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Date: Thu, 3 Mar 2011 16:19:07 +0200
From: "Kirill A. Shutsemov" <kirill@...temov.name>
To: Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>
Cc: containers@...ts.linux-foundation.org,
jacob.jun.pan@...ux.intel.com,
Arjan van de Ven <arjan@...ux.intel.com>,
linux-kernel@...r.kernel.org, Matt Helsley <matthltc@...ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-api@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
"Kirill A. Shutemov" <kirill@...temov.name>
Subject: [PATCH, v8 3/3] cgroups: introduce timer slack controller
From: Kirill A. Shutemov <kirill@...temov.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 set minimal timer slack value for a group of tasks.
If a task belongs to a cgroup with minimal timer slack value higher than
task's value, cgroup's value will be applied.
Idea-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
---
Documentation/cgroups/timer_slack.txt | 64 +++++++++++++++++
include/linux/cgroup_subsys.h | 6 ++
include/linux/sched.h | 4 +
init/Kconfig | 8 ++
kernel/Makefile | 1 +
kernel/cgroup_timer_slack.c | 124 +++++++++++++++++++++++++++++++++
6 files changed, 207 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..b1494ff
--- /dev/null
+++ b/Documentation/cgroups/timer_slack.txt
@@ -0,0 +1,64 @@
+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" implements timer slack controller. It
+provides a way to set minimal timer slack value for a group of tasks.
+If a task belongs to a cgroup with minimal timer slack value higher than
+task's value, cgroup's value will be applied.
+
+User interface
+--------------
+
+To get timer slack controller functionality you need to enable it in
+kernel configuration:
+
+CONFIG_CGROUP_TIMER_SLACK=y
+
+The controller provides two files:
+
+# mount -t cgroup -o timer_slack none /sys/fs/cgroup
+# ls /sys/fs/cgroup/timer_slack.*
+/sys/fs/cgroup/timer_slack.effective_slack_ns
+/sys/fs/cgroup/timer_slack.min_slack_ns
+
+By default timer_slack.min_slack_ns is 0:
+
+# cat /sys/fs/cgroup/timer_slack.min_slack_ns
+0
+
+You can set it to some value:
+
+# echo 50000 > /sys/fs/cgroup/timer_slack.min_slack_ns
+# cat /sys/fs/cgroup/timer_slack.min_slack_ns
+50000
+
+Tasks still can set task's value below 50000 using prctl(), but in this
+case cgroup's value will be applied.
+
+Timer slack controller supports hierarchical groups.
+
+# mkdir /sys/fs/cgroup/a
+# cat /sys/fs/cgroup/a/timer_slack.min_slack_ns
+50000
+# echo 70000 > /sys/fs/cgroup/a/timer_slack.min_slack_ns
+# cat /sys/fs/cgroup/a/timer_slack.min_slack_ns
+70000
+
+You can set any value you want, but effective value will the highest value
+up by hierarchy. You can see effective timer slack value for the cgroup from
+timer_slack.effective_slack_ns file:
+
+# cat /sys/fs/cgroup/a/timer_slack.effective_slack_ns
+70000
+# echo 100000 > /sys/fs/cgroup/timer_slack.min_slack_ns
+# cat /sys/fs/cgroup/a/timer_slack.min_slack_ns
+70000
+# cat /sys/fs/cgroup/a/timer_slack.effective_slack_ns
+100000
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/sched.h b/include/linux/sched.h
index 44f6f55..c10da5d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2620,11 +2620,15 @@ static inline unsigned long rlimit_max(unsigned int limit)
return task_rlimit_max(current, limit);
}
+#ifdef CONFIG_CGROUP_TIMER_SLACK
+extern unsigned long task_get_effective_timer_slack(struct task_struct *tsk);
+#else
static inline unsigned long task_get_effective_timer_slack(
struct task_struct *tsk)
{
return tsk->timer_slack_ns;
}
+#endif
#endif /* __KERNEL__ */
diff --git a/init/Kconfig b/init/Kconfig
index be788c0..bbc4d9c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -596,6 +596,14 @@ config CGROUP_FREEZER
Provides a way to freeze and unfreeze all tasks in a
cgroup.
