parent_sq->pending_tree);
WARN_ON_ONCE(!n);
if (!n)
return NULL;
return rb_entry_tg(n);
}
static void throtl_rb_erase(struct rb_node *n,
struct throtl_service_queue *parent_sq)
{
rb_erase_cached(n, &parent_sq->pending_tree);
RB_CLEAR_NODE(n);
}
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_root.rb_node;
struct rb_node *parent = NULL;
struct throtl_grp *__tg;
unsigned long key = tg->disptime;
bool leftmost = true;
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;
leftmost = false;
}
}
rb_link_node(&tg->rb_node, parent, node);
rb_insert_color_cached(&tg->rb_node, &parent_sq->pending_tree,
leftmost);
}
static void throtl_enqueue_tg(struct throtl_grp *tg)
{
if (!(tg->flags & THROTL_TG_PENDING)) {
tg_service_queue_add(tg);
tg->flags |= THROTL_TG_PENDING;
tg->service_queue.parent_sq->nr_pending++;
}
}
static void throtl_dequeue_tg(struct throtl_grp *tg)
{
if (tg->flags & THROTL_TG_PENDING) {
struct throtl_service_queue *parent_sq =
tg->service_queue.parent_sq;
throtl_rb_erase(&tg->rb_node, parent_sq);
--parent_sq->nr_pending;
tg->flags &= ~THROTL_TG_PENDING;
}
}
/* 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;
tg->carryover_bytes[rw] = 0;
tg->carryover_ios[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(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,
bool clear_carryover)
{
tg->bytes_disp[rw] = 0;
tg->io_disp[rw] = 0;
tg->slice_start[rw] = jiffies;
tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
if (clear_carryover) {
tg->carryover_bytes[rw] = 0;
tg->carryover_ios[rw] = 0;
}
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)
{
throtl_set_slice_end(tg, rw, jiffy_end);
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 true;
}
static unsigned int calculate_io_allowed(u32 iops_limit,
unsigned long jiffy_elapsed)
{
unsigned int io_allowed;
u64 tmp;
/*
* jiffy_elapsed 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)iops_limit * jiffy_elapsed;
do_div(tmp, HZ);
if (tmp > UINT_MAX)
io_allowed = UINT_MAX;
else
io_allowed = tmp;
return io_allowed;
}
static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
{
/*
* Can result be wider than 64 bits?
* We check against 62, not 64, due to ilog2 truncation.
*/
if (ilog2(bps_limit) + ilog2(jiffy_elapsed) - ilog2(HZ) > 62)
return U64_MAX;
return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
}
/* Trim the used slices and adjust slice start accordingly */
static inline void throtl_trim_slice(struct throtl_grp *tg, bool rw)
{
unsigned long time_elapsed;
long long bytes_trim;
int io_trim;
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 dispatched
* 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 = rounddown(jiffies - tg->slice_start[rw],
tg->td->throtl_slice);
if (!time_elapsed)
return;
bytes_trim = calculate_bytes_allowed(tg_bps_limit(tg, rw),
time_elapsed) +
tg->carryover_bytes[rw];
io_trim = calculate_io_allowed(tg_iops_limit(tg, rw), time_elapsed) +
tg->carryover_ios[rw];
if (bytes_trim <= 0 && io_trim <= 0)
return;
tg->carryover_bytes[rw] = 0;
if ((long long)tg->bytes_disp[rw] >= bytes_trim)
tg->bytes_disp[rw] -= bytes_trim;
else
tg->bytes_disp[rw] = 0;
tg->carryover_ios[rw] = 0;
if ((int)tg->io_disp[rw] >= io_trim)
tg->io_disp[rw] -= io_trim;
else
tg->io_disp[rw] = 0;
tg->slice_start[rw] += time_elapsed;
throtl_log(&tg->service_queue,
"[%c] trim slice nr=%lu bytes=%lld io=%d start=%lu end=%lu jiffies=%lu",
rw == READ ? 'R' : 'W', time_elapsed / tg->td->throtl_slice,
bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw],
jiffies);
}
static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
{
unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
u64 bps_limit = tg_bps_limit(tg, rw);
u32 iops_limit = tg_iops_limit(tg, rw);
/*
* If config is updated while bios are still throttled, calculate and
* accumulate how many bytes/ios are waited across changes. And
* carryover_bytes/ios will be used to calculate new wait time under new
* configuration.
