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Date: Fri, 18 Jan 2008 16:50:57 +0100 (MET)
From: Andrea Righi <righiandr@...rs.sourceforge.net>
To: Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Paul Menage <menage@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cgroup: limit block I/O bandwidth
Andrea Righi wrote:
[snip]
> +static ssize_t iothrottle_read(struct cgroup *cont, struct cftype *cft,
> + struct file *file, char __user *buf,
> + size_t nbytes, loff_t *ppos)
> +{
> + ssize_t count, ret;
> + unsigned long delta, iorate, req, last_request;
> + struct iothrottle *iot;
> + char *page;
> +
> + page = (char *)__get_free_page(GFP_TEMPORARY);
> + if (!page)
> + return -ENOMEM;
> +
> + cgroup_lock();
> + if (cgroup_is_removed(cont)) {
> + cgroup_unlock();
> + ret = -ENODEV;
> + goto out;
> + }
> +
> + iot = cgroup_to_iothrottle(cont);
> + spin_lock_irq(&iot->lock);
> +
> + delta = (long)jiffies - (long)iot->last_request;
> + iorate = iot->iorate;
> + req = iot->req << 1;
> + last_request = iot->last_request;
> +
> + spin_unlock_irq(&iot->lock);
> + cgroup_unlock();
> +
> + /* print additional debugging stuff */
> + count = sprintf(page, " io-rate: %lu KiB/sec\n"
> + " requested: %lu KiB\n"
> + "last_request: %lu jiffies\n"
> + " delta: %lu jiffies\n",
> + iorate, req << 1, last_request, delta);
^^^^^^^^
Argh! just found a (minor) bug here... :-( the variable req is already
translated from sectors/sec in KB/sec here, so there's no need to lshift
it again (or better there's no need to shift it before).
Sorry for that. Fixed patch is below.
Signed-off-by: Andrea Righi <a.righi@...eca.it>
---
diff -urpN linux-2.6.24-rc8/block/io-throttle.c linux-2.6.24-rc8-cgroup-io-throttling/block/io-throttle.c
--- linux-2.6.24-rc8/block/io-throttle.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/block/io-throttle.c 2008-01-18 16:14:40.000000000 +0100
@@ -0,0 +1,250 @@
+/*
+ * 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 <a.righi@...eca.it>
+ */
+
+#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/spinlock.h>
+#include <linux/io-throttle.h>
+
+struct iothrottle {
+ struct cgroup_subsys_state css;
+ spinlock_t lock;
+ unsigned long iorate;
+ unsigned long req;
+ unsigned long last_request;
+};
+
+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);
+}
+
+/*
+ * Rules: you can only create a cgroup if:
+ * 1. you are capable(CAP_SYS_ADMIN)
+ * 2. the target cgroup is a descendant of your own cgroup
+ *
+ * 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;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ if (!cgroup_is_descendant(cont))
+ return ERR_PTR(-EPERM);
+
+ iot = kzalloc(sizeof(struct iothrottle), GFP_KERNEL);
+ if (unlikely(!iot))
+ return ERR_PTR(-ENOMEM);
+
+ spin_lock_init(&iot->lock);
+ iot->last_request = jiffies;
+
+ return &iot->css;
+}
+
+/*
+ * Note: called from kernel/cgroup.c with cgroup_lock() held.
