[v2] memcg: Add memory.pressure_level events

Message ID 20130219044012.GA23356@lizard.sbx00618.mountca.wayport.net
State New
Headers show

Commit Message

Anton Vorontsov Feb. 19, 2013, 4:40 a.m.
With this patch userland applications that want to maintain the
interactivity/memory allocation cost can use the pressure level
notifications. The levels are defined like this:

The "low" level means that the system is reclaiming memory for new
allocations. Monitoring this reclaiming activity might be useful for
maintaining cache level. Upon notification, the program (typically
"Activity Manager") might analyze vmstat and act in advance (i.e.
prematurely shutdown unimportant services).

The "medium" level means that the system is experiencing medium memory
pressure, the system might be making swap, paging out active file caches,
etc. Upon this event applications may decide to further analyze
vmstat/zoneinfo/memcg or internal memory usage statistics and free any
resources that can be easily reconstructed or re-read from a disk.

The "critical" level means that the system is actively thrashing, it is
about to out of memory (OOM) or even the in-kernel OOM killer is on its
way to trigger. Applications should do whatever they can to help the
system. It might be too late to consult with vmstat or any other
statistics, so it's advisable to take an immediate action.

The events are propagated upward until the event is handled, i.e. the
events are not pass-through. Here is what this means: for example you have
three cgroups: A->B->C. Now you set up an event listener on cgroups A, B
and C, and suppose group C experiences some pressure. In this situation,
only group C will receive the notification, i.e. groups A and B will not
receive it. This is done to avoid excessive "broadcasting" of messages,
which disturbs the system and which is especially bad if we are low on
memory or thrashing. So, organize the cgroups wisely, or propagate the
events manually (or, ask us to implement the pass-through events,
explaining why would you need them.)

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
---

Hi all,

Many thanks for the previous reviews! In this revision:

- Addressed Glauber Costa's comments:
  o Use parent_mem_cgroup() instead of own parent function (also suggested
    by Kamezawa). This change also affected events distribution logic, so
    it became more like memory thresholds notifications, i.e. we deliver
    the event to the cgroup where the event originated, not to the parent
    cgroup; (This also addreses Kamezawa's remark regarding which cgroup
    receives which event.)
  o Register vmpressure cgroup file directly in memcontrol.c.

- Addressed Greg Thelen's comments:
  o Fixed bool/int inconsistency in the code;
  o Fixed nr_scanned accounting;
  o Don't use cryptic 's', 'r' abbreviations; get rid of confusing
    'window' argument.

- Addressed Kamezawa Hiroyuki's comments:
  o Moved declarations from mm/internal.h into linux/vmpressue.h;
  o Removed Kconfig symbol. Vmpressure is pretty lightweight (especially
    comparing to the memcg accounting). If it ever causes any measurable
    performance effect, we want to fix it, not paper it over with a
    Kconfig option. :-)
  o Removed read operation on pressure_level cgroup file. In apps, we only
    use notifications, we don't need the content of the file, so let's
    keep things simple for now. Plus this resolves questions like what
    should we return there when the system is not reclaiming;
  o Reworded documentation;
  o Improved comments for vmpressure_prio().


Old changelogs/submissions:
  v1: http://lkml.org/lkml/2013/2/10/140
  mempressure cgroup: http://lkml.org/lkml/2013/1/4/55

Thanks!

Anton

 Documentation/cgroups/memory.txt |  61 +++++++++-
 include/linux/vmpressure.h       |  47 ++++++++
 mm/Makefile                      |   2 +-
 mm/memcontrol.c                  |  28 +++++
 mm/vmpressure.c                  | 252 +++++++++++++++++++++++++++++++++++++++
 mm/vmscan.c                      |   8 ++
 6 files changed, 396 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/vmpressure.h
 create mode 100644 mm/vmpressure.c

