blkio: Core implementation of throttle policy

o Actual implementation of throttling policy in block layer. Currently it
  implements READ and WRITE bytes per second throttling logic. IOPS throttling
  comes in later patches.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Vivek Goyal 2010-09-15 17:06:35 -04:00 committed by Jens Axboe
parent 4c9eefa16c
commit e43473b7f2
7 changed files with 979 additions and 3 deletions

View File

@ -77,6 +77,18 @@ config BLK_DEV_INTEGRITY
T10/SCSI Data Integrity Field or the T13/ATA External Path
Protection. If in doubt, say N.
config BLK_DEV_THROTTLING
bool "Block layer bio throttling support"
depends on BLK_CGROUP=y && EXPERIMENTAL
default n
---help---
Block layer bio throttling support. It can be used to limit
the IO rate to a device. IO rate policies are per cgroup and
one needs to mount and use blkio cgroup controller for creating
cgroups and specifying per device IO rate policies.
See Documentation/cgroups/blkio-controller.txt for more information.
endif # BLOCK
config BLOCK_COMPAT

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@ -9,6 +9,7 @@ obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
obj-$(CONFIG_BLK_DEV_BSG) += bsg.o
obj-$(CONFIG_BLK_CGROUP) += blk-cgroup.o
obj-$(CONFIG_BLK_DEV_THROTTLING) += blk-throttle.o
obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o

View File

@ -382,6 +382,7 @@ void blk_sync_queue(struct request_queue *q)
del_timer_sync(&q->unplug_timer);
del_timer_sync(&q->timeout);
cancel_work_sync(&q->unplug_work);
throtl_shutdown_timer_wq(q);
}
EXPORT_SYMBOL(blk_sync_queue);
@ -459,6 +460,8 @@ void blk_cleanup_queue(struct request_queue *q)
if (q->elevator)
elevator_exit(q->elevator);
blk_throtl_exit(q);
blk_put_queue(q);
}
EXPORT_SYMBOL(blk_cleanup_queue);
@ -515,6 +518,11 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
return NULL;
}
if (blk_throtl_init(q)) {
kmem_cache_free(blk_requestq_cachep, q);
return NULL;
}
setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
laptop_mode_timer_fn, (unsigned long) q);
init_timer(&q->unplug_timer);
@ -1522,6 +1530,15 @@ static inline void __generic_make_request(struct bio *bio)
goto end_io;
}
blk_throtl_bio(q, &bio);
/*
* If bio = NULL, bio has been throttled and will be submitted
* later.
*/
if (!bio)
break;
trace_block_bio_queue(q, bio);
ret = q->make_request_fn(q, bio);
@ -2580,6 +2597,13 @@ int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
}
EXPORT_SYMBOL(kblockd_schedule_work);
int kblockd_schedule_delayed_work(struct request_queue *q,
struct delayed_work *dwork, unsigned long delay)
{
return queue_delayed_work(kblockd_workqueue, dwork, delay);
}
EXPORT_SYMBOL(kblockd_schedule_delayed_work);
int __init blk_dev_init(void)
{
BUILD_BUG_ON(__REQ_NR_BITS > 8 *

