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SubjectRe: [PATCH 2/3] i/o bandwidth controller infrastructure
Carl Henrik Lunde wrote:
> Did you consider using token bucket instead of this (leaky bucket?)?
>
> I've attached a patch which implements token bucket. Although not as
> precise as the leaky bucket the performance is better at high bandwidth
> streaming loads.
>
> The leaky bucket stops at around 53 MB/s while token bucket works for
> up to 64 MB/s. The baseline (no cgroups) is 66 MB/s.
>
> benchmark:
> two streaming readers (fio) with block size 128k, bucket size 4 MB
> 90% of the bandwidth was allocated to one process, the other gets 10%
>
> bw-limit: actual bw algorithm bw1 bw2
> 5 MiB/s: 5.0 MiB/s leaky_bucket 0.5 4.5
> 5 MiB/s: 5.2 MiB/s token_bucket 0.6 4.6
> 10 MiB/s: 10.0 MiB/s leaky_bucket 1.0 9.0
> 10 MiB/s: 10.3 MiB/s token_bucket 1.0 9.2
> 15 MiB/s: 15.0 MiB/s leaky_bucket 1.5 13.5
> 15 MiB/s: 15.4 MiB/s token_bucket 1.5 13.8
> 20 MiB/s: 19.9 MiB/s leaky_bucket 2.0 17.9
> 20 MiB/s: 20.5 MiB/s token_bucket 2.1 18.4
> 25 MiB/s: 24.4 MiB/s leaky_bucket 2.5 21.9
> 25 MiB/s: 25.6 MiB/s token_bucket 2.6 23.0
> 30 MiB/s: 29.2 MiB/s leaky_bucket 3.0 26.2
> 30 MiB/s: 30.7 MiB/s token_bucket 3.1 27.7
> 35 MiB/s: 34.3 MiB/s leaky_bucket 3.4 30.9
> 35 MiB/s: 35.9 MiB/s token_bucket 3.6 32.3
> 40 MiB/s: 39.7 MiB/s leaky_bucket 3.9 35.8
> 40 MiB/s: 41.0 MiB/s token_bucket 4.1 36.9
> 45 MiB/s: 44.0 MiB/s leaky_bucket 4.3 39.7
> 45 MiB/s: 46.1 MiB/s token_bucket 4.6 41.5
> 50 MiB/s: 47.9 MiB/s leaky_bucket 4.7 43.2
> 50 MiB/s: 51.0 MiB/s token_bucket 5.1 45.9
> 55 MiB/s: 50.5 MiB/s leaky_bucket 5.0 45.5
> 55 MiB/s: 56.2 MiB/s token_bucket 5.6 50.5
> 60 MiB/s: 52.9 MiB/s leaky_bucket 5.2 47.7
> 60 MiB/s: 61.0 MiB/s token_bucket 6.1 54.9
> 65 MiB/s: 53.0 MiB/s leaky_bucket 5.4 47.6
> 65 MiB/s: 63.7 MiB/s token_bucket 6.6 57.1
> 70 MiB/s: 53.8 MiB/s leaky_bucket 5.5 48.4
> 70 MiB/s: 64.1 MiB/s token_bucket 7.1 57.0

Carl,

based on your token bucket solution I've implemented a run-time leaky
bucket / token bucket switcher:

# leaky bucket #
echo 0 > /cgroups/foo/blockio.throttling_strategy
# token bucket #
echo 1 > /cgroups/foo/blockio.throttling_strategy

The -rc of the new io-throttle patch 2/3 is below, 1/3 and 3/3 are the
same as patchset version 3, even if documentation must be updated. It
would be great if you could review the patch, in particular the
token_bucket() implementation and repeat your tests.

The all-in-one patch is available here:
http://download.systemimager.org/~arighi/linux/patches/io-throttle/cgroup-io-throttle-v4-rc1.patch

I also did some quick tests similar to yours, the benchmark I've used is
available here as well:
http://download.systemimager.org/~arighi/linux/patches/io-throttle/benchmark/iobw.c

= Results =
I/O scheduler: cfq
filesystem: ext3
Command: ionice -c 1 -n 0 iobw -direct 2 4m 32m
Bucket size: 4MiB

testing 2 parallel streams, chunk_size 4096KiB, data_size 32768KiB

=== no throttling ===
testing 2 parallel streams, chunk_size 4096KiB, data_size 32768KiB
[task 2] time: 2.929, bw: 10742 KiB/s (WRITE)
[task 2] time: 2.878, bw: 10742 KiB/s (READ )
[task 1] time: 2.377, bw: 13671 KiB/s (WRITE)
[task 1] time: 3.979, bw: 7812 KiB/s (READ )
[parent 0] time: 6.397, bw: 19531 KiB/s (TOTAL)