Comments

Minchan Kim Feb. 20, 2013, 12:17 a.m. | #1
Hi Anton,

On Mon, Feb 18, 2013 at 08:40:12PM -0800, Anton Vorontsov wrote:
> With this patch userland applications that want to maintain the
> interactivity/memory allocation cost can use the pressure level
> notifications. The levels are defined like this:
> 
> The "low" level means that the system is reclaiming memory for new
> allocations. Monitoring this reclaiming activity might be useful for
> maintaining cache level. Upon notification, the program (typically
> "Activity Manager") might analyze vmstat and act in advance (i.e.
> prematurely shutdown unimportant services).
> 
> The "medium" level means that the system is experiencing medium memory
> pressure, the system might be making swap, paging out active file caches,
> etc. Upon this event applications may decide to further analyze
> vmstat/zoneinfo/memcg or internal memory usage statistics and free any
> resources that can be easily reconstructed or re-read from a disk.
> 
> The "critical" level means that the system is actively thrashing, it is
> about to out of memory (OOM) or even the in-kernel OOM killer is on its
> way to trigger. Applications should do whatever they can to help the
> system. It might be too late to consult with vmstat or any other
> statistics, so it's advisable to take an immediate action.
> 
> The events are propagated upward until the event is handled, i.e. the
> events are not pass-through. Here is what this means: for example you have
> three cgroups: A->B->C. Now you set up an event listener on cgroups A, B
> and C, and suppose group C experiences some pressure. In this situation,
> only group C will receive the notification, i.e. groups A and B will not
> receive it. This is done to avoid excessive "broadcasting" of messages,
> which disturbs the system and which is especially bad if we are low on
> memory or thrashing. So, organize the cgroups wisely, or propagate the
> events manually (or, ask us to implement the pass-through events,
> explaining why would you need them.)
> 
> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
> Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
> 
> Hi all,
> 
> Many thanks for the previous reviews! In this revision:
> 
> - Addressed Glauber Costa's comments:
>   o Use parent_mem_cgroup() instead of own parent function (also suggested
>     by Kamezawa). This change also affected events distribution logic, so
>     it became more like memory thresholds notifications, i.e. we deliver
>     the event to the cgroup where the event originated, not to the parent
>     cgroup; (This also addreses Kamezawa's remark regarding which cgroup
>     receives which event.)
>   o Register vmpressure cgroup file directly in memcontrol.c.
> 
> - Addressed Greg Thelen's comments:
>   o Fixed bool/int inconsistency in the code;
>   o Fixed nr_scanned accounting;
>   o Don't use cryptic 's', 'r' abbreviations; get rid of confusing
>     'window' argument.
> 
> - Addressed Kamezawa Hiroyuki's comments:
>   o Moved declarations from mm/internal.h into linux/vmpressue.h;
>   o Removed Kconfig symbol. Vmpressure is pretty lightweight (especially
>     comparing to the memcg accounting). If it ever causes any measurable
>     performance effect, we want to fix it, not paper it over with a
>     Kconfig option. :-)
>   o Removed read operation on pressure_level cgroup file. In apps, we only
>     use notifications, we don't need the content of the file, so let's
>     keep things simple for now. Plus this resolves questions like what
>     should we return there when the system is not reclaiming;
>   o Reworded documentation;
>   o Improved comments for vmpressure_prio().

Should we really enable memcg for just pressure notificaion in embedded side?
I didn't check the size(cgroup + memcg) and performance penalty but I don't want
to add unnecessary overhead if it is possible.
Do you have a plan to support it via global knob(ie, /proc/mempressure), NOT memcg?
Tejun Heo Feb. 20, 2013, 12:21 a.m. | #2
Hello,

On Tue, Feb 19, 2013 at 4:17 PM, Minchan Kim <minchan@kernel.org> wrote:
> Should we really enable memcg for just pressure notificaion in embedded side?
> I didn't check the size(cgroup + memcg) and performance penalty but I don't want
> to add unnecessary overhead if it is possible.
> Do you have a plan to support it via global knob(ie, /proc/mempressure), NOT memcg?

That should be handled by mempressure at the root cgroup. If that adds
significant amount of overhead code or memory-wise, we just need to
fix root cgroup handling in memcg. No reason to further complicate the
interface which already is pretty complex.

