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Message-ID: <20090420175904.GD6822@linux.vnet.ibm.com>
Date: Mon, 20 Apr 2009 10:59:04 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Andrea Righi <righi.andrea@...il.com>
Cc: Paul Menage <menage@...gle.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Gui Jianfeng <guijianfeng@...fujitsu.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
agk@...rceware.org, akpm@...ux-foundation.org, axboe@...nel.dk,
baramsori72@...il.com, Carl Henrik Lunde <chlunde@...g.uio.no>,
dave@...ux.vnet.ibm.com, Divyesh Shah <dpshah@...gle.com>,
eric.rannaud@...il.com, fernando@....ntt.co.jp,
Hirokazu Takahashi <taka@...inux.co.jp>,
Li Zefan <lizf@...fujitsu.com>, matt@...ehost.com,
dradford@...ehost.com, ngupta@...gle.com, randy.dunlap@...cle.com,
roberto@...it.it, Ryo Tsuruta <ryov@...inux.co.jp>,
Satoshi UCHIDA <s-uchida@...jp.nec.com>,
subrata@...ux.vnet.ibm.com, yoshikawa.takuya@....ntt.co.jp,
Nauman Rafique <nauman@...gle.com>, fchecconi@...il.com,
paolo.valente@...more.it, containers@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] io-throttle controller infrastructure
On Sat, Apr 18, 2009 at 11:38:29PM +0200, Andrea Righi wrote:
> This is the core of the io-throttle kernel infrastructure. It creates
> the basic interfaces to the cgroup subsystem and implements the I/O
> measurement and throttling functionality.
A few questions interspersed below.
Thanx, Paul
> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
> Signed-off-by: Andrea Righi <righi.andrea@...il.com>
> ---
> block/Makefile | 1 +
> block/blk-io-throttle.c | 822 +++++++++++++++++++++++++++++++++++++++
> include/linux/blk-io-throttle.h | 144 +++++++
> include/linux/cgroup_subsys.h | 6 +
> init/Kconfig | 12 +
> 5 files changed, 985 insertions(+), 0 deletions(-)
> create mode 100644 block/blk-io-throttle.c
> create mode 100644 include/linux/blk-io-throttle.h
>
> diff --git a/block/Makefile b/block/Makefile
> index e9fa4dd..42b6a46 100644
> --- a/block/Makefile
> +++ b/block/Makefile
> @@ -13,5 +13,6 @@ obj-$(CONFIG_IOSCHED_AS) += as-iosched.o
> obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
> obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
>
> +obj-$(CONFIG_CGROUP_IO_THROTTLE) += blk-io-throttle.o
> obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
> obj-$(CONFIG_BLK_DEV_INTEGRITY) += blk-integrity.o
> diff --git a/block/blk-io-throttle.c b/block/blk-io-throttle.c
> new file mode 100644
> index 0000000..c8214fc
> --- /dev/null
> +++ b/block/blk-io-throttle.c
> @@ -0,0 +1,822 @@
> +/*
> + * 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@...il.com>
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/res_counter.h>
> +#include <linux/memcontrol.h>
> +#include <linux/slab.h>
> +#include <linux/gfp.h>
> +#include <linux/err.h>
> +#include <linux/genhd.h>
> +#include <linux/hardirq.h>
> +#include <linux/list.h>
> +#include <linux/seq_file.h>
> +#include <linux/spinlock.h>
> +#include <linux/blk-io-throttle.h>
> +#include <linux/mm.h>
> +#include <linux/page_cgroup.h>
> +#include <linux/sched.h>
> +#include <linux/bio.h>
> +
> +/*
> + * Statistics for I/O bandwidth controller.