+ */
+static void iothrottle_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
+{
+ kfree(cgroup_to_iothrottle(cont));
+}
+
+static ssize_t iothrottle_read(struct cgroup *cont, struct cftype *cft,
+ struct file *file, char __user *buf,
+ size_t nbytes, loff_t *ppos)
+{
+ ssize_t count, ret;
+ unsigned long delta, iorate, req, last_request;
+ struct iothrottle *iot;
+ char *page;
+
+ page = (char *)__get_free_page(GFP_TEMPORARY);
+ if (!page)
+ return -ENOMEM;
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ cgroup_unlock();
+ ret = -ENODEV;
+ goto out;
+ }
+
+ iot = cgroup_to_iothrottle(cont);
+ spin_lock_irq(&iot->lock);
+
+ delta = (long)jiffies - (long)iot->last_request;
+ iorate = iot->iorate;
+ req = iot->req;
+ last_request = iot->last_request;
+
+ spin_unlock_irq(&iot->lock);
+ cgroup_unlock();
+
+ /* print additional debugging stuff */
+ count = sprintf(page, " io-rate: %lu KiB/sec\n"
+ " requested: %lu KiB\n"
+ "last_request: %lu jiffies\n"
+ " delta: %lu jiffies\n",
+ iorate, req << 1, last_request, delta);
+
+ ret = simple_read_from_buffer(buf, nbytes, ppos, page, count);
+
+out:
+ free_page((unsigned long)page);
+ return ret;
+}
+
+static int iothrottle_write_uint(struct cgroup *cont, struct cftype *cft,
+ u64 val)
+{
+ struct iothrottle *iot;
+ int ret = 0;
+
+ cgroup_lock();
+ if (cgroup_is_removed(cont)) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ iot = cgroup_to_iothrottle(cont);
+
+ spin_lock_irq(&iot->lock);
+ iot->iorate = (unsigned long)val;
+ spin_unlock_irq(&iot->lock);
+
+out:
+ cgroup_unlock();
+ return ret;
+}
+
+static struct cftype files[] = {
+ {
+ .name = "io-rate",
+ .read = iothrottle_read,
+ .write_uint = iothrottle_write_uint,
+ },
+};
+
+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 = "io-throttle",
+ .create = iothrottle_create,
+ .destroy = iothrottle_destroy,
+ .populate = iothrottle_populate,
+ .subsys_id = iothrottle_subsys_id,
+};
+
+void io_throttle(int nr_sectors)
+{
+ struct iothrottle *iot;
+ unsigned long delta, n;
+ long sleep;
+
+ cgroup_lock();
+ iot = task_to_iothrottle(current);
+ if (!iot)
+ goto out;
+
+ spin_lock_irq(&iot->lock);
+ if (!iot->iorate)
+ goto out2;
+
+ /*
+ * The concept is the following: evaluate the actual I/O rate of a
+ * process, looking at the sectors requested over the time elapsed from
+ * the last request. If the actual I/O rate is beyond the maximum
+ * allowed I/O rate then sleep the current task for the correct amount
+ * of time, in order to reduce the actual I/O rate under the allowed
+ * limit.
+ *
+ * The time to sleep is evaluated as:
+ *
+ * sleep = (sectors_requested / allowed_iorate) - time_elapsed
+ */
+ delta = (long)jiffies - (long)iot->last_request;
+ iot->req += nr_sectors;
+ n = iot->req / iot->iorate;
+
+ spin_unlock_irq(&iot->lock);
+ cgroup_unlock();
+
+ /*
+ * If it's not possible to evaluate delta (due to a too small interval
+ * of time between two requests) or n (due to a too small request),
+ * account the requested sectors in iot->req and sum them to the
+ * sectors of the next request.
+ */
+ if (!delta || !n)
+ return;
+
+ /*
+ * Convert n in jiffies (remember that iot->iorate is in KB/s and we
+ * need to convert it in sectors/jiffies)
+ */
+ sleep = msecs_to_jiffies(n * 1000 / 2) - delta;
+ if (sleep > 0) {
+ pr_debug("io-throttle: task %p (%s) must sleep %lu jiffies\n",
+ current, current->comm, sleep);
+ schedule_timeout_uninterruptible(sleep);
+ }
+
+ /*
+ * Note: iothrottle element could be changed during the sleep, so
+ * we must refresh it before resetting statistics.