Thanks.
Anton Vorontsov Feb. 21, 2013, 11:04 p.m. | #3
On Tue, Feb 19, 2013 at 04:21:28PM -0800, Tejun Heo wrote:
> On Tue, Feb 19, 2013 at 4:17 PM, Minchan Kim <minchan@kernel.org> wrote:
> > Should we really enable memcg for just pressure notificaion in embedded side?
> > I didn't check the size(cgroup + memcg) and performance penalty but I don't want
> > to add unnecessary overhead if it is possible.
> > Do you have a plan to support it via global knob(ie, /proc/mempressure), NOT memcg?
> 
> That should be handled by mempressure at the root cgroup. If that adds
> significant amount of overhead code or memory-wise, we just need to
> fix root cgroup handling in memcg. No reason to further complicate the
> interface which already is pretty complex.

For what it worth, I agree here. Even if we decide to make another
interface to vmpressure (which, say, would not require memcg), then it is
better to keep the API the same: eventfd + control file. That way,
API/ABI-wise there will be no differnce between memcg and non-memcg
kernels, which is cool.

Thanks,
Anton
Minchan Kim Feb. 21, 2013, 11:56 p.m. | #4
Hi Anton,

On Thu, Feb 21, 2013 at 03:04:26PM -0800, Anton Vorontsov wrote:
> On Tue, Feb 19, 2013 at 04:21:28PM -0800, Tejun Heo wrote:
> > On Tue, Feb 19, 2013 at 4:17 PM, Minchan Kim <minchan@kernel.org> wrote:
> > > Should we really enable memcg for just pressure notificaion in embedded side?
> > > I didn't check the size(cgroup + memcg) and performance penalty but I don't want
> > > to add unnecessary overhead if it is possible.
> > > Do you have a plan to support it via global knob(ie, /proc/mempressure), NOT memcg?
> > 
> > That should be handled by mempressure at the root cgroup. If that adds
> > significant amount of overhead code or memory-wise, we just need to
> > fix root cgroup handling in memcg. No reason to further complicate the
> > interface which already is pretty complex.
> 
> For what it worth, I agree here. Even if we decide to make another
> interface to vmpressure (which, say, would not require memcg), then it is
> better to keep the API the same: eventfd + control file. That way,
> API/ABI-wise there will be no differnce between memcg and non-memcg
> kernels, which is cool.

I tend to agree Tejun's opinion POV maintain and I don't have a number
of memcg static/dynamic effect for embedded side so I don't want to argue now.
AFAIRC, Mel reported last year that memcg had rather no small runtime effect
and some memcg guys are trying to solve it. The memcg guy among Cced guys of
this thread could answer that more clearly.

I don't care whatever API looks like. Of course, keeping the API the same is
always good if we decide to need it. The my point is that you have a plan
to support? Why I have a question is that you said your goal is to replace
lowmemory killer but android don't have enabled CONFIG_MEMCG as you know well
so they should enable it for using just notifier? or they need another hack to
connect notifier to global thing?

What's the plan?

> 
> Thanks,
> Anton
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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Anton Vorontsov Feb. 22, 2013, 6:55 a.m. | #5
On Fri, Feb 22, 2013 at 08:56:08AM +0900, Minchan Kim wrote:
> [...] The my point is that you have a plan to support? Why I have a
> question is that you said your goal is to replace lowmemory killer

In short: yes, of course, if the non-memcg interface will be in demand.

> but android don't have enabled CONFIG_MEMCG as you know well
> so they should enable it for using just notifier? or they need another hack to
> connect notifier to global thing?

A hack is not an option for me. :-) My final goal is to switch Android to
use the notifier without need for hacks/external patches or
drivers/staging.

But my current goal is to make the most generic case work, and do this in
the most correct way. That is, vmpressure + MEMCG. Once I accomplish this,
I can then think of any niche needs (such as Android).

There will be two possibilities for Android:

1. Obviously, turn on CONFIG_MEMCG. We need to measure its effect on real
   devices, and see if it makes sense. (Plus, maybe there are other uses
   for MEMCG on Android?)

or

2. Implement /sys/fs/cgroups/memory/memory.pressure_level interface
   without MEMCG. Doing this will be really easy as we'll already have
   vmpressure() core, and Android has CROUPS=y. But I do expect some
   discussion like 'why don't you fix memcg instead?'. We'll have to
   answer this question by looking back at '1.'