> + */
> +enum iothrottle_stat_index {
> + /* # of times the cgroup has been throttled for bw limit */
> + IOTHROTTLE_STAT_BW_COUNT,
> + /* # of jiffies spent to sleep for throttling for bw limit */
> + IOTHROTTLE_STAT_BW_SLEEP,
> + /* # of times the cgroup has been throttled for iops limit */
> + IOTHROTTLE_STAT_IOPS_COUNT,
> + /* # of jiffies spent to sleep for throttling for iops limit */
> + IOTHROTTLE_STAT_IOPS_SLEEP,
> + /* total number of bytes read and written */
> + IOTHROTTLE_STAT_BYTES_TOT,
> + /* total number of I/O operations */
> + IOTHROTTLE_STAT_IOPS_TOT,
> +
> + IOTHROTTLE_STAT_NSTATS,
> +};
> +
> +struct iothrottle_stat_cpu {
> + unsigned long long count[IOTHROTTLE_STAT_NSTATS];
> +} ____cacheline_aligned_in_smp;
> +
> +struct iothrottle_stat {
> + struct iothrottle_stat_cpu cpustat[NR_CPUS];
> +};
> +
> +static void iothrottle_stat_add(struct iothrottle_stat *stat,
> + enum iothrottle_stat_index type, unsigned long long val)
> +{
> + int cpu = get_cpu();
> +
> + stat->cpustat[cpu].count[type] += val;
> + put_cpu();
> +}
> +
> +static void iothrottle_stat_add_sleep(struct iothrottle_stat *stat,
> + int type, unsigned long long sleep)
> +{
> + int cpu = get_cpu();
> +
> + switch (type) {
> + case IOTHROTTLE_BANDWIDTH:
> + stat->cpustat[cpu].count[IOTHROTTLE_STAT_BW_COUNT]++;
> + stat->cpustat[cpu].count[IOTHROTTLE_STAT_BW_SLEEP] += sleep;
> + break;
> + case IOTHROTTLE_IOPS:
> + stat->cpustat[cpu].count[IOTHROTTLE_STAT_IOPS_COUNT]++;
> + stat->cpustat[cpu].count[IOTHROTTLE_STAT_IOPS_SLEEP] += sleep;
> + break;
> + }
> + put_cpu();
> +}
> +
> +static unsigned long long iothrottle_read_stat(struct iothrottle_stat *stat,
> + enum iothrottle_stat_index idx)
> +{
> + int cpu;
> + unsigned long long ret = 0;
> +
> + for_each_possible_cpu(cpu)
> + ret += stat->cpustat[cpu].count[idx];
> + return ret;
> +}
> +
> +struct iothrottle_sleep {
> + unsigned long long bw_sleep;
> + unsigned long long iops_sleep;
> +};
> +
> +/*
> + * struct iothrottle_node - throttling rule of a single block device
> + * @node: list of per block device throttling rules
> + * @dev: block device number, used as key in the list
> + * @bw: max i/o bandwidth (in bytes/s)
> + * @iops: max i/o operations per second
> + * @stat: throttling statistics
> + *
> + * Define a i/o throttling rule for a single block device.
> + *
> + * NOTE: limiting rules always refer to dev_t; if a block device is unplugged
> + * the limiting rules defined for that device persist and they are still valid
> + * if a new device is plugged and it uses the same dev_t number.
> + */
> +struct iothrottle_node {
> + struct list_head node;
> + dev_t dev;
> + struct res_counter bw;
> + struct res_counter iops;
> + struct iothrottle_stat stat;
> +};
> +
> +/**
> + * struct iothrottle - throttling rules for a cgroup
> + * @css: pointer to the cgroup state
> + * @list: list of iothrottle_node elements
> + *
> + * Define multiple per-block device i/o throttling rules.
> + * Note: the list of the throttling rules is protected by RCU locking:
> + * - hold cgroup_lock() for update.
> + * - hold rcu_read_lock() for read.
> + */
> +struct iothrottle {
> + struct cgroup_subsys_state css;
> + struct list_head list;
> +};
> +static struct iothrottle init_iothrottle;
> +
> +static inline struct iothrottle *cgroup_to_iothrottle(struct cgroup *cgrp)
> +{
> + return container_of(cgroup_subsys_state(cgrp, iothrottle_subsys_id),
> + struct iothrottle, css);
> +}
> +
> +/*
> + * Note: called with rcu_read_lock() held.
> + */
> +static inline struct iothrottle *task_to_iothrottle(struct task_struct *task)
> +{
> + return container_of(task_subsys_state(task, iothrottle_subsys_id),
> + struct iothrottle, css);
OK, task_subsys_state() has an rcu_dereference(), so...
> +}
> +
> +/*
> + * Note: called with rcu_read_lock() or iot->lock held.
> + */
> +static struct iothrottle_node *
> +iothrottle_search_node(const struct iothrottle *iot, dev_t dev)
> +{
> + struct iothrottle_node *n;
> +
> + if (list_empty(&iot->list))
> + return NULL;
> + list_for_each_entry_rcu(n, &iot->list, node)
> + if (n->dev == dev)
> + return n;
> + return NULL;
> +}
> +
> +/*
> + * Note: called with iot->lock held.
Should this be a WARN_ON() or something similar? The machine is unable
to enforce a comment. ;-)
> + */
> +static inline void iothrottle_insert_node(struct iothrottle *iot,
> + struct iothrottle_node *n)
> +{
> + list_add_rcu(&n->node, &iot->list);
> +}
> +
> +/*
> + * Note: called with iot->lock held.
Ditto.
> + */
> +static inline void
> +iothrottle_replace_node(struct iothrottle *iot, struct iothrottle_node *old,
> + struct iothrottle_node *new)
> +{
> + list_replace_rcu(&old->node, &new->node);
> +}
> +
> +/*
> + * Note: called with iot->lock held.
