[RFC][PATCH] memcg documentaion update

[RFC][PATCH] memcg documentaion update

[KAMEZAWA Hiroyuki]

At reading Documentation/cgroup/memory.txt, I felt

 - old
 - hard to find it's supported what I want to do

Hmm..maybe some rewrite will be necessary.

==
Documentation update. We have too much files now....

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 Documentation/cgroups/memory.txt |   48 ++++++++++++++++++++++++++++++---------
 1 file changed, 38 insertions(+), 10 deletions(-)

Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
===================================================================
--- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
+++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
@@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
 to as the memory controller in this document. Do not confuse memory controller
 used here with the memory controller that is used in hardware.
 
-Salient features
-
-a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
-   Swap Cache memory pages.
-b. The infrastructure allows easy addition of other types of memory to control
-c. Provides *zero overhead* for non memory controller users
-d. Provides a double LRU: global memory pressure causes reclaim from the
-   global LRU; a cgroup on hitting a limit, reclaims from the per
-   cgroup LRU
-
 Benefits and Purpose of the memory controller
 
 The memory controller isolates the memory behaviour of a group of tasks
@@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
 e. There are several other use cases, find one or use the controller just
    for fun (to learn and hack on the VM subsystem).
 
+Current Status: linux-2.6.34-mmotom(2010/March)
+
+Features:
+ - accounting anonymous pages, file caches, swap caches usage and limit them.
+ - private LRU and reclaim routine. (system's global LRU and private LRU
+   work independently from each other)
+ - optionaly, memory+swap usage
+ - hierarchical accounting
+ - softlimit
+ - moving(recharging) account at moving a task
+ - usage threshold notifier
+ - oom-killer disable and oom-notifier
+ - Root cgroup has no limit controls.
+
+ Kernel memory and Hugepages are not under control yet. We just manage
+ pages on LRU. To add more controls, we have to take care of performance.
+
+Brief summary of control files.
+
+ tasks				# attach a task(thread)
+ cgroup.procs			# attach a process(all threads under it)
+ cgroup.event_control		# an interface for event_fd()
+ memory.usage_in_bytes		# show current memory(RSS+Cache) usage.
+ memory.memsw.usage_in_bytes	# show current memory+Swap usage.
+ memory.limit_in_bytes		# set/show limit of memory usage
+ memory.memsw.limit_in_bytes	# set/show limit of memory+Swap usage.
+ memory.failcnt			# show the number of memory usage hit limits.
+ memory.memsw.failcnt		# show the number of memory+Swap hit limits.
+ memory.max_usage_in_bytes	# show max memory usage recorded.
+ memory.memsw.usage_in_bytes	# show max memory+Swap usage recorded.
+ memory.stat			# show various statistics.
+ memory.use_hierarchy		# set/show hierarchical account enabled.
+ memory.force_empty		# trigger forced move charge to parent.
+ memory.swappiness		# set/show swappiness parameter of vmscan
+ 				  (See sysctl's vm.swappiness)
+ memory.move_charge_at_immigrate# set/show controls of moving charges
+ memory.oom_control		# set/show oom controls.
+
 1. History
 
 The memory controller has a long history. A request for comments for the memory

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Re: [RFC][PATCH] memcg documentaion update

[Daisuke Nishimura]

On Mon, 29 Mar 2010 15:42:45 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> At reading Documentation/cgroup/memory.txt, I felt
> 
>  - old
>  - hard to find it's supported what I want to do
> 
> Hmm..maybe some rewrite will be necessary.
> 
I agree.