Also note that cgroups vmpressure notifiers were tried by QEMU folks, and
it seemed to be useful:

   http://lists.gnu.org/archive/html/qemu-devel/2012-12/msg02821.html 

So, nowadays it is not only about Android. Some time ago I also got an
email from Orna Agmon Ben-Yehuda, who suggested to use vmpressure stuff
with 'memcached' (but I didn't find time to actually try it, so far. :(
Thanks for the email, btw!).

So it is useful with or without MEMCG, and if we will really need to
support vmpressure without MEMCG, I will have to implement the support in
addition to MEMCG case, yes.

Thanks,

Anton
Minchan Kim Feb. 22, 2013, 7:26 a.m. | #6
On Thu, Feb 21, 2013 at 10:55:52PM -0800, Anton Vorontsov wrote:
> On Fri, Feb 22, 2013 at 08:56:08AM +0900, Minchan Kim wrote:
> > [...] The my point is that you have a plan to support? Why I have a
> > question is that you said your goal is to replace lowmemory killer
> 
> In short: yes, of course, if the non-memcg interface will be in demand.
> 
> > but android don't have enabled CONFIG_MEMCG as you know well
> > so they should enable it for using just notifier? or they need another hack to
> > connect notifier to global thing?
> 
> A hack is not an option for me. :-) My final goal is to switch Android to
> use the notifier without need for hacks/external patches or
> drivers/staging.
> 
> But my current goal is to make the most generic case work, and do this in
> the most correct way. That is, vmpressure + MEMCG. Once I accomplish this,
> I can then think of any niche needs (such as Android).
> 
> There will be two possibilities for Android:
> 
> 1. Obviously, turn on CONFIG_MEMCG. We need to measure its effect on real
>    devices, and see if it makes sense. (Plus, maybe there are other uses
>    for MEMCG on Android?)

I'd like to see this one.

> 
> or
> 
> 2. Implement /sys/fs/cgroups/memory/memory.pressure_level interface
>    without MEMCG. Doing this will be really easy as we'll already have
>    vmpressure() core, and Android has CROUPS=y. But I do expect some
>    discussion like 'why don't you fix memcg instead?'. We'll have to
>    answer this question by looking back at '1.'

Of course.

> 
> Also note that cgroups vmpressure notifiers were tried by QEMU folks, and
> it seemed to be useful:
> 
>    http://lists.gnu.org/archive/html/qemu-devel/2012-12/msg02821.html 

I saw that.

> 
> So, nowadays it is not only about Android. Some time ago I also got an
> email from Orna Agmon Ben-Yehuda, who suggested to use vmpressure stuff
> with 'memcached' (but I didn't find time to actually try it, so far. :(
> Thanks for the email, btw!).

I also got received email from another people in embedded side about
memory notifier which I worked long time ago and I used to introduce
your work to them instead of my old solution.
It seems they don't use Android and has very small RAM so they want
to handle memory very efficiently. For such purpose, I hope vmpressure
become tiny and can support even NOMMU system.

> 
> So it is useful with or without MEMCG, and if we will really need to
> support vmpressure without MEMCG, I will have to implement the support in
> addition to MEMCG case, yes.

Thanks for your clarification.

> 
> Thanks,
> 
> Anton
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Patch hide | download patch | download mbox

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index addb1f1..0c004de 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -40,6 +40,7 @@  Features:
  - soft limit
  - moving (recharging) account at moving a task is selectable.
  - usage threshold notifier
+ - memory pressure notifier
  - oom-killer disable knob and oom-notifier
  - Root cgroup has no limit controls.
 
@@ -65,6 +66,7 @@  Brief summary of control files.
  memory.stat			 # show various statistics
  memory.use_hierarchy		 # set/show hierarchical account enabled
  memory.force_empty		 # trigger forced move charge to parent
+ memory.pressure_level		 # set memory pressure notifications
  memory.swappiness		 # set/show swappiness parameter of vmscan
 				 (See sysctl's vm.swappiness)
  memory.move_charge_at_immigrate # set/show controls of moving charges
@@ -778,7 +780,64 @@  At reading, current status of OOM is shown.
 	under_oom	 0 or 1 (if 1, the memory cgroup is under OOM, tasks may
 				 be stopped.)
 