Ditto.
> + */
> +static inline void
> +iothrottle_delete_node(struct iothrottle *iot, struct iothrottle_node *n)
> +{
> + list_del_rcu(&n->node);
> +}
> +
> +/*
> + * Note: called from kernel/cgroup.c with cgroup_lock() held.
> + */
> +static struct cgroup_subsys_state *
> +iothrottle_create(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +{
> + struct iothrottle *iot;
> +
> + if (unlikely((cgrp->parent) == NULL)) {
> + iot = &init_iothrottle;
> + } else {
> + iot = kzalloc(sizeof(*iot), GFP_KERNEL);
> + if (unlikely(!iot))
> + return ERR_PTR(-ENOMEM);
> + }
> + INIT_LIST_HEAD(&iot->list);
> +
> + return &iot->css;
> +}
> +
> +/*
> + * Note: called from kernel/cgroup.c with cgroup_lock() held.
> + */
> +static void iothrottle_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +{
> + struct iothrottle_node *n, *p;
> + struct iothrottle *iot = cgroup_to_iothrottle(cgrp);
> +
> + free_css_id(&iothrottle_subsys, &iot->css);
> + /*
> + * don't worry about locking here, at this point there must be not any
> + * reference to the list.
> + */
> + if (!list_empty(&iot->list))
> + list_for_each_entry_safe(n, p, &iot->list, node)
> + kfree(n);
> + kfree(iot);
> +}
> +
> +/*
> + * NOTE: called with rcu_read_lock() held.
> + *
> + * do not care too much about locking for single res_counter values here.
> + */
> +static void iothrottle_show_limit(struct seq_file *m, dev_t dev,
> + struct res_counter *res)
> +{
> + if (!res->limit)
> + return;
> + seq_printf(m, "%u %u %llu %llu %lli %llu %li\n",
> + MAJOR(dev), MINOR(dev),
> + res->limit, res->policy,
> + (long long)res->usage, res->capacity,
> + jiffies_to_clock_t(res_counter_ratelimit_delta_t(res)));
OK, looks like the rcu_dereference() in the list_for_each_entry_rcu() in
the caller suffices here. But thought I should ask the question anyway,
even though at first glance it does look correct.
> +}
> +
> +/*
> + * NOTE: called with rcu_read_lock() held.
> + *
> + */
> +static void iothrottle_show_failcnt(struct seq_file *m, dev_t dev,
> + struct iothrottle_stat *stat)
> +{
> + unsigned long long bw_count, bw_sleep, iops_count, iops_sleep;
> +
> + bw_count = iothrottle_read_stat(stat, IOTHROTTLE_STAT_BW_COUNT);
> + bw_sleep = iothrottle_read_stat(stat, IOTHROTTLE_STAT_BW_SLEEP);
> + iops_count = iothrottle_read_stat(stat, IOTHROTTLE_STAT_IOPS_COUNT);
> + iops_sleep = iothrottle_read_stat(stat, IOTHROTTLE_STAT_IOPS_SLEEP);
> +
> + seq_printf(m, "%u %u %llu %li %llu %li\n", MAJOR(dev), MINOR(dev),
> + bw_count, jiffies_to_clock_t(bw_sleep),
> + iops_count, jiffies_to_clock_t(iops_sleep));
Ditto.
> +}
> +
> +/*
> + * NOTE: called with rcu_read_lock() held.
> + */
> +static void iothrottle_show_stat(struct seq_file *m, dev_t dev,
> + struct iothrottle_stat *stat)
> +{
> + unsigned long long bytes, iops;
> +
> + bytes = iothrottle_read_stat(stat, IOTHROTTLE_STAT_BYTES_TOT);
> + iops = iothrottle_read_stat(stat, IOTHROTTLE_STAT_IOPS_TOT);
> +
> + seq_printf(m, "%u %u %llu %llu\n", MAJOR(dev), MINOR(dev), bytes, iops);
Ditto.