=== bandwidth limit: 4MiB/s (leaky bucket) ===
[task 2] time: 15.880, bw: 1953 KiB/s (WRITE)
[task 2] time: 14.278, bw: 1953 KiB/s (READ )
[task 1] time: 14.711, bw: 1953 KiB/s (WRITE)
[task 1] time: 16.563, bw: 1953 KiB/s (READ )
[parent 0] time: 31.316, bw: 3906 KiB/s (TOTAL)

=== bandwidth limit: 4MiB/s (token bucket) ===
[task 2] time: 11.864, bw: 1953 KiB/s (WRITE)
[task 2] time: 15.958, bw: 1953 KiB/s (READ )
[task 1] time: 19.233, bw: 976 KiB/s (WRITE)
[task 1] time: 12.643, bw: 1953 KiB/s (READ )
[parent 0] time: 31.917, bw: 3906 KiB/s (TOTAL)

=== bandwidth limit: 8MiB/s (leaky bucket) ===
[task 2] time: 7.198, bw: 3906 KiB/s (WRITE)
[task 2] time: 8.012, bw: 3906 KiB/s (READ )
[task 1] time: 7.891, bw: 3906 KiB/s (WRITE)
[task 1] time: 7.846, bw: 3906 KiB/s (READ )
[parent 0] time: 15.780, bw: 7812 KiB/s (TOTAL)

=== bandwidth limit: 8MiB/s (token bucket) ===
[task 1] time: 6.996, bw: 3906 KiB/s (WRITE)
[task 1] time: 6.529, bw: 4882 KiB/s (READ )
[task 2] time: 10.341, bw: 2929 KiB/s (WRITE)
[task 2] time: 5.681, bw: 4882 KiB/s (READ )
[parent 0] time: 16.079, bw: 7812 KiB/s (TOTAL)

=== bandwidth limit: 12MiB/s (leaky bucket) ===
[task 2] time: 4.992, bw: 5859 KiB/s (WRITE)
[task 2] time: 5.077, bw: 5859 KiB/s (READ )
[task 1] time: 5.500, bw: 5859 KiB/s (WRITE)
[task 1] time: 5.061, bw: 5859 KiB/s (READ )
[parent 0] time: 10.603, bw: 11718 KiB/s (TOTAL)

=== bandwidth limit: 12MiB/s (token bucket) ===
[task 1] time: 5.057, bw: 5859 KiB/s (WRITE)
[task 1] time: 4.329, bw: 6835 KiB/s (READ )
[task 2] time: 5.771, bw: 4882 KiB/s (WRITE)
[task 2] time: 4.961, bw: 5859 KiB/s (READ )
[parent 0] time: 10.786, bw: 11718 KiB/s (TOTAL)

=== bandwidth limit: 16MiB/s (leaky bucket) ===
[task 1] time: 3.737, bw: 7812 KiB/s (WRITE)
[task 1] time: 3.988, bw: 7812 KiB/s (READ )
[task 2] time: 4.043, bw: 7812 KiB/s (WRITE)
[task 2] time: 3.954, bw: 7812 KiB/s (READ )
[parent 0] time: 8.040, bw: 15625 KiB/s (TOTAL)

=== bandwidth limit: 16MiB/s (token bucket) ===
[task 1] time: 3.224, bw: 9765 KiB/s (WRITE)
[task 1] time: 3.550, bw: 8789 KiB/s (READ )
[task 2] time: 5.085, bw: 5859 KiB/s (WRITE)
[task 2] time: 3.033, bw: 10742 KiB/s (READ )
[parent 0] time: 8.160, bw: 15625 KiB/s (TOTAL)

=== bandwidth limit: 20MiB/s (leaky bucket) ===
[task 1] time: 3.265, bw: 9765 KiB/s (WRITE)
[task 1] time: 3.339, bw: 9765 KiB/s (READ )
[task 2] time: 3.001, bw: 10742 KiB/s (WRITE)
[task 2] time: 3.840, bw: 7812 KiB/s (READ )
[parent 0] time: 6.884, bw: 18554 KiB/s (TOTAL)