*/
if (bps_limit != U64_MAX)
tg->carryover_bytes[rw] +=
calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
tg->bytes_disp[rw];
if (iops_limit != UINT_MAX)
tg->carryover_ios[rw] +=
calculate_io_allowed(iops_limit, jiffy_elapsed) -
tg->io_disp[rw];
}
static void tg_update_carryover(struct throtl_grp *tg)
{
if (tg->service_queue.nr_queued[READ])
__tg_update_carryover(tg, READ);
if (tg->service_queue.nr_queued[WRITE])
__tg_update_carryover(tg, WRITE);
/* see comments in struct throtl_grp for meaning of these fields. */
throtl_log(&tg->service_queue, "%s: %lld %lld %d %d\n", __func__,
tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
}
static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
u32 iops_limit)
{
bool rw = bio_data_dir(bio);
int io_allowed;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
if (iops_limit == UINT_MAX) {
return 0;
}
jiffy_elapsed = jiffies - tg->slice_start[rw];
/* Round up to the next throttle slice, wait time must be nonzero */
jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
tg->carryover_ios[rw];
if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed)
return 0;
/* Calc approx time to dispatch */
jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
/* make sure at least one io can be dispatched after waiting */
jiffy_wait = max(jiffy_wait, HZ / iops_limit + 1);
return jiffy_wait;
}
static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
u64 bps_limit)
{
bool rw = bio_data_dir(bio);
long long bytes_allowed;
u64 extra_bytes;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
unsigned int bio_size = throtl_bio_data_size(bio);
/* no need to throttle if this bio's bytes have been accounted */
if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) {
return 0;
}
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);
bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
tg->carryover_bytes[rw];
if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
return 0;
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
jiffy_wait = div64_u64(extra_bytes * HZ, bps_limit);
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);
return jiffy_wait;
}
/*
* 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;
u64 bps_limit = tg_bps_limit(tg, rw);
u32 iops_limit = tg_iops_limit(tg, rw);
/*
* 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 ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
tg->flags & THROTL_TG_CANCELING) {
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, true);
else {
if (time_before(tg->slice_end[rw],
jiffies + tg->td->throtl_slice))
throtl_extend_slice(tg, rw,
jiffies + tg->td->throtl_slice);
}
bps_wait = tg_within_bps_limit(tg, bio, bps_limit);
iops_wait = tg_within_iops_limit(tg, bio, iops_limit);
if (bps_wait + iops_wait == 0) {
if (wait)
*wait = 0;
return true;
}
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 false;
}
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 */
if (!bio_flagged(bio, BIO_BPS_THROTTLED)) {
tg->bytes_disp[rw] += bio_size;
tg->last_bytes_disp[rw] += bio_size;
}
tg->io_disp[rw]++;
tg->last_io_disp[rw]++;
}
/**
* 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
* cleared 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_rb_erase(&tg->rb_node, tg->service_queue.parent_sq);
tg->disptime = disptime;
tg_service_queue_add(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 {
bio_set_flag(bio, BIO_BPS_THROTTLED);
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, READ);
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, WRITE);
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;
struct throtl_service_queue *sq;
if (!parent_sq->nr_pending)
break;
tg = throtl_rb_first(parent_sq);
if (!tg)
break;
if (time_before(jiffies, tg->disptime))
break;
nr_disp += throtl_dispatch_tg(tg);
sq = &tg->service_queue;
if (sq->nr_queued[READ] || sq->nr_queued[WRITE])
tg_update_disptime(tg);
else
throtl_dequeue_tg(tg);
if (nr_disp >= THROTL_QUANTUM)
break;
}
return nr_disp;
}
/**
* throtl_pending_timer_fn - timer function for service_queue->pending_timer
* @t: the pending_timer member of 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 throtl_service_queue *parent_sq;
struct request_queue *q;
bool dispatched;
int ret;
/* throtl_data may be gone, so figure out request queue by blkg */
if (tg)
q = tg->pd.blkg->q;
else
q = td->queue;
spin_lock_irq(&q->queue_lock);
if (!q->root_blkg)
goto out_unlock;
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 issuing */
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 bios reach the bio_lists[]
* of throtl_data->service_queue. Those bios 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)))
submit_bio_noacct_nocheck(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));
rcu_read_lock();
/*
* 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);
tg_update_has_rules(this_tg);
/* ignore root/second level */
if (!cgroup_subsys_on_dfl(io_cgrp_subsys) || !blkg->parent ||
!blkg->parent->parent)
continue;
}
rcu_read_unlock();
/*
* 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, READ, false);
throtl_start_new_slice(tg, WRITE, false);
if (tg->flags & THROTL_TG_PENDING) {
tg_update_disptime(tg);
throtl_schedule_next_dispatch(sq->parent_sq, true);
}
}
static int blk_throtl_init(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct throtl_data *td;
int ret;
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
if (!td)
return -ENOMEM;
INIT_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
throtl_service_queue_init(&td->service_queue);
/*
* Freeze queue before activating policy, to synchronize with IO path,
* which is protected by 'q_usage_counter'.