> ==
> Documentation update. We have too much files now....
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  Documentation/cgroups/memory.txt |   48 ++++++++++++++++++++++++++++++---------
>  1 file changed, 38 insertions(+), 10 deletions(-)
> 
> Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
>  to as the memory controller in this document. Do not confuse memory controller
>  used here with the memory controller that is used in hardware.
>  
> -Salient features
> -
> -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
> -   Swap Cache memory pages.
> -b. The infrastructure allows easy addition of other types of memory to control
> -c. Provides *zero overhead* for non memory controller users
> -d. Provides a double LRU: global memory pressure causes reclaim from the
> -   global LRU; a cgroup on hitting a limit, reclaims from the per
> -   cgroup LRU
> -
>  Benefits and Purpose of the memory controller
>  
>  The memory controller isolates the memory behaviour of a group of tasks
> @@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
>  e. There are several other use cases, find one or use the controller just
>     for fun (to learn and hack on the VM subsystem).
>  
> +Current Status: linux-2.6.34-mmotom(2010/March)
> +
> +Features:
> + - accounting anonymous pages, file caches, swap caches usage and limit them.
> + - private LRU and reclaim routine. (system's global LRU and private LRU
> +   work independently from each other)
> + - optionaly, memory+swap usage
> + - hierarchical accounting
> + - softlimit
> + - moving(recharging) account at moving a task
> + - usage threshold notifier
> + - oom-killer disable and oom-notifier
> + - Root cgroup has no limit controls.
> +
> + Kernel memory and Hugepages are not under control yet. We just manage
> + pages on LRU. To add more controls, we have to take care of performance.
> +
> +Brief summary of control files.
> +
> + tasks				# attach a task(thread)
> + cgroup.procs			# attach a process(all threads under it)
> + cgroup.event_control		# an interface for event_fd()
> + memory.usage_in_bytes		# show current memory(RSS+Cache) usage.
> + memory.memsw.usage_in_bytes	# show current memory+Swap usage.
> + memory.limit_in_bytes		# set/show limit of memory usage
> + memory.memsw.limit_in_bytes	# set/show limit of memory+Swap usage.
> + memory.failcnt			# show the number of memory usage hit limits.
> + memory.memsw.failcnt		# show the number of memory+Swap hit limits.
> + memory.max_usage_in_bytes	# show max memory usage recorded.
> + memory.memsw.usage_in_bytes	# show max memory+Swap usage recorded.
> + memory.stat			# show various statistics.
> + memory.use_hierarchy		# set/show hierarchical account enabled.
> + memory.force_empty		# trigger forced move charge to parent.
> + memory.swappiness		# set/show swappiness parameter of vmscan
> + 				  (See sysctl's vm.swappiness)
> + memory.move_charge_at_immigrate# set/show controls of moving charges
> + memory.oom_control		# set/show oom controls.
> +
These changes would be very useful to let users know memcg's features at a glance.

>  1. History
>  
>  The memory controller has a long history. A request for comments for the memory
> 

BTW, I think it might be better to update 5.2(stat file) too.
"mapped_file" and "swap"(sorry, my fault) aren't listed there.


Thanks,
Daisuke Nishimura.

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Re: [RFC][PATCH] memcg documentaion update

[KAMEZAWA Hiroyuki]

