From: Kirill A. Shutemov <[email protected]> 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 <[email protected]> Signed-off-by: Kirill A. Shutemov <[email protected]> --- 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, timer_slack_subsys.subsys_id); + tslack_cgroup = container_of(css, struct timer_slack_cgroup, css); + rcu_read_unlock(); + + if (!is_timer_slack_allowed(tslack_cgroup, slack_ns)) + return notifier_from_errno(-EPERM); + return NOTIFY_OK; +} + +static struct notifier_block cgroup_timer_slack_nb = { + .notifier_call = cgroup_timer_slack_check, +}; + +static struct cgroup_subsys_state * +tslack_cgroup_create(struct cgroup_subsys *subsys, struct cgroup *cgroup) +{ + struct timer_slack_cgroup *tslack_cgroup; + + tslack_cgroup = kmalloc(sizeof(*tslack_cgroup), GFP_KERNEL); + if (!tslack_cgroup) + return ERR_PTR(-ENOMEM); + + if (cgroup->parent) { + struct timer_slack_cgroup *parent; + parent = cgroup_to_tslack_cgroup(cgroup->parent); + tslack_cgroup->min_slack_ns = parent->min_slack_ns; + tslack_cgroup->max_slack_ns = parent->max_slack_ns; + } else { + tslack_cgroup->min_slack_ns = 0UL; + tslack_cgroup->max_slack_ns = ULONG_MAX; + } + + return &tslack_cgroup->css; +} + +static void tslack_cgroup_destroy(struct cgroup_subsys *subsys, + struct cgroup *cgroup) +{ + kfree(cgroup_to_tslack_cgroup(cgroup)); +} + +/* + * Adjust ->timer_slack_ns and ->default_max_slack_ns of the task to fit + * limits of the cgroup. + */ +static void tslack_adjust_task(struct timer_slack_cgroup *tslack_cgroup, + struct task_struct *tsk) +{ + if (tslack_cgroup->min_slack_ns > tsk->timer_slack_ns) + tsk->timer_slack_ns = tslack_cgroup->min_slack_ns; + else if (tslack_cgroup->max_slack_ns < tsk->timer_slack_ns) + tsk->timer_slack_ns = tslack_cgroup->max_slack_ns; + + if (tslack_cgroup->min_slack_ns > tsk->default_timer_slack_ns) + tsk->default_timer_slack_ns = tslack_cgroup->min_slack_ns; + else if (tslack_cgroup->max_slack_ns < tsk->default_timer_slack_ns) + tsk->default_timer_slack_ns = tslack_cgroup->max_slack_ns; +} + +static void tslack_cgroup_attach(struct cgroup_subsys *subsys, + struct cgroup *cgroup, struct cgroup *prev, + struct task_struct *tsk, bool threadgroup) +{ + tslack_adjust_task(cgroup_to_tslack_cgroup(cgroup), tsk); +} + +static int tslack_write_set_slack_ns(struct cgroup *cgroup, struct cftype *cft, + u64 val) +{ + struct timer_slack_cgroup *tslack_cgroup; + struct cgroup_iter it; + struct task_struct *task; + + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); + if (!is_timer_slack_allowed(cgroup_to_tslack_cgroup(cgroup), val)) + return -EPERM; + + /* 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 u64 tslack_read_range(struct cgroup *cgroup, struct cftype *cft) +{ + struct timer_slack_cgroup *tslack_cgroup; + + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); + switch (cft->private) { + case TIMER_SLACK_MIN: + return tslack_cgroup->min_slack_ns; + case TIMER_SLACK_MAX: + return tslack_cgroup->max_slack_ns; + default: + BUG(); + } +} + +static int validate_change(struct cgroup *cgroup, u64 val, int type) +{ + struct timer_slack_cgroup *tslack_cgroup, *child; + struct cgroup *cur; + + BUG_ON(type != TIMER_SLACK_MIN && type != TIMER_SLACK_MAX); + + if (val > ULONG_MAX) + return -EINVAL; + + if (cgroup->parent) { + struct timer_slack_cgroup *parent; + parent = cgroup_to_tslack_cgroup(cgroup->parent); + if (!is_timer_slack_allowed(parent, val)) + return -EPERM; + } + + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); + if (type == TIMER_SLACK_MIN && val > tslack_cgroup->max_slack_ns) + return -EINVAL; + if (type == TIMER_SLACK_MAX && val < tslack_cgroup->min_slack_ns) + return -EINVAL; + + list_for_each_entry(cur, &cgroup->children, sibling) { + child = cgroup_to_tslack_cgroup(cur); + if (type == TIMER_SLACK_MIN && val > child->min_slack_ns) + return -EBUSY; + if (type == TIMER_SLACK_MAX && val < child->max_slack_ns) + return -EBUSY; + } + + return 0; +} + +static int tslack_write_range(struct cgroup *cgroup, struct cftype *cft, + u64 val) +{ + struct timer_slack_cgroup *tslack_cgroup; + struct cgroup_iter it; + struct task_struct *task; + int err; + + err = validate_change(cgroup, val, cft->private); + if (err) + return err; + + tslack_cgroup = cgroup_to_tslack_cgroup(cgroup); + if (cft->private == TIMER_SLACK_MIN) + tslack_cgroup->min_slack_ns = val; + else + tslack_cgroup->max_slack_ns = val; + + /* + * Adjust timer slack value for all tasks in the cgroup to fit + * min-max range. + */ + cgroup_iter_start(cgroup, &it); + while ((task = cgroup_iter_next(cgroup, &it))) + tslack_adjust_task(tslack_cgroup, task); + cgroup_iter_end(cgroup, &it); + + return 0; +} + +static struct cftype files[] = { + { + .name = "set_slack_ns", + .write_u64 = tslack_write_set_slack_ns, + }, + { + .name = "min_slack_ns", + .private = TIMER_SLACK_MIN, + .read_u64 = tslack_read_range, + .write_u64 = tslack_write_range, + }, + { + .name = "max_slack_ns", + .private = TIMER_SLACK_MAX, + .read_u64 = tslack_read_range, + .write_u64 = tslack_write_range, + }, +}; + +static int tslack_cgroup_populate(struct cgroup_subsys *subsys, + struct cgroup *cgroup) +{ + return cgroup_add_files(cgroup, subsys, files, ARRAY_SIZE(files)); +} + +struct cgroup_subsys timer_slack_subsys = { + .name = "timer_slack", + .module = THIS_MODULE, +#ifndef CONFIG_CGROUP_TIMER_SLACK_MODULE + .subsys_id = timer_slack_subsys_id, +#endif + .create = tslack_cgroup_create, + .destroy = tslack_cgroup_destroy, + .attach = tslack_cgroup_attach, + .populate = tslack_cgroup_populate, +}; + +static int __init init_cgroup_timer_slack(void) +{ + int err; + + err = register_timer_slack_notifier(&cgroup_timer_slack_nb); + if (err) + return err; + + err = cgroup_load_subsys(&timer_slack_subsys); + if (err) + unregister_timer_slack_notifier(&cgroup_timer_slack_nb); + + return err; +} + +static void __exit exit_cgroup_timer_slack(void) +{ + unregister_timer_slack_notifier(&cgroup_timer_slack_nb); + cgroup_unload_subsys(&timer_slack_subsys); +} + +module_init(init_cgroup_timer_slack); +module_exit(exit_cgroup_timer_slack); +MODULE_LICENSE("GPL"); -- 1.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
