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Subject[PATCH, v2 2/2] cgroups: introduce timer slack subsystem
Date
From: Kirill A. Shutemov <kirill@shutemov.name>

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@shutemov.name>
---

Changelog:
v2:
- fixed with CONFIG_CGROUP_TIMER_SLACK=y

---
include/linux/cgroup_subsys.h | 6 ++
include/linux/init_task.h | 4 +-
init/Kconfig | 10 ++++
kernel/Makefile | 1 +
kernel/cgroup_timer_slack.c | 116 +++++++++++++++++++++++++++++++++++++++++
5 files changed, 136 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..daa452d
--- /dev/null
+++ b/kernel/cgroup_timer_slack.c
@@ -0,0 +1,116 @@
+#include <linux/cgroup.h>
+#include <linux/init_task.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+struct cgroup_subsys timer_slack_subsys;
+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);
+}
+
+struct cgroup_subsys timer_slack_subsys = {
+ .name = "timer_slack",
+ .module = THIS_MODULE,
+ .subsys_id = timer_slack_subsys_id,
+ .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


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