> +}
> +
> +static int iothrottle_read(struct cgroup *cgrp, struct cftype *cft,
> + struct seq_file *m)
> +{
> + struct iothrottle *iot = cgroup_to_iothrottle(cgrp);
> + struct iothrottle_node *n;
> +
> + rcu_read_lock();
> + if (list_empty(&iot->list))
> + goto unlock_and_return;
> + list_for_each_entry_rcu(n, &iot->list, node) {
> + BUG_ON(!n->dev);
> + switch (cft->private) {
> + case IOTHROTTLE_BANDWIDTH:
> + iothrottle_show_limit(m, n->dev, &n->bw);
> + break;
> + case IOTHROTTLE_IOPS:
> + iothrottle_show_limit(m, n->dev, &n->iops);
> + break;
> + case IOTHROTTLE_FAILCNT:
> + iothrottle_show_failcnt(m, n->dev, &n->stat);
> + break;
> + case IOTHROTTLE_STAT:
> + iothrottle_show_stat(m, n->dev, &n->stat);
> + break;
> + }
> + }
> +unlock_and_return:
> + rcu_read_unlock();
> + return 0;
> +}
> +
> +static dev_t devname2dev_t(const char *buf)
> +{
> + struct block_device *bdev;
> + dev_t dev = 0;
> + struct gendisk *disk;
> + int part;
> +
> + /* use a lookup to validate the block device */
> + bdev = lookup_bdev(buf);
> + if (IS_ERR(bdev))
> + return 0;
> + /* only entire devices are allowed, not single partitions */
> + disk = get_gendisk(bdev->bd_dev, &part);
> + if (disk && !part) {
> + BUG_ON(!bdev->bd_inode);
> + dev = bdev->bd_inode->i_rdev;
> + }
> + bdput(bdev);
> +
> + return dev;
> +}
> +
> +/*
> + * The userspace input string must use one of the following syntaxes:
> + *
> + * dev:0 <- delete an i/o limiting rule
> + * dev:io-limit:0 <- set a leaky bucket throttling rule
> + * dev:io-limit:1:bucket-size <- set a token bucket throttling rule
> + * dev:io-limit:1 <- set a token bucket throttling rule using
> + * bucket-size == io-limit
> + */
> +static int iothrottle_parse_args(char *buf, size_t nbytes, int filetype,
> + dev_t *dev, unsigned long long *iolimit,
> + unsigned long long *strategy,
> + unsigned long long *bucket_size)
> +{
> + char *p;
> + int count = 0;
> + char *s[4];
> + int ret;
> +
> + memset(s, 0, sizeof(s));
> + *dev = 0;
> + *iolimit = 0;
> + *strategy = 0;
> + *bucket_size = 0;
> +
> + /* split the colon-delimited input string into its elements */
> + while (count < ARRAY_SIZE(s)) {
> + p = strsep(&buf, ":");
> + if (!p)
> + break;
> + if (!*p)
> + continue;
> + s[count++] = p;
> + }
> +
> + /* i/o limit */
> + if (!s[1])
> + return -EINVAL;
> + ret = strict_strtoull(s[1], 10, iolimit);
> + if (ret < 0)
> + return ret;
> + if (!*iolimit)
> + goto out;
> + /* throttling strategy (leaky bucket / token bucket) */
> + if (!s[2])
> + return -EINVAL;
> + ret = strict_strtoull(s[2], 10, strategy);
> + if (ret < 0)
> + return ret;
> + switch (*strategy) {
> + case RATELIMIT_LEAKY_BUCKET:
> + goto out;
> + case RATELIMIT_TOKEN_BUCKET:
> + break;
> + default:
> + return -EINVAL;
> + }
> + /* bucket size */
> + if (!s[3])
> + *bucket_size = *iolimit;
> + else {
> + ret = strict_strtoll(s[3], 10, bucket_size);
> + if (ret < 0)
> + return ret;
> + }
> + if (*bucket_size <= 0)
> + return -EINVAL;
> +out:
> + /* block device number */
> + *dev = devname2dev_t(s[0]);
> + return *dev ? 0 : -EINVAL;
> +}
> +
> +static int iothrottle_write(struct cgroup *cgrp, struct cftype *cft,
> + const char *buffer)
> +{
> + struct iothrottle *iot;
> + struct iothrottle_node *n, *newn = NULL;
> + dev_t dev;
> + unsigned long long iolimit, strategy, bucket_size;
> + char *buf;
> + size_t nbytes = strlen(buffer);
> + int ret = 0;
> +
> + /*
> + * We need to allocate a new buffer here, because
> + * iothrottle_parse_args() can modify it and the buffer provided by
> + * write_string is supposed to be const.
> + */
> + buf = kmalloc(nbytes + 1, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> + memcpy(buf, buffer, nbytes + 1);
> +
> + ret = iothrottle_parse_args(buf, nbytes, cft->private, &dev, &iolimit,
> + &strategy, &bucket_size);
> + if (ret)
> + goto out1;
> + newn = kzalloc(sizeof(*newn), GFP_KERNEL);
> + if (!newn) {
> + ret = -ENOMEM;
> + goto out1;
> + }
> + newn->dev = dev;
> + res_counter_init(&newn->bw, NULL);
> + res_counter_init(&newn->iops, NULL);
> +
> + switch (cft->private) {
> + case IOTHROTTLE_BANDWIDTH:
> + res_counter_ratelimit_set_limit(&newn->iops, 0, 0, 0);
> + res_counter_ratelimit_set_limit(&newn->bw, strategy,
> + ALIGN(iolimit, 1024), ALIGN(bucket_size, 1024));
> + break;
> + case IOTHROTTLE_IOPS:
> + res_counter_ratelimit_set_limit(&newn->bw, 0, 0, 0);
> + /*
> + * scale up iops cost by a factor of 1000, this allows to apply
> + * a more fine grained sleeps, and throttling results more
> + * precise this way.