909
block/blk-throttle.c Normal file
View File

@ -0,0 +1,909 @@
/*
* 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-cgroup.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 100ms slice and after that slice is renewed */
static unsigned long throtl_slice = HZ/10; /* 100 ms */
struct throtl_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned int count;
unsigned long min_disptime;
};
#define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \
.count = 0, .min_disptime = 0}
#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
struct throtl_grp {
/* List of throtl groups on the request queue*/
struct hlist_node tg_node;
/* active throtl group service_tree member */
struct rb_node rb_node;
/*
* 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;
struct blkio_group blkg;
atomic_t ref;
unsigned int flags;
/* Two lists for READ and WRITE */
struct bio_list bio_lists[2];
/* Number of queued bios on READ and WRITE lists */
unsigned int nr_queued[2];
/* bytes per second rate limits */
uint64_t bps[2];
/* Number of bytes disptached in current slice */
uint64_t bytes_disp[2];
/* When did we start a new slice */
unsigned long slice_start[2];
unsigned long slice_end[2];
};
struct throtl_data
{
/* List of throtl groups */
struct hlist_head tg_list;
/* service tree for active throtl groups */
struct throtl_rb_root tg_service_tree;
struct throtl_grp root_tg;
struct request_queue *queue;
/* Total Number of queued bios on READ and WRITE lists */
unsigned int nr_queued[2];
/*
* number of total undestroyed groups (excluding root group)
*/
unsigned int nr_undestroyed_grps;
/* Work for dispatching throttled bios */
struct delayed_work throtl_work;
};
enum tg_state_flags {
THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */
};
#define THROTL_TG_FNS(name) \
static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \
{ \
(tg)->flags |= (1 << THROTL_TG_FLAG_##name); \
} \
static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \
{ \
(tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \
} \
static inline int throtl_tg_##name(const struct throtl_grp *tg) \
{ \
return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \
}
THROTL_TG_FNS(on_rr);
#define throtl_log_tg(td, tg, fmt, args...) \
blk_add_trace_msg((td)->queue, "throtl %s " fmt, \
blkg_path(&(tg)->blkg), ##args); \
#define throtl_log(td, fmt, args...) \
blk_add_trace_msg((td)->queue, "throtl " fmt, ##args)
static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg)
{
if (blkg)
return container_of(blkg, struct throtl_grp, blkg);
return NULL;
}
static inline int total_nr_queued(struct throtl_data *td)
{
return (td->nr_queued[0] + td->nr_queued[1]);
}
static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
{
atomic_inc(&tg->ref);
return tg;
}
static void throtl_put_tg(struct throtl_grp *tg)
{
BUG_ON(atomic_read(&tg->ref) <= 0);
if (!atomic_dec_and_test(&tg->ref))
return;
kfree(tg);
}
static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td,
struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
struct throtl_grp *tg = NULL;
void *key = td;
struct backing_dev_info *bdi = &td->queue->backing_dev_info;
unsigned int major, minor;
/*
* TODO: Speed up blkiocg_lookup_group() by maintaining a radix
* tree of blkg (instead of traversing through hash list all
* the time.
*/
tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key));
/* Fill in device details for root group */
if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
tg->blkg.dev = MKDEV(major, minor);
goto done;
}
if (tg)
goto done;
tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node);
if (!tg)
goto done;
INIT_HLIST_NODE(&tg->tg_node);
RB_CLEAR_NODE(&tg->rb_node);
bio_list_init(&tg->bio_lists[0]);
bio_list_init(&tg->bio_lists[1]);
/*
* Take the initial reference that will be released on destroy
* This can be thought of a joint reference by cgroup and
* request queue which will be dropped by either request queue
* exit or cgroup deletion path depending on who is exiting first.
*/
atomic_set(&tg->ref, 1);
/* Add group onto cgroup list */
sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td,
MKDEV(major, minor), BLKIO_POLICY_THROTL);
tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev);
tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev);
hlist_add_head(&tg->tg_node, &td->tg_list);
td->nr_undestroyed_grps++;
done:
return tg;
}
static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
{
struct cgroup *cgroup;
struct throtl_grp *tg = NULL;
rcu_read_lock();
cgroup = task_cgroup(current, blkio_subsys_id);
tg = throtl_find_alloc_tg(td, cgroup);
if (!tg)
tg = &td->root_tg;
rcu_read_unlock();
return tg;
}