+config CGROUP_TIMER_SLACK
+ bool "Timer slack cgroup controller"
+ help
+ Provides a way to set minimal timer slack value for tasks in
+ a 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 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..9824807
--- /dev/null
+++ b/kernel/cgroup_timer_slack.c
@@ -0,0 +1,124 @@
+/*
+ * 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/slab.h>
+
+struct cgroup_subsys timer_slack_subsys;
+struct tslack_cgroup {
+ struct cgroup_subsys_state css;
+ unsigned long min_slack_ns;
+};
+
+static struct tslack_cgroup *cgroup_to_tslack(struct cgroup *cgroup)
+{
+ struct cgroup_subsys_state *css;
+
+ css = cgroup_subsys_state(cgroup, timer_slack_subsys.subsys_id);
+ return container_of(css, struct tslack_cgroup, css);
+}
+
+static struct cgroup_subsys_state *tslack_create(struct cgroup_subsys *subsys,
+ struct cgroup *cgroup)
+{
+ struct tslack_cgroup *tslack_cgroup;
+
+ tslack_cgroup = kmalloc(sizeof(*tslack_cgroup), GFP_KERNEL);
+ if (!tslack_cgroup)
+ return ERR_PTR(-ENOMEM);
+
+ if (cgroup->parent) {
+ struct tslack_cgroup *parent;
+
+ parent = cgroup_to_tslack(cgroup->parent);
+ tslack_cgroup->min_slack_ns = parent->min_slack_ns;
+ } else
+ tslack_cgroup->min_slack_ns = 0UL;
+
+ return &tslack_cgroup->css;
+}
+
+static void tslack_destroy(struct cgroup_subsys *tslack_cgroup,
+ struct cgroup *cgroup)
+{
+ kfree(cgroup_to_tslack(cgroup));
+}
+
+static u64 tslack_read_min(struct cgroup *cgroup, struct cftype *cft)
+{
+ return cgroup_to_tslack(cgroup)->min_slack_ns;
+}
+
+static int tslack_write_min(struct cgroup *cgroup, struct cftype *cft, u64 val)
+{
+ if (val > ULONG_MAX)
+ return -EINVAL;
+
+ cgroup_to_tslack(cgroup)->min_slack_ns = val;
+
+ return 0;
+}
+
+static u64 tslack_read_effective(struct cgroup *cgroup, struct cftype *cft)
+{
+ unsigned long min;
+
+ min = cgroup_to_tslack(cgroup)->min_slack_ns;
+ while (cgroup->parent) {
+ cgroup = cgroup->parent;
+ min = max(cgroup_to_tslack(cgroup)->min_slack_ns, min);
+ }
+
+ return min;
+}
+
+static struct cftype files[] = {
+ {
+ .name = "min_slack_ns",
+ .read_u64 = tslack_read_min,
+ .write_u64 = tslack_write_min,
+ },
+ {
+ .name = "effective_slack_ns",
+ .read_u64 = tslack_read_effective,
+ },
+};
+
+static int tslack_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",
+ .subsys_id = timer_slack_subsys_id,
+ .create = tslack_create,
+ .destroy = tslack_destroy,
+ .populate = tslack_populate,
+};
+
+unsigned long task_get_effective_timer_slack(struct task_struct *tsk)
+{
+ struct cgroup *cgroup;
+ unsigned long slack;
+
+ rcu_read_lock();
+ cgroup = task_cgroup(tsk, timer_slack_subsys.subsys_id);
+ slack = tslack_read_effective(cgroup, NULL);
+ rcu_read_unlock();
+
+ return max(tsk->timer_slack_ns, slack);
+}
--
1.7.4.1
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