> + */
> + res_counter_ratelimit_set_limit(&newn->iops, strategy,
> + iolimit * 1000, bucket_size * 1000);
> + break;
> + default:
> + WARN_ON(1);
> + break;
> + }
> +
> + if (!cgroup_lock_live_group(cgrp)) {
> + ret = -ENODEV;
> + goto out1;
> + }
> + iot = cgroup_to_iothrottle(cgrp);
> +
> + n = iothrottle_search_node(iot, dev);
> + if (!n) {
> + if (iolimit) {
> + /* Add a new block device limiting rule */
> + iothrottle_insert_node(iot, newn);
> + newn = NULL;
> + }
> + goto out2;
> + }
> + switch (cft->private) {
> + case IOTHROTTLE_BANDWIDTH:
> + if (!iolimit && !n->iops.limit) {
> + /* Delete a block device limiting rule */
> + iothrottle_delete_node(iot, n);
> + goto out2;
> + }
> + if (!n->iops.limit)
> + break;
> + /* Update a block device limiting rule */
> + newn->iops = n->iops;
> + break;
> + case IOTHROTTLE_IOPS:
> + if (!iolimit && !n->bw.limit) {
> + /* Delete a block device limiting rule */
> + iothrottle_delete_node(iot, n);
> + goto out2;
> + }
> + if (!n->bw.limit)
> + break;
> + /* Update a block device limiting rule */
> + newn->bw = n->bw;
> + break;
> + }
> + iothrottle_replace_node(iot, n, newn);
> + newn = NULL;
> +out2:
> + cgroup_unlock();
How does the above lock relate to the iot->lock called out in the comment
headers in the earlier functions? Hmmm... Come to think of it, I don't
see an acquisition of iot->lock anywhere.
So, what is the story here?
> + if (n) {
> + synchronize_rcu();
> + kfree(n);
> + }
> +out1:
> + kfree(newn);
> + kfree(buf);
> + return ret;
> +}
> +
> +static struct cftype files[] = {
> + {
> + .name = "bandwidth-max",
> + .read_seq_string = iothrottle_read,
> + .write_string = iothrottle_write,
> + .max_write_len = 256,
> + .private = IOTHROTTLE_BANDWIDTH,
> + },
> + {
> + .name = "iops-max",
> + .read_seq_string = iothrottle_read,
> + .write_string = iothrottle_write,
> + .max_write_len = 256,
> + .private = IOTHROTTLE_IOPS,
> + },
> + {
> + .name = "throttlecnt",
> + .read_seq_string = iothrottle_read,
> + .private = IOTHROTTLE_FAILCNT,
> + },
> + {
> + .name = "stat",
> + .read_seq_string = iothrottle_read,
> + .private = IOTHROTTLE_STAT,
> + },
> +};
> +
> +static int iothrottle_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +{
> + return cgroup_add_files(cgrp, 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,
> + .early_init = 1,
> + .use_id = 1,
> +};
> +
> +/*
> + * NOTE: called with rcu_read_lock() held.
> + */
> +static void iothrottle_evaluate_sleep(struct iothrottle_sleep *sleep,
> + struct iothrottle *iot,
> + struct block_device *bdev, ssize_t bytes)
> +{
> + struct iothrottle_node *n;
> + dev_t dev;
> +
> + BUG_ON(!iot);
> +
> + /* accounting and throttling is done only on entire block devices */
> + dev = MKDEV(MAJOR(bdev->bd_inode->i_rdev), bdev->bd_disk->first_minor);
> + n = iothrottle_search_node(iot, dev);
> + if (!n)
> + return;
> +
> + /* Update statistics */
> + iothrottle_stat_add(&n->stat, IOTHROTTLE_STAT_BYTES_TOT, bytes);
> + if (bytes)
> + iothrottle_stat_add(&n->stat, IOTHROTTLE_STAT_IOPS_TOT, 1);
> +
> + /* Evaluate sleep values */
> + sleep->bw_sleep = res_counter_ratelimit_sleep(&n->bw, bytes);
> + /*
> + * scale up iops cost by a factor of 1000, this allows to apply
> + * a more fine grained sleeps, and throttling works better in
> + * this way.
