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Re: [PATCH, v6 3/3] cgroups: introduce timer slack controller [message #41712 is a reply to message #41682] Mon, 14 February 2011 22:59 Go to previous messageGo to previous message
Kirill A. Shutsemov is currently offline  Kirill A. Shutsemov
Messages: 32
Registered: February 2011
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On Mon, Feb 14, 2011 at 05:59:26AM -0800, Matt Helsley wrote:
> On Mon, Feb 14, 2011 at 03:06:27PM +0200, Kirill A. Shutsemov wrote:
> > From: Kirill A. Shutemov <kirill@shutemov.name>
> >
> > Every task_struct has timer_slack_ns value. This value uses to round up
> > poll() and select() timeout values. This feature can be useful in
> > mobile environment where combined wakeups are desired.
> >
> > cgroup subsys "timer_slack" implement timer slack controller. It
> > provides a way to group tasks by timer slack value and manage the
> > value of group's tasks.
> >
> > Idea-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> > ---
> > Documentation/cgroups/timer_slack.txt | 93 +++++++++++
> > include/linux/cgroup_subsys.h | 6 +
> > init/Kconfig | 10 ++
> > kernel/Makefile | 1 +
> > kernel/cgroup_timer_slack.c | 285 +++++++++++++++++++++++++++++++++
> > 5 files changed, 395 insertions(+), 0 deletions(-)
> > create mode 100644 Documentation/cgroups/timer_slack.txt
> > create mode 100644 kernel/cgroup_timer_slack.c
> >
> > diff --git a/Documentation/cgroups/timer_slack.txt b/Documentation/cgroups/timer_slack.txt
> > new file mode 100644
> > index 0000000..e7ec2f3
> > --- /dev/null
> > +++ b/Documentation/cgroups/timer_slack.txt
> > @@ -0,0 +1,93 @@
> > +Timer Slack Controller
> > +=====================
> > +
> > +Overview
> > +--------
> > +
> > +Every task_struct has timer_slack_ns value. This value uses to round up
> > +poll() and select() timeout values. This feature can be useful in
> > +mobile environment where combined wakeups are desired.
> > +
> > +cgroup subsys "timer_slack" implement timer slack controller. It
> > +provides a way to group tasks by timer slack value and manage the
> > +value of group's tasks.
> > +
> > +
> > +User interface
> > +--------------
> > +
> > +To get timer slack controller functionality you need to enable it in
> > +kernel configuration:
> > +
> > +CONFIG_CGROUP_TIMER_SLACK=y
> > +
> > +or if you want to compile it as module:
> > +
> > +CONFIG_CGROUP_TIMER_SLACK=m
> > +
> > +The controller provides three files in cgroup directory:
> > +
> > +# mount -t cgroup -o timer_slack none /sys/fs/cgroup
> > +# ls /sys/fs/cgroup/timer_slack.*
> > +/sys/fs/cgroup/timer_slack.max_slack_ns
> > +/sys/fs/cgroup/timer_slack.min_slack_ns
> > +/sys/fs/cgroup/timer_slack.set_slack_ns
> > +
> > +timer_slack.min_slack_ns and timer_slack.set_slack_ns specify allowed
> > +range of timer slack for tasks in cgroup. By default it unlimited:
> > +
> > +# cat /sys/fs/cgroup/timer_slack.min_slack_ns
> > +0
> > +# cat /sys/fs/cgroup/timer_slack.max_slack_ns
> > +4294967295
> > +
> > +You can specify limits you want:
> > +
> > +# echo 50000 > /sys/fs/cgroup/timer_slack.min_slack_ns
> > +# echo 1000000 > /sys/fs/cgroup/timer_slack.max_slack_ns
> > +# cat /sys/fs/cgroup/timer_slack.{min,max}_slack_ns
> > +50000
> > +1000000
> > +
> > +Timer slack value of all tasks of the cgroup will be adjusted to fit
> > +min-max range.
> > +
> > +If a task will try to call prctl() to change timer slack value out of
> > +the range it get -EPERM.
> > +
> > +You can change timer slack value of all tasks of the cgroup at once:
> > +
> > +# echo 70000 > /sys/fs/cgroup/timer_slack.set_slack_ns
> > +
> > +Timer slack controller supports hierarchical groups. The only rule:
> > +parent's limit range should be wider or equal to child's. Sibling
> > +cgroups can have overlapping min-max range.