-11. TODO
+11. Memory Pressure
+
+The pressure level notifications can be used to monitor the memory
+allocation cost; based on the pressure, applications can implement
+different strategies of managing their memory resources. The pressure
+levels are defined as following:
+
+The "low" level means that the system is reclaiming memory for new
+allocations. Monitoring this reclaiming activity might be useful for
+maintaining cache level. Upon notification, the program (typically
+"Activity Manager") might analyze vmstat and act in advance (i.e.
+prematurely shutdown unimportant services).
+
+The "medium" level means that the system is experiencing medium memory
+pressure, the system might be making swap, paging out active file caches,
+etc. Upon this event applications may decide to further analyze
+vmstat/zoneinfo/memcg or internal memory usage statistics and free any
+resources that can be easily reconstructed or re-read from a disk.
+
+The "critical" level means that the system is actively thrashing, it is
+about to out of memory (OOM) or even the in-kernel OOM killer is on its
+way to trigger. Applications should do whatever they can to help the
+system. It might be too late to consult with vmstat or any other
+statistics, so it's advisable to take an immediate action.
+
+The events are propagated upward until the event is handled, i.e. the
+events are not pass-through. Here is what this means: for example you have
+three cgroups: A->B->C. Now you set up an event listener on cgroups A, B
+and C, and suppose group C experiences some pressure. In this situation,
+only group C will receive the notification, i.e. groups A and B will not
+receive it. This is done to avoid excessive "broadcasting" of messages,
+which disturbs the system and which is especially bad if we are low on
+memory or thrashing. So, organize the cgroups wisely, or propagate the
+events manually (or, ask us to implement the pass-through events,
+explaining why would you need them.)
+
+The file memory.pressure_level is only used to setup an eventfd,
+read/write operations are no implemented.
+
+Test:
+
+   Here is a small script example that makes a new cgroup, sets up a
+   memory limit, sets up a notification in the cgroup and then makes child
+   cgroup experience a critical pressure:
+
+   # cd /sys/fs/cgroup/memory/
+   # mkdir foo
+   # cd foo
+   # cgroup_event_listener memory.pressure_level low &
+   # echo 8000000 > memory.limit_in_bytes
+   # echo 8000000 > memory.memsw.limit_in_bytes
+   # echo $$ > tasks
+   # dd if=/dev/zero | read x
+
+   (Expect a bunch of notifications, and eventually, the oom-killer will
+   trigger.)
+
+12. TODO
 
 1. Add support for accounting huge pages (as a separate controller)
 2. Make per-cgroup scanner reclaim not-shared pages first
diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h
new file mode 100644
index 0000000..fa84783
--- /dev/null
+++ b/include/linux/vmpressure.h
@@ -0,0 +1,47 @@ 
+#ifndef __LINUX_VMPRESSURE_H
+#define __LINUX_VMPRESSURE_H
+
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/gfp.h>
+#include <linux/types.h>
+#include <linux/cgroup.h>
+
+struct vmpressure {
+	unsigned int scanned;
+	unsigned int reclaimed;
+	/* The lock is used to keep the scanned/reclaimed above in sync. */
+	struct mutex sr_lock;
+
+	struct list_head events;
+	/* Have to grab the lock on events traversal or modifications. */
+	struct mutex events_lock;
+
+	struct work_struct work;
+};
+
+struct mem_cgroup;
+
+#ifdef CONFIG_MEMCG
+extern void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
+		       unsigned long scanned, unsigned long reclaimed);
+extern void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio);
+#else
+static inline void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
+			      unsigned long scanned, unsigned long reclaimed) {}
+static inline void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg,
+				   int prio) {}
+#endif /* CONFIG_MEMCG */
+
+extern void vmpressure_init(struct vmpressure *vmpr);
+extern struct vmpressure *memcg_to_vmpr(struct mem_cgroup *memcg);
+extern struct cgroup_subsys_state *vmpr_to_css(struct vmpressure *vmpr);
+extern struct vmpressure *css_to_vmpr(struct cgroup_subsys_state *css);
+extern int vmpressure_register_event(struct cgroup *cg, struct cftype *cft,
+				     struct eventfd_ctx *eventfd,
+				     const char *args);
+extern void vmpressure_unregister_event(struct cgroup *cg, struct cftype *cft,
+					struct eventfd_ctx *eventfd);
+
+#endif /* __LINUX_VMPRESSURE_H */
diff --git a/mm/Makefile b/mm/Makefile
index 3a46287..72c5acb 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -50,7 +50,7 @@  obj-$(CONFIG_FS_XIP) += filemap_xip.o
 obj-$(CONFIG_MIGRATION) += migrate.o
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o
-obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o
+obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o vmpressure.o
 obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
 obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 25ac5f4..b41727b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -49,6 +49,7 @@ 
 #include <linux/fs.h>
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
+#include <linux/vmpressure.h>
 #include <linux/mm_inline.h>
 #include <linux/page_cgroup.h>
 #include <linux/cpu.h>
@@ -370,6 +371,9 @@  struct mem_cgroup {
 	atomic_t	numainfo_events;
 	atomic_t	numainfo_updating;
 #endif
+
+	struct vmpressure vmpr;
+
 	/*
 	 * Per cgroup active and inactive list, similar to the
 	 * per zone LRU lists.
@@ -570,6 +574,24 @@  struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
 	return container_of(s, struct mem_cgroup, css);
 }
 