*/
blk_mq_freeze_queue(disk->queue);
blk_mq_quiesce_queue(disk->queue);
q->td = td;
td->queue = q;
/* activate policy */
ret = blkcg_activate_policy(disk, &blkcg_policy_throtl);
if (ret) {
q->td = NULL;
kfree(td);
goto out;
}
if (blk_queue_nonrot(q))
td->throtl_slice = DFL_THROTL_SLICE_SSD;
else
td->throtl_slice = DFL_THROTL_SLICE_HD;
td->track_bio_latency = !queue_is_mq(q);
if (!td->track_bio_latency)
blk_stat_enable_accounting(q);
out:
blk_mq_unquiesce_queue(disk->queue);
blk_mq_unfreeze_queue(disk->queue);
return ret;
}
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;
blkg_conf_init(&ctx, buf);
ret = blkg_conf_open_bdev(&ctx);
if (ret)
goto out_finish;
if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
ret = blk_throtl_init(ctx.bdev->bd_disk);
if (ret)
goto out_finish;
}
ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
if (ret)
goto out_finish;
ret = -EINVAL;
if (sscanf(ctx.body, "%llu", &v) != 1)
goto out_finish;
if (!v)
v = U64_MAX;
tg = blkg_to_tg(ctx.blkg);
tg_update_carryover(tg);
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_exit(&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 int tg_print_rwstat(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
blkg_prfill_rwstat, &blkcg_policy_throtl,
seq_cft(sf)->private, true);
return 0;
}
static u64 tg_prfill_rwstat_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat_sample sum;
blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_throtl, off,
&sum);
return __blkg_prfill_rwstat(sf, pd, &sum);
}
static int tg_print_rwstat_recursive(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
tg_prfill_rwstat_recursive, &blkcg_policy_throtl,
seq_cft(sf)->private, true);
return 0;
}
static struct cftype throtl_legacy_files[] = {
{
.name = "throttle.read_bps_device",
.private = offsetof(struct throtl_grp, bps[READ]),
.seq_show = tg_print_conf_u64,
.write = tg_set_conf_u64,
},
{
.name = "throttle.write_bps_device",
.private = offsetof(struct throtl_grp, bps[WRITE]),
.seq_show = tg_print_conf_u64,
.write = tg_set_conf_u64,
},
{
.name = "throttle.read_iops_device",
.private = offsetof(struct throtl_grp, iops[READ]),
.seq_show = tg_print_conf_uint,
.write = tg_set_conf_uint,
},
{
.name = "throttle.write_iops_device",
.private = offsetof(struct throtl_grp, iops[WRITE]),
.seq_show = tg_print_conf_uint,
.write = tg_set_conf_uint,
},
{
.name = "throttle.io_service_bytes",
.private = offsetof(struct throtl_grp, stat_bytes),
.seq_show = tg_print_rwstat,
},
{
.name = "throttle.io_service_bytes_recursive",
.private = offsetof(struct throtl_grp, stat_bytes),
.seq_show = tg_print_rwstat_recursive,
},
{
.name = "throttle.io_serviced",
.private = offsetof(struct throtl_grp, stat_ios),
.seq_show = tg_print_rwstat,
},
{
.name = "throttle.io_serviced_recursive",
.private = offsetof(struct throtl_grp, stat_ios),
.seq_show = tg_print_rwstat_recursive,
},
{ } /* 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);
u64 bps_dft;
unsigned int iops_dft;
if (!dname)
return 0;
bps_dft = U64_MAX;
iops_dft = UINT_MAX;
if (tg->bps[READ] == bps_dft &&
tg->bps[WRITE] == bps_dft &&
tg->iops[READ] == iops_dft &&
tg->iops[WRITE] == iops_dft)
return 0;
seq_printf(sf, "%s", dname);
if (tg->bps[READ] == U64_MAX)
seq_printf(sf, " rbps=max");
else
seq_printf(sf, " rbps=%llu", tg->bps[READ]);
if (tg->bps[WRITE] == U64_MAX)
seq_printf(sf, " wbps=max");
else
seq_printf(sf, " wbps=%llu", tg->bps[WRITE]);
if (tg->iops[READ] == UINT_MAX)
seq_printf(sf, " riops=max");
else
seq_printf(sf, " riops=%u", tg->iops[READ]);
if (tg->iops[WRITE] == UINT_MAX)
seq_printf(sf, " wiops=max");
else
seq_printf(sf, " wiops=%u", tg->iops[WRITE]);
seq_printf(sf, "\n");