=== bandwidth limit: 20MiB/s (token bucket) ===
[task 1] time: 2.897, bw: 10742 KiB/s (WRITE)
[task 1] time: 3.071, bw: 9765 KiB/s (READ )
[task 2] time: 3.697, bw: 8789 KiB/s (WRITE)
[task 2] time: 2.925, bw: 10742 KiB/s (READ )
[parent 0] time: 6.657, bw: 19531 KiB/s (TOTAL)

=== bandwidth limit: 24MiB/s (leaky bucket) ===
[task 1] time: 2.283, bw: 13671 KiB/s (WRITE)
[task 1] time: 3.626, bw: 8789 KiB/s (READ )
[task 2] time: 3.892, bw: 7812 KiB/s (WRITE)
[task 2] time: 2.774, bw: 11718 KiB/s (READ )
[parent 0] time: 6.724, bw: 18554 KiB/s (TOTAL)

=== bandwidth limit: 24MiB/s (token bucket) ===
[task 2] time: 3.215, bw: 9765 KiB/s (WRITE)
[task 2] time: 2.767, bw: 11718 KiB/s (READ )
[task 1] time: 2.615, bw: 11718 KiB/s (WRITE)
[task 1] time: 3.958, bw: 7812 KiB/s (READ )
[parent 0] time: 6.610, bw: 19531 KiB/s (TOTAL)

In conclusion, results seem to confirm that leaky bucket is more precise
(more smoothed) than token bucket; token bucket, instead, is better in
terms of efficiency when approaching to the disk's I/O physical limit,
as the theory claims.

It would be also interesting to test how token bucket performance
changes using different bucket size values. I'll do more accurate tests
ASAP.

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
---
block/Makefile | 2 +
block/blk-io-throttle.c | 490 +++++++++++++++++++++++++++++++++++++++
include/linux/blk-io-throttle.h | 12 +
include/linux/cgroup_subsys.h | 6 +
init/Kconfig | 10 +
5 files changed, 520 insertions(+), 0 deletions(-)

diff --git a/block/Makefile b/block/Makefile
index 5a43c7d..8dec69b 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -14,3 +14,5 @@ obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o

obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
+
+obj-$(CONFIG_CGROUP_IO_THROTTLE) += blk-io-throttle.o
diff --git a/block/blk-io-throttle.c b/block/blk-io-throttle.c
new file mode 100644
index 0000000..c6af273
--- /dev/null
+++ b/block/blk-io-throttle.c
@@ -0,0 +1,490 @@
+/*
+ * blk-io-throttle.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ * Copyright (C) 2008 Andrea Righi <righi.andrea@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cgroup.h>
+#include <linux/slab.h>
+#include <linux/gfp.h>
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/jiffies.h>
+#include <linux/hardirq.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/blk-io-throttle.h>
+
+#define ONE_SEC 1000000L /* # of microseconds in a second */
+#define KBS(x) ((x) * ONE_SEC >> 10)
+
+struct iothrottle_node {
+ struct list_head node;
+ dev_t dev;
+ unsigned long iorate;
+ unsigned long timestamp;
+ atomic_long_t stat;
+ long bucket_size;
+ atomic_long_t token;
+};
+
+struct iothrottle {
+ struct cgroup_subsys_state css;
+ /* protects the list below, not the single elements */
+ spinlock_t lock;
+ struct list_head list;
+ int strategy;
+};
+
+static inline struct iothrottle *cgroup_to_iothrottle(struct cgroup *cont)
+{
+ return container_of(cgroup_subsys_state(cont, iothrottle_subsys_id),
+ struct iothrottle, css);
+}
+
+static inline struct iothrottle *task_to_iothrottle(struct task_struct *task)
+{
+ return container_of(task_subsys_state(task, iothrottle_subsys_id),
+ struct iothrottle, css);
+}
+
+static inline struct iothrottle_node *iothrottle_search_node(
+ const struct iothrottle *iot,
+ dev_t dev)
+{
+ struct iothrottle_node *n;
+
+ list_for_each_entry_rcu(n, &iot->list, node)
+ if (n->dev == dev)
+ return n;
+ return NULL;
+}
+
+static inline void iothrottle_insert_node(struct iothrottle *iot,
+ struct iothrottle_node *n)
+{
+ list_add_rcu(&n->node, &iot->list);
+}
+
+static inline struct iothrottle_node *iothrottle_replace_node(
+ struct iothrottle *iot,
+ struct iothrottle_node *old,
+ struct iothrottle_node *new)
+{
+ list_replace_rcu(&old->node, &new->node);
+ return old;
+}
+
+static inline struct iothrottle_node *iothrottle_delete_node(
+ struct iothrottle *iot,
+ dev_t dev)
+{
+ struct iothrottle_node *n;
+
+ list_for_each_entry(n, &iot->list, node)
+ if (n->dev == dev) {
+ list_del_rcu(&n->node);
+ return n;
+ }
+ return NULL;
+}
+
+/*
+ * Note: called from kernel/cgroup.c with cgroup_lock() held.
+ */
+static struct cgroup_subsys_state *iothrottle_create(
+ struct cgroup_subsys *ss, struct cgroup *cont)
+{
+ struct iothrottle *iot;
+
+ iot = kmalloc(sizeof(*iot), GFP_KERNEL);
+ if (unlikely(!iot))
+ return ERR_PTR(-ENOMEM);
+
+ INIT_LIST_HEAD(&iot->list);
+ spin_lock_init(&iot->lock);
+ iot->strategy = 0;
+
+ return &iot->css;
+}
+
+/*
+ * Note: called from kernel/cgroup.c with cgroup_lock() held.
+ */
+static void iothrottle_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+ struct iothrottle_node *n, *p;
+ struct iothrottle *iot = cgroup_to_iothrottle(cont);
+
+ /*
+ * don't worry about locking here, at this point there must be not any
+ * reference to the list.
+ */
+ list_for_each_entry_safe(n, p, &iot->list, node)
+ kfree(n);
+ kfree(iot);
+}
+
+static ssize_t iothrottle_read(struct cgroup *cont,
+ struct cftype *cft,
+ struct file *file,
+ char __user *userbuf,
+ size_t nbytes,
+ loff_t *ppos)
+{
+ struct iothrottle *iot;
+ char *buffer;
+ int s = 0;
+ struct iothrottle_node *n;
+ ssize_t ret;
+
+ buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ iot = cgroup_to_iothrottle(cont);
+ rcu_read_lock();
+ list_for_each_entry_rcu(n, &iot->list, node) {
+ unsigned long delta, rate;
+
+ BUG_ON(!n->dev);
+ delta = jiffies_to_usecs((long)jiffies - (long)n->timestamp);
+ rate = delta ? KBS(atomic_long_read(&n->stat) / delta) : 0;
+ s += scnprintf(buffer + s, nbytes - s,
+ "device: %u,%u\n"
+ "bandwidth: %lu KiB/sec\n"
+ "usage: %lu KiB/sec\n"
+ "bucket size: %lu KiB\n"
+ "bucket fill: %li KiB\n",
+ MAJOR(n->dev), MINOR(n->dev),