+/* Some nice accessors for the vmpressure. */
+struct vmpressure *memcg_to_vmpr(struct mem_cgroup *memcg)
+{
+	if (!memcg)
+		memcg = root_mem_cgroup;
+	return &memcg->vmpr;
+}
+
+struct cgroup_subsys_state *vmpr_to_css(struct vmpressure *vmpr)
+{
+	return &container_of(vmpr, struct mem_cgroup, vmpr)->css;
+}
+
+struct vmpressure *css_to_vmpr(struct cgroup_subsys_state *css)
+{
+	return &mem_cgroup_from_css(css)->vmpr;
+}
+
 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 {
 	return (memcg == root_mem_cgroup);
@@ -6000,6 +6022,11 @@  static struct cftype mem_cgroup_files[] = {
 		.unregister_event = mem_cgroup_oom_unregister_event,
 		.private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
 	},
+	{
+		.name = "pressure_level",
+		.register_event = vmpressure_register_event,
+		.unregister_event = vmpressure_unregister_event,
+	},
 #ifdef CONFIG_NUMA
 	{
 		.name = "numa_stat",
@@ -6291,6 +6318,7 @@  mem_cgroup_css_alloc(struct cgroup *cont)
 	memcg->move_charge_at_immigrate = 0;
 	mutex_init(&memcg->thresholds_lock);
 	spin_lock_init(&memcg->move_lock);
+	vmpressure_init(&memcg->vmpr);
 
 	return &memcg->css;
 