> + *
> + * Note: do not account any i/o operation if bytes is negative or zero.
> + */
> + sleep->iops_sleep = res_counter_ratelimit_sleep(&n->iops,
> + bytes ? 1000 : 0);
> +}
> +
> +/*
> + * NOTE: called with rcu_read_lock() held.
> + */
> +static void iothrottle_acct_stat(struct iothrottle *iot,
> + struct block_device *bdev, int type,
> + unsigned long long sleep)
> +{
> + struct iothrottle_node *n;
> + dev_t dev = MKDEV(MAJOR(bdev->bd_inode->i_rdev),
> + bdev->bd_disk->first_minor);
> +
> + n = iothrottle_search_node(iot, dev);
> + if (!n)
> + return;
> + iothrottle_stat_add_sleep(&n->stat, type, sleep);
> +}
> +
> +static void iothrottle_acct_task_stat(int type, unsigned long long sleep)
> +{
> + /*
> + * XXX: per-task statistics may be inaccurate (this is not a
> + * critical issue, anyway, respect to introduce locking
> + * overhead or increase the size of task_struct).
> + */
> + switch (type) {
> + case IOTHROTTLE_BANDWIDTH:
> + current->io_throttle_bw_cnt++;
> + current->io_throttle_bw_sleep += sleep;
> + break;
> +
> + case IOTHROTTLE_IOPS:
> + current->io_throttle_iops_cnt++;
> + current->io_throttle_iops_sleep += sleep;
> + break;
> + }
> +}
> +
> +/*
> + * A helper function to get iothrottle from css id.
> + *
> + * NOTE: must be called under rcu_read_lock(). The caller must check
> + * css_is_removed() or some if it's concern.
> + */
> +static struct iothrottle *iothrottle_lookup(unsigned long id)
> +{
> + struct cgroup_subsys_state *css;
> +
> + if (!id)
> + return NULL;
> + css = css_lookup(&iothrottle_subsys, id);
> + if (!css)
> + return NULL;
> + return container_of(css, struct iothrottle, css);
> +}
> +
> +static struct iothrottle *get_iothrottle_from_page(struct page *page)
> +{
> + struct iothrottle *iot;
> + unsigned long id;
> +
> + BUG_ON(!page);
> + id = page_cgroup_get_owner(page);
> +
> + rcu_read_lock();
> + iot = iothrottle_lookup(id);
> + if (!iot)
> + goto out;
> + css_get(&iot->css);
> +out:
> + rcu_read_unlock();
> + return iot;
> +}
> +
> +static struct iothrottle *get_iothrottle_from_bio(struct bio *bio)
> +{
> + if (!bio)
> + return NULL;
> + return get_iothrottle_from_page(bio_page(bio));
> +}
> +
> +int iothrottle_set_page_owner(struct page *page, struct mm_struct *mm)
> +{
> + struct iothrottle *iot;
> + unsigned short id = 0;
> +
> + if (iothrottle_disabled())
> + return 0;
> + if (!mm)
> + goto out;
> + rcu_read_lock();
> + iot = task_to_iothrottle(rcu_dereference(mm->owner));
Given that task_to_iothrottle() calls task_subsys_state(), which contains
an rcu_dereference(), why is the rcu_dereference() above required?
(There might well be a good reason, just cannot see it right offhand.)
> + if (likely(iot))
> + id = css_id(&iot->css);
> + rcu_read_unlock();
> +out:
> + return page_cgroup_set_owner(page, id);
> +}
> +
> +int iothrottle_set_pagedirty_owner(struct page *page, struct mm_struct *mm)
> +{
> + if (PageSwapCache(page) || PageAnon(page))
> + return 0;
> + if (current->flags & PF_MEMALLOC)
> + return 0;
> + return iothrottle_set_page_owner(page, mm);
> +}
> +
> +int iothrottle_copy_page_owner(struct page *npage, struct page *opage)
> +{
> + if (iothrottle_disabled())
> + return 0;
> + return page_cgroup_copy_owner(npage, opage);
> +}
> +
> +static inline int is_kthread_io(void)
> +{
> + return current->flags & (PF_KTHREAD | PF_FLUSHER | PF_KSWAPD);
> +}
> +
> +static inline bool is_urgent_io(struct bio *bio)
> +{
> + if (bio && (bio_rw_meta(bio) || bio_noidle(bio)))
> + return true;
> + if (has_fs_excl())
> + return true;
> + return false;
> +}
> +
> +/**
> + * cgroup_io_throttle() - account and throttle synchronous i/o activity
> + * @bio: the bio structure used to retrieve the owner of the i/o
> + * operation.