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];
int ret;
blkg_conf_init(&ctx, buf);
ret = blkg_conf_open_bdev(&ctx);
if (ret)
goto out_finish;
if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
ret = blk_throtl_init(ctx.bdev->bd_disk);
if (ret)
goto out_finish;
}
ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
if (ret)
goto out_finish;
tg = blkg_to_tg(ctx.blkg);
tg_update_carryover(tg);
v[0] = tg->bps[READ];
v[1] = tg->bps[WRITE];
v[2] = tg->iops[READ];
v[3] = tg->iops[WRITE];
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") && val > 1)
v[0] = val;
else if (!strcmp(tok, "wbps") && val > 1)
v[1] = val;
else if (!strcmp(tok, "riops") && val > 1)
v[2] = min_t(u64, val, UINT_MAX);
else if (!strcmp(tok, "wiops") && val > 1)
v[3] = min_t(u64, val, UINT_MAX);
else
goto out_finish;
}
tg->bps[READ] = v[0];
tg->bps[WRITE] = v[1];
tg->iops[READ] = v[2];
tg->iops[WRITE] = v[3];
tg_conf_updated(tg, false);
ret = 0;
out_finish:
blkg_conf_exit(&ctx);
return ret ?: nbytes;
}
static struct cftype throtl_files[] = {
{
.name = "max",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = tg_print_limit,
.write = tg_set_limit,
},
{ } /* terminate */
};
static void throtl_shutdown_wq(struct request_queue *q)
{
struct throtl_data *td = q->td;
cancel_work_sync(&td->dispatch_work);
}
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_free_fn = throtl_pd_free,
};
void blk_throtl_cancel_bios(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct cgroup_subsys_state *pos_css;
struct blkcg_gq *blkg;
if (!blk_throtl_activated(q))
return;
spin_lock_irq(&q->queue_lock);
/*
* queue_lock is held, rcu lock is not needed here technically.
* However, rcu lock is still held to emphasize that following
* path need RCU protection and to prevent warning from lockdep.
*/
rcu_read_lock();
blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq = &tg->service_queue;
/*
* Set the flag to make sure throtl_pending_timer_fn() won't
* stop until all throttled bios are dispatched.
*/
tg->flags |= THROTL_TG_CANCELING;
/*
* Do not dispatch cgroup without THROTL_TG_PENDING or cgroup
* will be inserted to service queue without THROTL_TG_PENDING
* set in tg_update_disptime below. Then IO dispatched from
* child in tg_dispatch_one_bio will trigger double insertion
* and corrupt the tree.
*/
if (!(tg->flags & THROTL_TG_PENDING))
continue;
/*
* Update disptime after setting the above flag to make sure
* throtl_select_dispatch() won't exit without dispatching.
*/
tg_update_disptime(tg);
throtl_schedule_pending_timer(sq, jiffies + 1);
}
rcu_read_unlock();
spin_unlock_irq(&q->queue_lock);
}
bool __blk_throtl_bio(struct bio *bio)
{
struct request_queue *q = bdev_get_queue(bio->bi_bdev);
struct blkcg_gq *blkg = bio->bi_blkg;
struct throtl_qnode *qn = NULL;
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq;
bool rw = bio_data_dir(bio);
bool throttled = false;
struct throtl_data *td = tg->td;
rcu_read_lock();
spin_lock_irq(&q->queue_lock);
sq = &tg->service_queue;
while (true) {
if (tg->last_low_overflow_time[rw] == 0)
tg->last_low_overflow_time[rw] = jiffies;
/* 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;
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) {
bio_set_flag(bio, BIO_BPS_THROTTLED);
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);
rcu_read_unlock();
return throttled;
}
void blk_throtl_exit(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
if (!blk_throtl_activated(q))
return;
del_timer_sync(&q->td->service_queue.pending_timer);
throtl_shutdown_wq(q);
blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
kfree(q->td);
}
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);