> > +
> > + (root: 50000 - 1000000)
> > + / \
> > + (a: 50000 - 50000) (b: 500000 - 1000000)
> > + / \
> > + (c: 500000 - 900000) (d: 700000 - 800000)
> > +
> > +# mkdir /sys/fs/cgroup/a
> > +# echo 50000 > /sys/fs/cgroup/a/timer_slack.max_slack_ns
> > +# cat /sys/fs/cgroup/a/timer_slack.{min,max}_slack_ns
> > +50000
> > +50000
> > +# mkdir /sys/fs/cgroup/b
> > +# echo 500000 > /sys/fs/cgroup/b/timer_slack.min_slack_ns
> > +# cat /sys/fs/cgroup/b/timer_slack.{min,max}_slack_ns
> > +500000
> > +1000000
> > +# mkdir /sys/fs/cgroup/b/c
> > +# echo 900000 > /sys/fs/cgroup/b/c/timer_slack.max_slack_ns
> > +# cat /sys/fs/cgroup/b/c/timer_slack.{min,max}_slack_ns
> > +500000
> > +900000
> > +# mkdir /sys/fs/cgroup/b/d
> > +# echo 700000 > /sys/fs/cgroup/b/d/timer_slack.min_slack_ns
> > +# echo 800000 > /sys/fs/cgroup/b/d/timer_slack.max_slack_ns
> > +# cat /sys/fs/cgroup/b/d/timer_slack.{min,max}_slack_ns
> > +700000
> > +800000
> > +
> > diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> > index ccefff0..e399228 100644
> > --- a/include/linux/cgroup_subsys.h
> > +++ b/include/linux/cgroup_subsys.h
> > @@ -66,3 +66,9 @@ SUBSYS(blkio)
> > #endif
> >
> > /* */
> > +
> > +#ifdef CONFIG_CGROUP_TIMER_SLACK
> > +SUBSYS(timer_slack)
> > +#endif
> > +
> > +/* */
> > diff --git a/init/Kconfig b/init/Kconfig
> > index be788c0..bb54ae9 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -596,6 +596,16 @@ config CGROUP_FREEZER
> > Provides a way to freeze and unfreeze all tasks in a
> > cgroup.
> >
> > +config CGROUP_TIMER_SLACK
> > + tristate "Timer slack cgroup controller"
> > + help
> > + Provides a way of tasks grouping by timer slack value.
> > + Every timer slack cgroup has min and max slack value. Task's
> > + timer slack value will be adjusted to fit min-max range once
> > + the task attached to the cgroup.
> > + It's useful in mobile devices where certain background apps
> > + are attached to a cgroup and combined wakeups are desired.
> > +
> > config CGROUP_DEVICE
> > bool "Device controller for cgroups"
> > help
> > diff --git a/kernel/Makefile b/kernel/Makefile
> > index aa43e63..0e660c5 100644
> > --- a/kernel/Makefile
> > +++ b/kernel/Makefile
> > @@ -61,6 +61,7 @@ obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
> > obj-$(CONFIG_COMPAT) += compat.o
> > obj-$(CONFIG_CGROUPS) += cgroup.o
> > obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
> > +obj-$(CONFIG_CGROUP_TIMER_SLACK) += cgroup_timer_slack.o
> > obj-$(CONFIG_CPUSETS) += cpuset.o
> > obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
> > obj-$(CONFIG_UTS_NS) += utsname.o
> > diff --git a/kernel/cgroup_timer_slack.c b/kernel/cgroup_timer_slack.c
> > new file mode 100644
> > index 0000000..ec63700
> > --- /dev/null
> > +++ b/kernel/cgroup_timer_slack.c
> > @@ -0,0 +1,285 @@
> > +/*
> > + * cgroup_timer_slack.c - control group timer slack subsystem
> > + *
> > + * Copyright Nokia Corparation, 2011
> > + * Author: Kirill A. Shutemov
> > + *
> > + * 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.
> > + */
> > +#include <linux/cgroup.h>
> > +#include <linux/init_task.h>
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/rcupdate.h>
> > +
> > +struct cgroup_subsys timer_slack_subsys;
> > +struct timer_slack_cgroup {
> > + struct cgroup_subsys_state css;
> > + unsigned long min_slack_ns;
> > + unsigned long max_slack_ns;
> > +};
> > +
> > +enum {
> > + TIMER_SLACK_MIN,
> > + TIMER_SLACK_MAX,
> > +};
> > +
> > +static struct timer_slack_cgroup *cgroup_to_tslack_cgroup(struct cgroup *cgroup)
> > +{
> > + struct cgroup_subsys_state *css;
> > +
> > + css = cgroup_subsys_state(cgroup, timer_slack_subsys.subsys_id);
> > + return container_of(css, struct timer_slack_cgroup, css);
> > +}
> > +
> > +static int is_timer_slack_allowed(struct timer_slack_cgroup *tslack_cgroup,
> > + unsigned long slack_ns)
> > +{
> > + if (slack_ns < tslack_cgroup->min_slack_ns ||
> > + slack_ns > tslack_cgroup->max_slack_ns)
> > + return false;
> > + return true;
> > +}
> > +
> > +static int cgroup_timer_slack_check(struct notifier_block *nb,
> > + unsigned long slack_ns, void *data)
> > +{
> > + struct cgroup_subsys_state *css;
> > + struct timer_slack_cgroup *tslack_cgroup;
> > +
> > + /* XXX: lockdep false positive? */
> > + rcu_read_lock();
> > + css = task_subsys_state(current, ...

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