> + * @bdev: block device involved for the i/o.
> + * @bytes: size in bytes of the i/o operation.
> + *
> + * This is the core of the block device i/o bandwidth controller. This function
> + * must be called by any function that generates i/o activity (directly or
> + * indirectly). It provides both i/o accounting and throttling functionalities;
> + * throttling is disabled if @can_sleep is set to 0.
> + *
> + * Returns the value of sleep in jiffies if it was not possible to schedule the
> + * timeout.
> + **/
> +unsigned long long
> +cgroup_io_throttle(struct bio *bio, struct block_device *bdev, ssize_t bytes)
> +{
> + struct iothrottle *iot = NULL;
> + struct iothrottle_sleep s = {};
> + unsigned long long sleep;
> + int can_sleep = 1;
> +
> + if (iothrottle_disabled())
> + return 0;
> + if (unlikely(!bdev))
> + return 0;
> + BUG_ON(!bdev->bd_inode || !bdev->bd_disk);
> + /*
> + * Never throttle kernel threads directly, since they may completely
> + * block other cgroups, the i/o on other block devices or even the
> + * whole system.
> + *
> + * For the same reason never throttle IO that comes from tasks that are
> + * holding exclusive access resources (urgent IO).
> + *
> + * And never sleep if we're inside an AIO context; just account the i/o
> + * activity. Throttling is performed in io_submit_one() returning
> + * -EAGAIN when the limits are exceeded.
> + */
> + if (is_kthread_io() || is_urgent_io(bio) || is_in_aio())
> + can_sleep = 0;
> + /*
> + * WARNING: in_atomic() do not know about held spinlocks in
> + * non-preemptible kernels, but we want to check it here to raise
> + * potential bugs when a preemptible kernel is used.
> + */
> + WARN_ON_ONCE(can_sleep &&
> + (irqs_disabled() || in_interrupt() || in_atomic()));
> +
> + /* Apply IO throttling */
> + iot = get_iothrottle_from_bio(bio);
> + rcu_read_lock();
> + if (!iot) {
> + /* IO occurs in the same context of the current task */
> + iot = task_to_iothrottle(current);
> + css_get(&iot->css);
> + }
> + iothrottle_evaluate_sleep(&s, iot, bdev, bytes);
> + sleep = max(s.bw_sleep, s.iops_sleep);
> + if (unlikely(sleep && can_sleep)) {
> + int type = (s.bw_sleep < s.iops_sleep) ?
> + IOTHROTTLE_IOPS : IOTHROTTLE_BANDWIDTH;
> +
> + iothrottle_acct_stat(iot, bdev, type, sleep);
> + css_put(&iot->css);
> + rcu_read_unlock();
> +
> + pr_debug("io-throttle: task %p (%s) must sleep %llu jiffies\n",
> + current, current->comm, sleep);
> + iothrottle_acct_task_stat(type, sleep);
> + schedule_timeout_killable(sleep);
> + return 0;
> + }
> + css_put(&iot->css);
> + rcu_read_unlock();
> +
> + /*
> + * Account, but do not delay filesystems' metadata IO or IO that is
> + * explicitly marked to not wait or being anticipated, i.e. writes with
> + * wbc->sync_mode set to WBC_SYNC_ALL - fsync() - or journal activity.
> + */
> + if (is_urgent_io(bio))
> + sleep = 0;
> + return sleep;
> +}
> diff --git a/include/linux/blk-io-throttle.h b/include/linux/blk-io-throttle.h
> new file mode 100644
> index 0000000..304c56c
> --- /dev/null
> +++ b/include/linux/blk-io-throttle.h
> @@ -0,0 +1,144 @@
> +#ifndef BLK_IO_THROTTLE_H
> +#define BLK_IO_THROTTLE_H
> +
> +#include <linux/fs.h>
> +#include <linux/jiffies.h>
> +#include <linux/sched.h>
> +#include <linux/cgroup.h>
> +#include <asm/atomic.h>
> +#include <asm/current.h>
> +
> +#define IOTHROTTLE_BANDWIDTH 0
> +#define IOTHROTTLE_IOPS 1
> +#define IOTHROTTLE_FAILCNT 2
> +#define IOTHROTTLE_STAT 3
> +
> +#ifdef CONFIG_CGROUP_IO_THROTTLE
> +
> +static inline bool iothrottle_disabled(void)
> +{
> + if (iothrottle_subsys.disabled)
> + return true;
> + return false;
> +}
> +
> +extern unsigned long long
> +cgroup_io_throttle(struct bio *bio, struct block_device *bdev, ssize_t bytes);
> +
> +extern int iothrottle_make_request(struct bio *bio, unsigned long deadline);