+ */
+ cgroup_lock();
+ iot = task_to_iothrottle(current);
+ if (!iot)
+ goto out;
+
+ spin_lock_irq(&iot->lock);
+ iot->req = 0;
+ iot->last_request = jiffies;
+out2:
+ spin_unlock_irq(&iot->lock);
+out:
+ cgroup_unlock();
+}
+EXPORT_SYMBOL(io_throttle);
diff -urpN linux-2.6.24-rc8/block/ll_rw_blk.c linux-2.6.24-rc8-cgroup-io-throttling/block/ll_rw_blk.c
--- linux-2.6.24-rc8/block/ll_rw_blk.c 2008-01-16 05:22:48.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/block/ll_rw_blk.c 2008-01-18 16:14:09.000000000 +0100
@@ -31,6 +31,7 @@
#include <linux/blktrace_api.h>
#include <linux/fault-inject.h>
#include <linux/scatterlist.h>
+#include <linux/io-throttle.h>
/*
* for max sense size
@@ -3221,6 +3222,8 @@ static inline void __generic_make_reques
if (bio_check_eod(bio, nr_sectors))
goto end_io;
+ io_throttle(nr_sectors);
+
/*
* Resolve the mapping until finished. (drivers are
* still free to implement/resolve their own stacking
diff -urpN linux-2.6.24-rc8/block/Makefile linux-2.6.24-rc8-cgroup-io-throttling/block/Makefile
--- linux-2.6.24-rc8/block/Makefile 2008-01-16 05:22:48.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/block/Makefile 2008-01-18 16:14:09.000000000 +0100
@@ -12,3 +12,5 @@ obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched
obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
obj-$(CONFIG_BLOCK_COMPAT) += compat_ioctl.o
+
+obj-$(CONFIG_CGROUP_IO_THROTTLE) += io-throttle.o
diff -urpN linux-2.6.24-rc8/include/linux/cgroup_subsys.h linux-2.6.24-rc8-cgroup-io-throttling/include/linux/cgroup_subsys.h
--- linux-2.6.24-rc8/include/linux/cgroup_subsys.h 2008-01-16 05:22:48.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/include/linux/cgroup_subsys.h 2008-01-18 16:14:09.000000000 +0100
@@ -37,3 +37,9 @@ SUBSYS(cpuacct)
/* */
+#ifdef CONFIG_CGROUP_IO_THROTTLE
+SUBSYS(iothrottle)
+#endif
+
+/* */
+
diff -urpN linux-2.6.24-rc8/include/linux/io-throttle.h linux-2.6.24-rc8-cgroup-io-throttling/include/linux/io-throttle.h
--- linux-2.6.24-rc8/include/linux/io-throttle.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/include/linux/io-throttle.h 2008-01-18 16:14:09.000000000 +0100
@@ -0,0 +1,10 @@
+#ifndef IO_THROTTLE_H
+#define IO_THROTTLE_H
+
+#ifdef CONFIG_CGROUP_IO_THROTTLE
+extern void io_throttle(int nr_sectors);
+#else
+static inline void io_throttle(int nr_sectors) { }
+#endif /* CONFIG_CGROUP_IO_THROTTLE */
+
+#endif
diff -urpN linux-2.6.24-rc8/init/Kconfig linux-2.6.24-rc8-cgroup-io-throttling/init/Kconfig
--- linux-2.6.24-rc8/init/Kconfig 2008-01-16 05:22:48.000000000 +0100
+++ linux-2.6.24-rc8-cgroup-io-throttling/init/Kconfig 2008-01-18 16:14:09.000000000 +0100
@@ -313,6 +313,15 @@ config CGROUP_NS
for instance virtual servers and checkpoint/restart
jobs.
+config CGROUP_IO_THROTTLE
+ bool "Enable cgroup I/O throttling (EXPERIMENTAL)"
+ depends on EXPERIMENTAL && CGROUPS
+ help
+ This allows to limit the maximum I/O bandwidth for specific
+ cgroup(s).
+
+ Say N if unsure.
+
config CPUSETS
bool "Cpuset support"
depends on SMP && CGROUPS
--
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