static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root)
{
/* Service tree is empty */
if (!root->count)
return NULL;
if (!root->left)
root->left = rb_first(&root->rb);
if (root->left)
return rb_entry_tg(root->left);
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_rb_root *root)
{
if (root->left == n)
root->left = NULL;
rb_erase_init(n, &root->rb);
--root->count;
}
static void update_min_dispatch_time(struct throtl_rb_root *st)
{
struct throtl_grp *tg;
tg = throtl_rb_first(st);
if (!tg)
return;
st->min_disptime = tg->disptime;
}
static void
tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg)
{
struct rb_node **node = &st->rb.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)
st->left = &tg->rb_node;
rb_link_node(&tg->rb_node, parent, node);
rb_insert_color(&tg->rb_node, &st->rb);
}
static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
{
struct throtl_rb_root *st = &td->tg_service_tree;
tg_service_tree_add(st, tg);
throtl_mark_tg_on_rr(tg);
st->count++;
}
static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg)
{
if (!throtl_tg_on_rr(tg))
__throtl_enqueue_tg(td, tg);
}
static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
{
throtl_rb_erase(&tg->rb_node, &td->tg_service_tree);
throtl_clear_tg_on_rr(tg);
}
static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg)
{
if (throtl_tg_on_rr(tg))
__throtl_dequeue_tg(td, tg);
}
static void throtl_schedule_next_dispatch(struct throtl_data *td)
{
struct throtl_rb_root *st = &td->tg_service_tree;
/*
* If there are more bios pending, schedule more work.
*/
if (!total_nr_queued(td))
return;
BUG_ON(!st->count);
update_min_dispatch_time(st);
if (time_before_eq(st->min_disptime, jiffies))
throtl_schedule_delayed_work(td->queue, 0);
else
throtl_schedule_delayed_work(td->queue,
(st->min_disptime - jiffies));
}
static inline void
throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
{
tg->bytes_disp[rw] = 0;
tg->slice_start[rw] = jiffies;
tg->slice_end[rw] = jiffies + throtl_slice;
throtl_log_tg(td, tg, "[%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_extend_slice(struct throtl_data *td,
struct throtl_grp *tg, bool rw, unsigned long jiffy_end)
{
tg->slice_end[rw] = roundup(jiffy_end, throtl_slice);
throtl_log_tg(td, tg, "[%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_data *td, struct throtl_grp *tg, bool rw)
{
if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw]))
return 0;
return 1;
}
/* Trim the used slices and adjust slice start accordingly */
static inline void
throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
{
unsigned long nr_slices, bytes_trim, time_elapsed;
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(td, tg, rw))
return;
time_elapsed = jiffies - tg->slice_start[rw];
nr_slices = time_elapsed / throtl_slice;
if (!nr_slices)
return;
bytes_trim = (tg->bps[rw] * throtl_slice * nr_slices)/HZ;
if (!bytes_trim)
return;
if (tg->bytes_disp[rw] >= bytes_trim)
tg->bytes_disp[rw] -= bytes_trim;
else
tg->bytes_disp[rw] = 0;
tg->slice_start[rw] += nr_slices * throtl_slice;
throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%lu"
" start=%lu end=%lu jiffies=%lu",
rw == READ ? 'R' : 'W', nr_slices, bytes_trim,
tg->slice_start[rw], tg->slice_end[rw], jiffies);
}
/*
* 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_data *td, struct throtl_grp *tg,
struct bio *bio, unsigned long *wait)
{
bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
/*
* 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->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
/* If tg->bps = -1, then BW is unlimited */
if (tg->bps[rw] == -1) {
if (wait)
*wait = 0;
return 1;
}
/*
* 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.
*/
if (throtl_slice_used(td, tg, rw))
throtl_start_new_slice(td, tg, rw);
else {
if (time_before(tg->slice_end[rw], jiffies + throtl_slice))
throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
}
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
/* Slice has just started. Consider one slice interval */
if (!jiffy_elapsed)
jiffy_elapsed_rnd = throtl_slice;
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
bytes_allowed = (tg->bps[rw] * jiffies_to_msecs(jiffy_elapsed_rnd))
/ MSEC_PER_SEC;
if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
if (wait)
*wait = 0;
return 1;
}
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[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;
if (time_before(tg->slice_end[rw], jiffies + jiffy_wait))
throtl_extend_slice(td, tg, rw, jiffies + jiffy_wait);
return 0;
}
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
bool sync = bio->bi_rw & REQ_SYNC;
/* Charge the bio to the group */
tg->bytes_disp[rw] += bio->bi_size;
/*