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
new file mode 100644
index 0000000..ae0ff8e
--- /dev/null
+++ b/mm/vmpressure.c
@@ -0,0 +1,252 @@ 
+/*
+ * Linux VM pressure
+ *
+ * Copyright 2012 Linaro Ltd.
+ *		  Anton Vorontsov <anton.vorontsov@linaro.org>
+ *
+ * Based on ideas from Andrew Morton, David Rientjes, KOSAKI Motohiro,
+ * Leonid Moiseichuk, Mel Gorman, Minchan Kim and Pekka Enberg.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+
+#include <linux/cgroup.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/vmstat.h>
+#include <linux/eventfd.h>
+#include <linux/swap.h>
+#include <linux/printk.h>
+#include <linux/vmpressure.h>
+
+/*
+ * The window size is the number of scanned pages before we try to analyze
+ * the scanned/reclaimed ratio (or difference).
+ *
+ * It is used as a rate-limit tunable for the "low" level notification,
+ * and for averaging medium/critical levels. Using small window sizes can
+ * cause lot of false positives, but too big window size will delay the
+ * notifications.
+ *
+ * TODO: Make the window size depend on machine size, as we do for vmstat
+ * thresholds.
+ */
+static const unsigned int vmpressure_win = SWAP_CLUSTER_MAX * 16;
+static const unsigned int vmpressure_level_med = 60;
+static const unsigned int vmpressure_level_critical = 95;
+static const unsigned int vmpressure_level_critical_prio = 3;
+
+enum vmpressure_levels {
+	VMPRESSURE_LOW = 0,
+	VMPRESSURE_MEDIUM,
+	VMPRESSURE_CRITICAL,
+	VMPRESSURE_NUM_LEVELS,
+};
+
+static const char *vmpressure_str_levels[] = {
+	[VMPRESSURE_LOW] = "low",
+	[VMPRESSURE_MEDIUM] = "medium",
+	[VMPRESSURE_CRITICAL] = "critical",
+};
+
+static enum vmpressure_levels vmpressure_level(unsigned int pressure)
+{
+	if (pressure >= vmpressure_level_critical)
+		return VMPRESSURE_CRITICAL;
+	else if (pressure >= vmpressure_level_med)
+		return VMPRESSURE_MEDIUM;
+	return VMPRESSURE_LOW;
+}
+
+static enum vmpressure_levels vmpressure_calc_level(unsigned int scanned,
+						    unsigned int reclaimed)
+{
+	unsigned long scale = scanned + reclaimed;
+	unsigned long pressure;
+
+	if (!scanned)
+		return VMPRESSURE_LOW;
+
+	/*
+	 * We calculate the ratio (in percents) of how many pages were
+	 * scanned vs. reclaimed in a given time frame (window). Note that
+	 * time is in VM reclaimer's "ticks", i.e. number of pages
+	 * scanned. This makes it possible to set desired reaction time
+	 * and serves as a ratelimit.
+	 */
+	pressure = scale - (reclaimed * scale / scanned);
+	pressure = pressure * 100 / scale;
+
+	pr_debug("%s: %3lu  (s: %6u  r: %6u)\n", __func__, pressure,
+		 scanned, reclaimed);
+
+	return vmpressure_level(pressure);
+}
+
+void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
+		unsigned long scanned, unsigned long reclaimed)
+{
+	struct vmpressure *vmpr = memcg_to_vmpr(memcg);
+
+	/*
+	 * So far we are only interested application memory, or, in case
+	 * of low pressure, in FS/IO memory reclaim. We are also
+	 * interested indirect reclaim (kswapd sets sc->gfp_mask to
+	 * GFP_KERNEL).
+	 */
+	if (!(gfp & (__GFP_HIGHMEM | __GFP_MOVABLE | __GFP_IO | __GFP_FS)))
+		return;
+
+	if (!scanned)
+		return;
+
+	mutex_lock(&vmpr->sr_lock);
+	vmpr->scanned += scanned;
+	vmpr->reclaimed += reclaimed;
+	mutex_unlock(&vmpr->sr_lock);
+
+	if (scanned < vmpressure_win || work_pending(&vmpr->work))
+		return;
+	schedule_work(&vmpr->work);
+}
+
+void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio)
+{
+	if (prio > vmpressure_level_critical_prio)
+		return;
+
+	/*
+	 * OK, the prio is below the threshold, updating vmpressure
+	 * information before diving into long shrinking of long range
+	 * vmscan.
+	 */
+	vmpressure(gfp, memcg, vmpressure_win, 0);
+}
+
+static struct vmpressure *wk_to_vmpr(struct work_struct *wk)
