Re: [PATCH 2/2] cgroups: introduce timer slack subsystem

[Kirill A. Shutemov]

On Sun, Jan 30, 2011 at 11:59:22AM +0200, Kirill A. Shutsemov wrote:
> From: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
> 
> Provides a way of tasks grouping by timer slack value. Introduces per
> cgroup timer slack value which will override the default timer slack
> value once a task is attached to a cgroup.
> 
> It's useful in mobile devices where certain background apps are
> attached to a cgroup and minimum wakeups are desired.
> 
> Based on patch by Jacob Pan.
> 
> Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
> ---
>  include/linux/cgroup_subsys.h |    6 ++
>  include/linux/init_task.h     |    4 +-
>  init/Kconfig                  |   10 ++++
>  kernel/Makefile               |    1 +
>  kernel/cgroup_timer_slack.c   |  115 +++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 135 insertions(+), 1 deletions(-)
>  create mode 100644 kernel/cgroup_timer_slack.c
> 
> 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/include/linux/init_task.h b/include/linux/init_task.h
> index caa151f..48eca8f 100644
> --- a/include/linux/init_task.h
> +++ b/include/linux/init_task.h
> @@ -124,6 +124,8 @@ extern struct cred init_cred;
>  # define INIT_PERF_EVENTS(tsk)
>  #endif
>  
> +#define TIMER_SLACK_NS_DEFAULT 50000
> +
>  /*
>   *  INIT_TASK is used to set up the first task table, touch at
>   * your own risk!. Base=0, limit=0x1fffff (=2MB)
> @@ -177,7 +179,7 @@ extern struct cred init_cred;
>  	.cpu_timers	= INIT_CPU_TIMERS(tsk.cpu_timers),		\
>  	.fs_excl	= ATOMIC_INIT(0),				\
>  	.pi_lock	= __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock),	\
> -	.timer_slack_ns = 50000, /* 50 usec default slack */		\
> +	.timer_slack_ns = TIMER_SLACK_NS_DEFAULT,			\
>  	.pids = {							\
>  		[PIDTYPE_PID]  = INIT_PID_LINK(PIDTYPE_PID),		\
>  		[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID),		\
> diff --git a/init/Kconfig b/init/Kconfig
> index be788c0..f21b4ce 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 subsystem"
> +	help
> +	  Provides a way of tasks grouping by timer slack value.
> +	  Introduces per cgroup timer slack value which will override
> +	  the default timer slack value once a task is attached to a
> +	  cgroup.
> +	  It's useful in mobile devices where certain background apps
> +	  are attached to a cgroup and minimum wakeups are desired.
> +
>  config CGROUP_DEVICE
>  	bool "Device controller for cgroups"
>  	help
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 353d3fe..0b60239 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..9f3c370
> --- /dev/null
> +++ b/kernel/cgroup_timer_slack.c
> @@ -0,0 +1,115 @@
> +#include <linux/cgroup.h>
> +#include <linux/init_task.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +static struct cgroup_subsys timer_slack_subsys;

s/static //

> +struct timer_slack_cgroup {
> +	struct cgroup_subsys_state css;
> +	unsigned long timer_slack_ns;
> +};
> +
> +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 struct cgroup_subsys_state *
> +tslack_cgroup_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
> +{
> +	struct timer_slack_cgroup *tslack_cgroup;
> +	struct cgroup *parent = cgroup->parent;
> +
> +	tslack_cgroup = kmalloc(sizeof(*tslack_cgroup), GFP_KERNEL);
> +	if (!tslack_cgroup)
> +		return ERR_PTR(-ENOMEM);
> +
> +	if (parent)
> +		tslack_cgroup->timer_slack_ns =
> +			cgroup_to_tslack_cgroup(parent)->timer_slack_ns;
> +	else
> +		tslack_cgroup->timer_slack_ns = TIMER_SLACK_NS_DEFAULT;
> +
> +	return &tslack_cgroup->css;
> +}
> +
> +static void tslack_cgroup_destroy(struct cgroup_subsys *subsys,
> +		struct cgroup *cgroup)
> +{
> +	kfree(cgroup_to_tslack_cgroup(cgroup));
> +}
> +
> +static void tslack_cgroup_attach(struct cgroup_subsys *subsys,
> +		struct cgroup *cgroup, struct cgroup *prev,
> +		struct task_struct *tsk, bool threadgroup)
> +{
> +	struct timer_slack_cgroup *tslack_cgroup;
> +
> +	tslack_cgroup = cgroup_to_tslack_cgroup(cgroup);
> +	task_lock(tsk);
> +	tsk->timer_slack_ns = tslack_cgroup->timer_slack_ns;
> +	task_unlock(tsk);
> +}
> +
> +static u64 tslack_read_slack_ns(struct cgroup *cgroup, struct cftype *cft)
> +{
> +       return cgroup_to_tslack_cgroup(cgroup)->timer_slack_ns;
> +}
> +
> +static int tslack_write_slack_ns(struct cgroup *cgroup, struct cftype *cft,
> +		u64 val)
> +{
> +	struct cgroup_iter it;
> +	struct task_struct *task;
> +
> +	if (!val)
> +		return -EINVAL;
> +
> +	cgroup_to_tslack_cgroup(cgroup)->timer_slack_ns = val;
> +
> +	/* change timer slack value for all tasks in the cgroup */
> +	cgroup_iter_start(cgroup, &it);
> +	while ((task = cgroup_iter_next(cgroup, &it)))
> +		task->timer_slack_ns = val;
> +	cgroup_iter_end(cgroup, &it);
> +
> +	return 0;
> +}
> +
> +static struct cftype cft_timer_slack = {
> +	.name = "slack_ns",
> +	.read_u64 = tslack_read_slack_ns,
> +	.write_u64 = tslack_write_slack_ns,
> +};
> +
> +static int tslack_cgroup_populate(struct cgroup_subsys *subsys,
> +		struct cgroup *cgroup)
> +{
> +	return cgroup_add_file(cgroup, subsys, &cft_timer_slack);
> +}
> +
> +static struct cgroup_subsys timer_slack_subsys = {

ditto.

> +	.name = "timer_slack",
> +	.module = THIS_MODULE,
> +	.create = tslack_cgroup_create,
> +	.destroy = tslack_cgroup_destroy,
> +	.attach = tslack_cgroup_attach,
> +	.populate = tslack_cgroup_populate,
> +};
> +
> +static int __init init_cgroup_timer_slack(void)
> +{
> +	return cgroup_load_subsys(&timer_slack_subsys);
> +}
> +
> +static void __exit exit_cgroup_timer_slack(void)
> +{
> +	cgroup_unload_subsys(&timer_slack_subsys);
> +}
> +
> +module_init(init_cgroup_timer_slack);
> +module_exit(exit_cgroup_timer_slack);
> +MODULE_LICENSE("GPL");
> -- 
> 1.7.3.5
> 

-- 
 Kirill A. Shutemov
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