* TODO: This will take blkg->stats_lock. Figure out a way
* to avoid this cost.
*/
blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync);
}
static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg,
struct bio *bio)
{
bool rw = bio_data_dir(bio);
bio_list_add(&tg->bio_lists[rw], bio);
/* Take a bio reference on tg */
throtl_ref_get_tg(tg);
tg->nr_queued[rw]++;
td->nr_queued[rw]++;
throtl_enqueue_tg(td, tg);
}
static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
{
unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
struct bio *bio;
if ((bio = bio_list_peek(&tg->bio_lists[READ])))
tg_may_dispatch(td, tg, bio, &read_wait);
if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
tg_may_dispatch(td, tg, bio, &write_wait);
min_wait = min(read_wait, write_wait);
disptime = jiffies + min_wait;
/*
* If group is already on active tree, then update dispatch time
* only if it is lesser than existing dispatch time. Otherwise
* always update the dispatch time
*/
if (throtl_tg_on_rr(tg) && time_before(disptime, tg->disptime))
return;
/* Update dispatch time */
throtl_dequeue_tg(td, tg);
tg->disptime = disptime;
throtl_enqueue_tg(td, tg);
}
static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg,
bool rw, struct bio_list *bl)
{
struct bio *bio;
bio = bio_list_pop(&tg->bio_lists[rw]);
tg->nr_queued[rw]--;
/* Drop bio reference on tg */
throtl_put_tg(tg);
BUG_ON(td->nr_queued[rw] <= 0);
td->nr_queued[rw]--;
throtl_charge_bio(tg, bio);
bio_list_add(bl, bio);
bio->bi_rw |= REQ_THROTTLED;
throtl_trim_slice(td, tg, rw);
}
static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
struct bio_list *bl)
{
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 - nr_reads;
struct bio *bio;
/* Try to dispatch 75% READS and 25% WRITES */
while ((bio = bio_list_peek(&tg->bio_lists[READ]))
&& tg_may_dispatch(td, tg, bio, NULL)) {
tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
nr_reads++;
if (nr_reads >= max_nr_reads)
break;
}
while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
&& tg_may_dispatch(td, tg, bio, NULL)) {
tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
nr_writes++;
if (nr_writes >= max_nr_writes)
break;
}
return nr_reads + nr_writes;
}
static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl)
{
unsigned int nr_disp = 0;
struct throtl_grp *tg;
struct throtl_rb_root *st = &td->tg_service_tree;
while (1) {
tg = throtl_rb_first(st);
if (!tg)
break;
if (time_before(jiffies, tg->disptime))
break;
throtl_dequeue_tg(td, tg);
nr_disp += throtl_dispatch_tg(td, tg, bl);
if (tg->nr_queued[0] || tg->nr_queued[1]) {
tg_update_disptime(td, tg);
throtl_enqueue_tg(td, tg);
}
if (nr_disp >= throtl_quantum)
break;
}
return nr_disp;
}
/* Dispatch throttled bios. Should be called without queue lock held. */
static int throtl_dispatch(struct request_queue *q)
{
struct throtl_data *td = q->td;
unsigned int nr_disp = 0;
struct bio_list bio_list_on_stack;
struct bio *bio;
spin_lock_irq(q->queue_lock);
if (!total_nr_queued(td))
goto out;
bio_list_init(&bio_list_on_stack);
throtl_log(td, "dispatch nr_queued=%lu read=%u write=%u",
total_nr_queued(td), td->nr_queued[READ],
td->nr_queued[WRITE]);
nr_disp = throtl_select_dispatch(td, &bio_list_on_stack);
if (nr_disp)
throtl_log(td, "bios disp=%u", nr_disp);
throtl_schedule_next_dispatch(td);
out:
spin_unlock_irq(q->queue_lock);
/*
* If we dispatched some requests, unplug the queue to make sure
* immediate dispatch
*/
if (nr_disp) {
while((bio = bio_list_pop(&bio_list_on_stack)))
generic_make_request(bio);
blk_unplug(q);
}
return nr_disp;
}
void blk_throtl_work(struct work_struct *work)
{
struct throtl_data *td = container_of(work, struct throtl_data,
throtl_work.work);
struct request_queue *q = td->queue;
throtl_dispatch(q);
}
/* Call with queue lock held */
void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay)
{
struct throtl_data *td = q->td;
struct delayed_work *dwork = &td->throtl_work;
if (total_nr_queued(td) > 0) {
/*
* We might have a work scheduled to be executed in future.
* Cancel that and schedule a new one.
*/
__cancel_delayed_work(dwork);
kblockd_schedule_delayed_work(q, dwork, delay);
throtl_log(td, "schedule work. delay=%lu jiffies=%lu",
delay, jiffies);
}
}
EXPORT_SYMBOL(throtl_schedule_delayed_work);
static void
throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
{
/* Something wrong if we are trying to remove same group twice */
BUG_ON(hlist_unhashed(&tg->tg_node));
hlist_del_init(&tg->tg_node);
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
throtl_put_tg(tg);
td->nr_undestroyed_grps--;
}
static void throtl_release_tgs(struct throtl_data *td)
{
struct hlist_node *pos, *n;
struct throtl_grp *tg;
hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
/*
* If cgroup removal path got to blk_group first and removed
* it from cgroup list, then it will take care of destroying
* cfqg also.
*/
if (!blkiocg_del_blkio_group(&tg->blkg))
throtl_destroy_tg(td, tg);
}
}
static void throtl_td_free(struct throtl_data *td)
{
kfree(td);
}
/*
* Blk cgroup controller notification saying that blkio_group object is being
* delinked as associated cgroup object is going away. That also means that
* no new IO will come in this group. So get rid of this group as soon as
* any pending IO in the group is finished.
*
* This function is called under rcu_read_lock(). key is the rcu protected
* pointer. That means "key" is a valid throtl_data pointer as long as we are
* rcu read lock.
*
* "key" was fetched from blkio_group under blkio_cgroup->lock. That means
* it should not be NULL as even if queue was going away, cgroup deltion
* path got to it first.
*/
void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg)
{
unsigned long flags;
struct throtl_data *td = key;
spin_lock_irqsave(td->queue->queue_lock, flags);
throtl_destroy_tg(td, tg_of_blkg(blkg));
spin_unlock_irqrestore(td->queue->queue_lock, flags);
}
static void throtl_update_blkio_group_read_bps (struct blkio_group *blkg,
u64 read_bps)
{
tg_of_blkg(blkg)->bps[READ] = read_bps;
}
static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg,
u64 write_bps)
{
tg_of_blkg(blkg)->bps[WRITE] = write_bps;
}
void throtl_shutdown_timer_wq(struct request_queue *q)
{
struct throtl_data *td = q->td;
cancel_delayed_work_sync(&td->throtl_work);
}
static struct blkio_policy_type blkio_policy_throtl = {
.ops = {
.blkio_unlink_group_fn = throtl_unlink_blkio_group,
.blkio_update_group_read_bps_fn =
throtl_update_blkio_group_read_bps,
.blkio_update_group_write_bps_fn =
throtl_update_blkio_group_write_bps,
},
};
int blk_throtl_bio(struct request_queue *q, struct bio **biop)
{
struct throtl_data *td = q->td;
struct throtl_grp *tg;
struct bio *bio = *biop;
bool rw = bio_data_dir(bio), update_disptime = true;
if (bio->bi_rw & REQ_THROTTLED) {
bio->bi_rw &= ~REQ_THROTTLED;
return 0;
}
spin_lock_irq(q->queue_lock);
tg = throtl_get_tg(td);
if (tg->nr_queued[rw]) {
/*
* There is already another bio queued in same dir. No
* need to update dispatch time.
*/
update_disptime = false;
goto queue_bio;
}
/* Bio is with-in rate limit of group */
if (tg_may_dispatch(td, tg, bio, NULL)) {
throtl_charge_bio(tg, bio);
goto out;
}
queue_bio:
throtl_log_tg(td, tg, "[%c] bio. disp=%u sz=%u bps=%llu"
" queued=%d/%d", rw == READ ? 'R' : 'W',
tg->bytes_disp[rw], bio->bi_size, tg->bps[rw],
tg->nr_queued[READ], tg->nr_queued[WRITE]);
throtl_add_bio_tg(q->td, tg, bio);
*biop = NULL;
if (update_disptime) {
tg_update_disptime(td, tg);
throtl_schedule_next_dispatch(td);
}
out:
spin_unlock_irq(q->queue_lock);
return 0;
}
int blk_throtl_init(struct request_queue *q)
{
struct throtl_data *td;
struct throtl_grp *tg;
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
if (!td)
return -ENOMEM;
INIT_HLIST_HEAD(&td->tg_list);
td->tg_service_tree = THROTL_RB_ROOT;
/* Init root group */
tg = &td->root_tg;
INIT_HLIST_NODE(&tg->tg_node);
RB_CLEAR_NODE(&tg->rb_node);
bio_list_init(&tg->bio_lists[0]);
bio_list_init(&tg->bio_lists[1]);
/* Practically unlimited BW */
tg->bps[0] = tg->bps[1] = -1;
atomic_set(&tg->ref, 1);
INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work);
rcu_read_lock();
blkiocg_add_blkio_group(&blkio_root_cgroup, &tg->blkg, (void *)td,
0, BLKIO_POLICY_THROTL);
rcu_read_unlock();
/* Attach throtl data to request queue */
td->queue = q;
q->td = td;
return 0;
}
void blk_throtl_exit(struct request_queue *q)
{
struct throtl_data *td = q->td;
bool wait = false;
BUG_ON(!td);
throtl_shutdown_timer_wq(q);
spin_lock_irq(q->queue_lock);
throtl_release_tgs(td);
blkiocg_del_blkio_group(&td->root_tg.blkg);
/* If there are other groups */
if (td->nr_undestroyed_grps >= 1)
wait = true;
spin_unlock_irq(q->queue_lock);
/*
* Wait for tg->blkg->key accessors to exit their grace periods.
* Do this wait only if there are other undestroyed groups out
* there (other than root group). This can happen if cgroup deletion
* path claimed the responsibility of cleaning up a group before
* queue cleanup code get to the group.
*
* Do not call synchronize_rcu() unconditionally as there are drivers
* which create/delete request queue hundreds of times during scan/boot
* and synchronize_rcu() can take significant time and slow down boot.
*/
if (wait)
synchronize_rcu();
throtl_td_free(td);
}
static int __init throtl_init(void)
{
blkio_policy_register(&blkio_policy_throtl);
return 0;
}
module_init(throtl_init);