+ n->iorate, rate,
+ n->bucket_size,
+ atomic_long_read(&n->token) >> 10);
+ }
+ rcu_read_unlock();
+ ret = simple_read_from_buffer(userbuf, nbytes, ppos, buffer, s);
+out:
+ cgroup_unlock();
+ kfree(buffer);
+ return ret;
+}
+
+static inline dev_t devname2dev_t(const char *buf)
+{
+ struct block_device *bdev;
+ dev_t ret;
+
+ bdev = lookup_bdev(buf);
+ if (IS_ERR(bdev))
+ return 0;
+
+ BUG_ON(!bdev->bd_inode);
+ ret = bdev->bd_inode->i_rdev;
+ bdput(bdev);
+
+ return ret;
+}
+
+static inline int iothrottle_parse_args(char *buf, size_t nbytes,
+ dev_t *dev, unsigned long *iorate,
+ unsigned long *bucket_size)
+{
+ char *ioratep, *bucket_sizep;
+
+ ioratep = memchr(buf, ':', nbytes);
+ if (!ioratep)
+ return -EINVAL;
+ *ioratep++ = '\0';
+
+ bucket_sizep = memchr(ioratep, ':', nbytes + ioratep - buf);
+ if (!bucket_sizep)
+ return -EINVAL;
+ *bucket_sizep++ = '\0';
+
+ /* i/o bandiwth is expressed in KiB/s */
+ *iorate = ALIGN(memparse(ioratep, &ioratep), 1024) >> 10;
+ if (*ioratep)
+ return -EINVAL;
+ *bucket_size = ALIGN(memparse(bucket_sizep, &bucket_sizep), 1024) >> 10;
+ if (*bucket_sizep)
+ return -EINVAL;
+
+ *dev = devname2dev_t(buf);
+ if (!*dev)
+ return -ENOTBLK;
+
+ return 0;
+}
+
+static ssize_t iothrottle_write(struct cgroup *cont,
+ struct cftype *cft,
+ struct file *file,
+ const char __user *userbuf,
+ size_t nbytes, loff_t *ppos)
+{
+ struct iothrottle *iot;
+ struct iothrottle_node *n, *tmpn = NULL;
+ char *buffer, *tmpp;
+ dev_t dev;
+ unsigned long iorate, bucket_size;
+ int ret;
+
+ if (!nbytes)
+ return -EINVAL;
+
+ /* Upper limit on largest io-throttle rule string user might write. */
+ if (nbytes > 1024)
+ return -E2BIG;
+
+ buffer = kmalloc(nbytes + 1, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+
+ if (copy_from_user(buffer, userbuf, nbytes)) {
+ ret = -EFAULT;
+ goto out1;
+ }
+
+ buffer[nbytes] = '\0';
+ tmpp = strstrip(buffer);
+
+ ret = iothrottle_parse_args(tmpp, nbytes, &dev, &iorate, &bucket_size);
+ if (ret)
+ goto out1;
+
+ if (iorate) {
+ tmpn = kmalloc(sizeof(*tmpn), GFP_KERNEL);
+ if (!tmpn) {
+ ret = -ENOMEM;
+ goto out1;
+ }
+ atomic_long_set(&tmpn->stat, 0);
+ tmpn->timestamp = jiffies;
+ tmpn->iorate = iorate;
+ tmpn->bucket_size = bucket_size;
+ atomic_long_set(&tmpn->token, 0);
+ tmpn->dev = dev;
+ }
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ ret = -ENODEV;
+ goto out2;
+ }
+
+ iot = cgroup_to_iothrottle(cont);
+ spin_lock(&iot->lock);
+ if (!iorate) {
+ /* Delete a block device limiting rule */
+ n = iothrottle_delete_node(iot, dev);
+ goto out3;
+ }
+ n = iothrottle_search_node(iot, dev);
+ if (n) {
+ /* Update a block device limiting rule */
+ iothrottle_replace_node(iot, n, tmpn);
+ goto out3;
+ }
+ /* Add a new block device limiting rule */
+ iothrottle_insert_node(iot, tmpn);
+out3:
+ ret = nbytes;
+ spin_unlock(&iot->lock);
+ if (n) {
+ synchronize_rcu();
+ kfree(n);
+ }
+out2:
+ cgroup_unlock();
+out1:
+ kfree(buffer);
+ return ret;
+}
+
+static s64 iothrottle_strategy_read(struct cgroup *cont, struct cftype *cft)
+{
+ struct iothrottle *iot;
+ s64 ret;
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ cgroup_unlock();
+ return -ENODEV;
+ }
+ iot = cgroup_to_iothrottle(cont);
+ ret = iot->strategy;
+ cgroup_unlock();
+ return ret;
+}
+
+static int iothrottle_strategy_write(struct cgroup *cont,
+ struct cftype *cft, s64 val)
+{
+ struct iothrottle *iot;
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ cgroup_unlock();
+ return -ENODEV;
+ }
+ iot = cgroup_to_iothrottle(cont);
+ iot->strategy = (int)val;
+ cgroup_unlock();
+ return 0;
+}
+
+static struct cftype files[] = {
+ {
+ .name = "bandwidth",
+ .read = iothrottle_read,
+ .write = iothrottle_write,
+ },
+ {
+ .name = "throttling_strategy",
+ .read_s64 = iothrottle_strategy_read,
+ .write_s64 = iothrottle_strategy_write,
+ },
+};
+
+static int iothrottle_populate(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+ return cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
+}
+