> +
> +int iothrottle_set_page_owner(struct page *page, struct mm_struct *mm);
> +int iothrottle_set_pagedirty_owner(struct page *page, struct mm_struct *mm);
> +int iothrottle_copy_page_owner(struct page *npage, struct page *opage);
> +
> +extern int iothrottle_sync(void);
> +
> +static inline void set_in_aio(void)
> +{
> + atomic_set(¤t->in_aio, 1);
> +}
> +
> +static inline void unset_in_aio(void)
> +{
> + atomic_set(¤t->in_aio, 0);
> +}
> +
> +static inline int is_in_aio(void)
> +{
> + return atomic_read(¤t->in_aio);
> +}
> +
> +static inline unsigned long long
> +get_io_throttle_cnt(struct task_struct *t, int type)
> +{
> + switch (type) {
> + case IOTHROTTLE_BANDWIDTH:
> + return t->io_throttle_bw_cnt;
> + case IOTHROTTLE_IOPS:
> + return t->io_throttle_iops_cnt;
> + }
> + BUG();
> +}
> +
> +static inline unsigned long long
> +get_io_throttle_sleep(struct task_struct *t, int type)
> +{
> + switch (type) {
> + case IOTHROTTLE_BANDWIDTH:
> + return jiffies_to_clock_t(t->io_throttle_bw_sleep);
> + case IOTHROTTLE_IOPS:
> + return jiffies_to_clock_t(t->io_throttle_iops_sleep);
> + }
> + BUG();
> +}
> +#else /* CONFIG_CGROUP_IO_THROTTLE */
> +
> +static inline bool iothrottle_disabled(void)
> +{
> + return true;
> +}
> +
> +static inline unsigned long long
> +cgroup_io_throttle(struct bio *bio, struct block_device *bdev, ssize_t bytes)
> +{
> + return 0;
> +}
> +
> +static inline int
> +iothrottle_make_request(struct bio *bio, unsigned long deadline)
> +{
> + return 0;
> +}
> +
> +static inline int iothrottle_set_page_owner(struct page *page,
> + struct mm_struct *mm)
> +{
> + return 0;
> +}
> +
> +static inline int iothrottle_set_pagedirty_owner(struct page *page,
> + struct mm_struct *mm)
> +{
> + return 0;
> +}
> +
> +static inline int iothrottle_copy_page_owner(struct page *npage,
> + struct page *opage)
> +{
> + return 0;
> +}
> +
> +static inline int iothrottle_sync(void)
> +{
> + return 0;
> +}
> +
> +static inline void set_in_aio(void) { }
> +
> +static inline void unset_in_aio(void) { }
> +
> +static inline int is_in_aio(void)
> +{
> + return 0;
> +}
> +
> +static inline unsigned long long
> +get_io_throttle_cnt(struct task_struct *t, int type)
> +{
> + return 0;
> +}
> +
> +static inline unsigned long long
> +get_io_throttle_sleep(struct task_struct *t, int type)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_CGROUP_IO_THROTTLE */
> +
> +static inline struct block_device *as_to_bdev(struct address_space *mapping)
> +{
> + return (mapping->host && mapping->host->i_sb->s_bdev) ?
> + mapping->host->i_sb->s_bdev : NULL;
> +}
> +
> +#endif /* BLK_IO_THROTTLE_H */
> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> index 9c8d31b..c37cc4b 100644
> --- a/include/linux/cgroup_subsys.h
> +++ b/include/linux/cgroup_subsys.h
> @@ -43,6 +43,12 @@ SUBSYS(mem_cgroup)
>
> /* */
>
> +#ifdef CONFIG_CGROUP_IO_THROTTLE
> +SUBSYS(iothrottle)
> +#endif
> +
> +/* */
> +
> #ifdef CONFIG_CGROUP_DEVICE
> SUBSYS(devices)
> #endif
> diff --git a/init/Kconfig b/init/Kconfig
> index 5428ac7..d496c5f 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -565,6 +565,18 @@ config RESOURCE_COUNTERS
> infrastructure that works with cgroups.
> depends on CGROUPS
>
> +config CGROUP_IO_THROTTLE
> + bool "Enable cgroup I/O throttling"
> + depends on CGROUPS && RESOURCE_COUNTERS && EXPERIMENTAL
> + select MM_OWNER
> + select PAGE_TRACKING
> + help
> + This allows to limit the maximum I/O bandwidth for specific
> + cgroup(s).
> + See Documentation/cgroups/io-throttle.txt for more information.
> +
> + If unsure, say N.
> +
> config CGROUP_MEM_RES_CTLR
> bool "Memory Resource Controller for Control Groups"
> depends on CGROUPS && RESOURCE_COUNTERS
> --
> 1.5.6.3
>
> --
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