+{
+	return container_of(wk, struct vmpressure, work);
+}
+
+static struct vmpressure *cg_to_vmpr(struct cgroup *cg)
+{
+	return css_to_vmpr(cgroup_subsys_state(cg, mem_cgroup_subsys_id));
+}
+
+struct vmpressure_event {
+	struct eventfd_ctx *efd;
+	enum vmpressure_levels level;
+	struct list_head node;
+};
+
+static bool vmpressure_event(struct vmpressure *vmpr,
+			     unsigned long scanned, unsigned long reclaimed)
+{
+	struct vmpressure_event *ev;
+	int level = vmpressure_calc_level(scanned, reclaimed);
+	bool signalled = false;
+
+	mutex_lock(&vmpr->events_lock);
+
+	list_for_each_entry(ev, &vmpr->events, node) {
+		if (level >= ev->level) {
+			eventfd_signal(ev->efd, 1);
+			signalled = true;
+		}
+	}
+
+	mutex_unlock(&vmpr->events_lock);
+
+	return signalled;
+}
+
+static struct vmpressure *vmpressure_parent(struct vmpressure *vmpr)
+{
+	struct cgroup *cg = vmpr_to_css(vmpr)->cgroup;
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cg);
+
+	memcg = parent_mem_cgroup(memcg);
+	if (!memcg)
+		return NULL;
+	return memcg_to_vmpr(memcg);
+}
+
+static void vmpressure_wk_fn(struct work_struct *wk)
+{
+	struct vmpressure *vmpr = wk_to_vmpr(wk);
+	unsigned long s;
+	unsigned long r;
+
+	mutex_lock(&vmpr->sr_lock);
+	s = vmpr->scanned;
+	r = vmpr->reclaimed;
+	vmpr->scanned = 0;
+	vmpr->reclaimed = 0;
+	mutex_unlock(&vmpr->sr_lock);
+
+	do {
+		if (vmpressure_event(vmpr, s, r))
+			break;
+		/*
+		 * If not handled, propagate the event upward into the
+		 * hierarchy.
+		 */
+	} while ((vmpr = vmpressure_parent(vmpr)));
+}
+
+int vmpressure_register_event(struct cgroup *cg, struct cftype *cft,
+			      struct eventfd_ctx *eventfd, const char *args)
+{
+	struct vmpressure *vmpr = cg_to_vmpr(cg);
+	struct vmpressure_event *ev;
+	int lvl;
+
+	for (lvl = 0; lvl < VMPRESSURE_NUM_LEVELS; lvl++) {
+		if (!strcmp(vmpressure_str_levels[lvl], args))
+			break;
+	}
+
+	if (lvl >= VMPRESSURE_NUM_LEVELS)
+		return -EINVAL;
+
+	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->efd = eventfd;
+	ev->level = lvl;
+
+	mutex_lock(&vmpr->events_lock);
+	list_add(&ev->node, &vmpr->events);
+	mutex_unlock(&vmpr->events_lock);
+
+	return 0;
+}
+
+void vmpressure_unregister_event(struct cgroup *cg, struct cftype *cft,
+				 struct eventfd_ctx *eventfd)
+{
+	struct vmpressure *vmpr = cg_to_vmpr(cg);
+	struct vmpressure_event *ev;
+
+	mutex_lock(&vmpr->events_lock);
+	list_for_each_entry(ev, &vmpr->events, node) {
+		if (ev->efd != eventfd)
+			continue;
+		list_del(&ev->node);
+		kfree(ev);
+		break;
+	}
+	mutex_unlock(&vmpr->events_lock);
+}
+
+void vmpressure_init(struct vmpressure *vmpr)
+{
+	mutex_init(&vmpr->sr_lock);
+	mutex_init(&vmpr->events_lock);
+	INIT_LIST_HEAD(&vmpr->events);
+	INIT_WORK(&vmpr->work, vmpressure_wk_fn);
+}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 88c5fed..9530777 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -19,6 +19,7 @@ 
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/vmpressure.h>
 #include <linux/vmstat.h>
 #include <linux/file.h>
 #include <linux/writeback.h>
@@ -1982,6 +1983,11 @@  static void shrink_zone(struct zone *zone, struct scan_control *sc)
 			}
 			memcg = mem_cgroup_iter(root, memcg, &reclaim);
 		} while (memcg);
+
+		vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
+			   sc->nr_scanned - nr_scanned,
+			   sc->nr_reclaimed - nr_reclaimed);
+
 	} while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
 					 sc->nr_scanned - nr_scanned, sc));
 }
@@ -2167,6 +2173,8 @@  static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 		count_vm_event(ALLOCSTALL);
 
 	do {
+		vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
+				sc->priority);
 		sc->nr_scanned = 0;
 		aborted_reclaim = shrink_zones(zonelist, sc);