+struct cgroup_subsys iothrottle_subsys = {
+ .name = "blockio",
+ .create = iothrottle_create,
+ .destroy = iothrottle_destroy,
+ .populate = iothrottle_populate,
+ .subsys_id = iothrottle_subsys_id,
+};
+
+static inline int __cant_sleep(void)
+{
+ return in_atomic() || in_interrupt() || irqs_disabled();
+}
+
+static long leaky_bucket(struct iothrottle_node *n, size_t bytes)
+{
+ unsigned long delta, t;
+ long sleep;
+
+ /* Account the i/o activity */
+ atomic_long_add(bytes, &n->stat);
+
+ /* Evaluate if we need to throttle the current process */
+ delta = (long)jiffies - (long)n->timestamp;
+ if (!delta)
+ return 0;
+
+ t = usecs_to_jiffies(KBS(atomic_long_read(&n->stat) / n->iorate));
+ if (!t)
+ return 0;
+
+ sleep = t - delta;
+ if (unlikely(sleep > 0))
+ return sleep;
+
+ /* Reset i/o statistics */
+ atomic_long_set(&n->stat, 0);
+ /*
+ * NOTE: be sure i/o statistics have been resetted before updating the
+ * timestamp, otherwise a very small time delta may possibly be read by
+ * another CPU w.r.t. accounted i/o statistics, generating unnecessary
+ * long sleeps.
+ */
+ smp_wmb();
+ n->timestamp = jiffies;
+ return 0;
+}
+
+/* XXX: need locking in order to evaluate a consistent sleep??? */
+static long token_bucket(struct iothrottle_node *n, size_t bytes)
+{
+ unsigned long delta;
+ long tok;
+
+ atomic_long_sub(bytes, &n->token);
+
+ delta = (long)jiffies - (long)n->timestamp;
+ if (!delta)
+ return 0;
+
+ n->timestamp = jiffies;
+ tok = atomic_long_read(&n->token) + jiffies_to_msecs(delta) * n->iorate;
+ if (tok > n->bucket_size)
+ tok = n->bucket_size;
+ atomic_long_set(&n->token, tok);
+
+ return (tok < 0) ? msecs_to_jiffies(-tok / n->iorate) : 0;
+}
+
+void cgroup_io_throttle(struct block_device *bdev, size_t bytes)
+{
+ struct iothrottle *iot;
+ struct iothrottle_node *n;
+ long sleep;
+
+ if (unlikely(!bdev || !bytes))
+ return;
+
+ iot = task_to_iothrottle(current);
+ if (unlikely(!iot))
+ return;
+
+ BUG_ON(!bdev->bd_inode);
+
+ rcu_read_lock();
+ n = iothrottle_search_node(iot, bdev->bd_inode->i_rdev);
+ if (!n || !n->iorate) {
+ rcu_read_unlock();
+ return;
+ }
+ switch (iot->strategy) {
+ case 0:
+ sleep = leaky_bucket(n, bytes);
+ break;
+ case 1:
+ sleep = token_bucket(n, bytes);
+ break;
+ default:
+ sleep = 0;
+ }
+ if (unlikely(sleep)) {
+ rcu_read_unlock();
+ if (__cant_sleep())
+ return;
+ pr_debug("io-throttle: task %p (%s) must sleep %lu jiffies\n",
+ current, current->comm, sleep);
+ schedule_timeout_killable(sleep);
+ return;
+ }
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(cgroup_io_throttle);
diff --git a/include/linux/blk-io-throttle.h b/include/linux/blk-io-throttle.h
new file mode 100644
index 0000000..3e08738
--- /dev/null
+++ b/include/linux/blk-io-throttle.h
@@ -0,0 +1,12 @@
+#ifndef BLK_IO_THROTTLE_H
+#define BLK_IO_THROTTLE_H
+
+#ifdef CONFIG_CGROUP_IO_THROTTLE
+extern void cgroup_io_throttle(struct block_device *bdev, size_t bytes);
+#else
+static inline void cgroup_io_throttle(struct block_device *bdev, size_t bytes)
+{
+}
+#endif /* CONFIG_CGROUP_IO_THROTTLE */
+
+#endif /* BLK_IO_THROTTLE_H */
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index e287745..0caf3c2 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -48,3 +48,9 @@ SUBSYS(devices)
#endif

/* */
+
+#ifdef CONFIG_CGROUP_IO_THROTTLE
+SUBSYS(iothrottle)
+#endif
+
+/* */
diff --git a/init/Kconfig b/init/Kconfig
index 6199d11..3117d99 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -306,6 +306,16 @@ config CGROUP_DEVICE
Provides a cgroup implementing whitelists for devices which
a process in the cgroup can mknod or open.

+config CGROUP_IO_THROTTLE
+ bool "Enable cgroup I/O throttling (EXPERIMENTAL)"
+ depends on CGROUPS && EXPERIMENTAL
+ help
+ This allows to limit the maximum I/O bandwidth for specific
+ cgroup(s).
+ See Documentation/controllers/io-throttle.txt for more information.
+
+ If unsure, say N.
+
config CPUSETS
bool "Cpuset support"
depends on SMP && CGROUPS

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