View File

@ -130,6 +130,8 @@ enum rq_flag_bits {
/* bio only flags */
__REQ_UNPLUG, /* unplug the immediately after submission */
__REQ_RAHEAD, /* read ahead, can fail anytime */
__REQ_THROTTLED, /* This bio has already been subjected to
* throttling rules. Don't do it again. */
/* request only flags */
__REQ_SORTED, /* elevator knows about this request */
@ -172,6 +174,7 @@ enum rq_flag_bits {
#define REQ_UNPLUG (1 << __REQ_UNPLUG)
#define REQ_RAHEAD (1 << __REQ_RAHEAD)
#define REQ_THROTTLED (1 << __REQ_THROTTLED)
#define REQ_SORTED (1 << __REQ_SORTED)
#define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)

View File

@ -371,6 +371,11 @@ struct request_queue
#if defined(CONFIG_BLK_DEV_BSG)
struct bsg_class_device bsg_dev;
#endif
#ifdef CONFIG_BLK_DEV_THROTTLING
/* Throttle data */
struct throtl_data *td;
#endif
};
#define QUEUE_FLAG_CLUSTER 0 /* cluster several segments into 1 */
@ -1131,6 +1136,7 @@ static inline void put_dev_sector(Sector p)
struct work_struct;
int kblockd_schedule_work(struct request_queue *q, struct work_struct *work);
int kblockd_schedule_delayed_work(struct request_queue *q, struct delayed_work *dwork, unsigned long delay);
#ifdef CONFIG_BLK_CGROUP
/*
@ -1174,6 +1180,24 @@ static inline uint64_t rq_io_start_time_ns(struct request *req)
}
#endif
#ifdef CONFIG_BLK_DEV_THROTTLING
extern int blk_throtl_init(struct request_queue *q);
extern void blk_throtl_exit(struct request_queue *q);
extern int blk_throtl_bio(struct request_queue *q, struct bio **bio);
extern void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay);
extern void throtl_shutdown_timer_wq(struct request_queue *q);
#else /* CONFIG_BLK_DEV_THROTTLING */
static inline int blk_throtl_bio(struct request_queue *q, struct bio **bio)
{
return 0;
}
static inline int blk_throtl_init(struct request_queue *q) { return 0; }
static inline int blk_throtl_exit(struct request_queue *q) { return 0; }
static inline void throtl_schedule_delayed_work(struct request_queue *q, unsigned long delay) {}
static inline void throtl_shutdown_timer_wq(struct request_queue *q) {}
#endif /* CONFIG_BLK_DEV_THROTTLING */
#define MODULE_ALIAS_BLOCKDEV(major,minor) \
MODULE_ALIAS("block-major-" __stringify(major) "-" __stringify(minor))
#define MODULE_ALIAS_BLOCKDEV_MAJOR(major) \

View File

@ -634,11 +634,14 @@ config BLK_CGROUP
Currently, CFQ IO scheduler uses it to recognize task groups and
control disk bandwidth allocation (proportional time slice allocation)
to such task groups.
to such task groups. It is also used by bio throttling logic in
block layer to implement upper limit in IO rates on a device.
This option only enables generic Block IO controller infrastructure.
One needs to also enable actual IO controlling logic in CFQ for it
to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
One needs to also enable actual IO controlling logic/policy. For
enabling proportional weight division of disk bandwidth in CFQ seti
CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
CONFIG_BLK_THROTTLE=y.
See Documentation/cgroups/blkio-controller.txt for more information.