On Tue, 30 Mar 2010 09:13:03 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Mon, 29 Mar 2010 15:42:45 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > At reading Documentation/cgroup/memory.txt, I felt
> > 
> >  - old
> >  - hard to find it's supported what I want to do
> > 
> > Hmm..maybe some rewrite will be necessary.
> > 
> I agree.
> 
> > ==
> > Documentation update. We have too much files now....
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  Documentation/cgroups/memory.txt |   48 ++++++++++++++++++++++++++++++---------
> >  1 file changed, 38 insertions(+), 10 deletions(-)
> > 
> > Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> > ===================================================================
> > --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> > +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> > @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
> >  to as the memory controller in this document. Do not confuse memory controller
> >  used here with the memory controller that is used in hardware.
> >  
> > -Salient features
> > -
> > -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
> > -   Swap Cache memory pages.
> > -b. The infrastructure allows easy addition of other types of memory to control
> > -c. Provides *zero overhead* for non memory controller users
> > -d. Provides a double LRU: global memory pressure causes reclaim from the
> > -   global LRU; a cgroup on hitting a limit, reclaims from the per
> > -   cgroup LRU
> > -
> >  Benefits and Purpose of the memory controller
> >  
> >  The memory controller isolates the memory behaviour of a group of tasks
> > @@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
> >  e. There are several other use cases, find one or use the controller just
> >     for fun (to learn and hack on the VM subsystem).
> >  
> > +Current Status: linux-2.6.34-mmotom(2010/March)
> > +
> > +Features:
> > + - accounting anonymous pages, file caches, swap caches usage and limit them.
> > + - private LRU and reclaim routine. (system's global LRU and private LRU
> > +   work independently from each other)
> > + - optionaly, memory+swap usage
> > + - hierarchical accounting
> > + - softlimit
> > + - moving(recharging) account at moving a task
> > + - usage threshold notifier
> > + - oom-killer disable and oom-notifier
> > + - Root cgroup has no limit controls.
> > +
> > + Kernel memory and Hugepages are not under control yet. We just manage
> > + pages on LRU. To add more controls, we have to take care of performance.
> > +
> > +Brief summary of control files.
> > +
> > + tasks				# attach a task(thread)
> > + cgroup.procs			# attach a process(all threads under it)
> > + cgroup.event_control		# an interface for event_fd()
> > + memory.usage_in_bytes		# show current memory(RSS+Cache) usage.
> > + memory.memsw.usage_in_bytes	# show current memory+Swap usage.
> > + memory.limit_in_bytes		# set/show limit of memory usage
> > + memory.memsw.limit_in_bytes	# set/show limit of memory+Swap usage.
> > + memory.failcnt			# show the number of memory usage hit limits.
> > + memory.memsw.failcnt		# show the number of memory+Swap hit limits.
> > + memory.max_usage_in_bytes	# show max memory usage recorded.
> > + memory.memsw.usage_in_bytes	# show max memory+Swap usage recorded.
> > + memory.stat			# show various statistics.
> > + memory.use_hierarchy		# set/show hierarchical account enabled.
> > + memory.force_empty		# trigger forced move charge to parent.
> > + memory.swappiness		# set/show swappiness parameter of vmscan
> > + 				  (See sysctl's vm.swappiness)
> > + memory.move_charge_at_immigrate# set/show controls of moving charges
> > + memory.oom_control		# set/show oom controls.
> > +
> These changes would be very useful to let users know memcg's features at a glance.
> 
> >  1. History
> >  
> >  The memory controller has a long history. A request for comments for the memory
> > 
> 
> BTW, I think it might be better to update 5.2(stat file) too.
> "mapped_file" and "swap"(sorry, my fault) aren't listed there.
> 
Sure, I'll add.

Thanks,
-Kame


> 
> Thanks,
> Daisuke Nishimura.
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
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Re: [RFC][PATCH] memcg documentaion update

[KAMEZAWA Hiroyuki]

On Mon, 29 Mar 2010 17:47:24 -0700
Greg Thelen <gthelen@google.com> wrote:

> On Sun, Mar 28, 2010 at 11:42 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> >
> > At reading Documentation/cgroup/memory.txt, I felt
> >
> > A - old
> > A - hard to find it's supported what I want to do
> >
> > Hmm..maybe some rewrite will be necessary.
> >
> > ==
> > Documentation update. We have too much files now....
> >
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> > A Documentation/cgroups/memory.txt | A  48 ++++++++++++++++++++++++++++++---------
> > A 1 file changed, 38 insertions(+), 10 deletions(-)
> >
> > Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> > ===================================================================
> > --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> > +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> > @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
> > A to as the memory controller in this document. Do not confuse memory controller
> > A used here with the memory controller that is used in hardware.
> >
> > -Salient features
> > -
> > -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
> > - A  Swap Cache memory pages.
> > -b. The infrastructure allows easy addition of other types of memory to control
> > -c. Provides *zero overhead* for non memory controller users
> > -d. Provides a double LRU: global memory pressure causes reclaim from the
> > - A  global LRU; a cgroup on hitting a limit, reclaims from the per
> > - A  cgroup LRU
> > -
> > A Benefits and Purpose of the memory controller
> >
> > A The memory controller isolates the memory behaviour of a group of tasks
> > @@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
> > A e. There are several other use cases, find one or use the controller just
> > A  A for fun (to learn and hack on the VM subsystem).
> >
> > +Current Status: linux-2.6.34-mmotom(2010/March)
> > +
> > +Features:
> > + - accounting anonymous pages, file caches, swap caches usage and limit them.
> > + - private LRU and reclaim routine. (system's global LRU and private LRU
> > + A  work independently from each other)
> > + - optionaly, memory+swap usage
> > + - hierarchical accounting
> > + - softlimit
> > + - moving(recharging) account at moving a task
> > + - usage threshold notifier
> > + - oom-killer disable and oom-notifier
> > + - Root cgroup has no limit controls.
> > +
> > + Kernel memory and Hugepages are not under control yet. We just manage
> > + pages on LRU. To add more controls, we have to take care of performance.
> > +
> > +Brief summary of control files.
> > +
> > + tasks A  A  A  A  A  A  A  A  A  A  A  A  # attach a task(thread)
> > + cgroup.procs A  A  A  A  A  A  A  A  A # attach a process(all threads under it)
> > + cgroup.event_control A  A  A  A  A # an interface for event_fd()
> > + memory.usage_in_bytes A  A  A  A  # show current memory(RSS+Cache) usage.
> > + memory.memsw.usage_in_bytes A  # show current memory+Swap usage.
> > + memory.limit_in_bytes A  A  A  A  # set/show limit of memory usage
> > + memory.memsw.limit_in_bytes A  # set/show limit of memory+Swap usage.
> > + memory.failcnt A  A  A  A  A  A  A  A  A  A  A  A # show the number of memory usage hit limits.
> > + memory.memsw.failcnt A  A  A  A  A # show the number of memory+Swap hit limits.
> > + memory.max_usage_in_bytes A  A  # show max memory usage recorded.
> > + memory.memsw.usage_in_bytes A  # show max memory+Swap usage recorded.
> > + memory.stat A  A  A  A  A  A  A  A  A  # show various statistics.
> > + memory.use_hierarchy A  A  A  A  A # set/show hierarchical account enabled.
> > + memory.force_empty A  A  A  A  A  A # trigger forced move charge to parent.
> > + memory.swappiness A  A  A  A  A  A  # set/show swappiness parameter of vmscan
> > + A  A  A  A  A  A  A  A  A  A  A  A  A  A  A  A  (See sysctl's vm.swappiness)
> > + memory.move_charge_at_immigrate# set/show controls of moving charges
> > + memory.oom_control A  A  A  A  A  A # set/show oom controls.
> > +
> > A 1. History
> >
> > A The memory controller has a long history. A request for comments for the memory
> >
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@kvack.org. A 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>
> 
> Two comments:
> 1. Should we also include a description of the
> memory.soft_limit_in_bytes control file in the "Brief summary"
> section?
> 
Oh, it's just a mistake. I'll fix.

> 2. the subject of this thread misspelled "documentation
> (s/documentaion/documentation/).  Not a problem, but you might want to
> fix it for eventually patch submission.
> 
I'll use spell checker in the next post.

Thanks,
-Kame


> --
> Greg
> 

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Re: [RFC][PATCH] memcg documentaion update

[Greg Thelen]

On Sun, Mar 28, 2010 at 11:42 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> At reading Documentation/cgroup/memory.txt, I felt
>
>  - old
>  - hard to find it's supported what I want to do
>
> Hmm..maybe some rewrite will be necessary.
>
> ==
> Documentation update. We have too much files now....
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  Documentation/cgroups/memory.txt |   48 ++++++++++++++++++++++++++++++---------
>  1 file changed, 38 insertions(+), 10 deletions(-)
>
> Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
>  to as the memory controller in this document. Do not confuse memory controller
>  used here with the memory controller that is used in hardware.
>
> -Salient features
> -
> -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
> -   Swap Cache memory pages.
> -b. The infrastructure allows easy addition of other types of memory to control
> -c. Provides *zero overhead* for non memory controller users
> -d. Provides a double LRU: global memory pressure causes reclaim from the
> -   global LRU; a cgroup on hitting a limit, reclaims from the per
> -   cgroup LRU
> -
>  Benefits and Purpose of the memory controller
>
>  The memory controller isolates the memory behaviour of a group of tasks
> @@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
>  e. There are several other use cases, find one or use the controller just
>    for fun (to learn and hack on the VM subsystem).
>
> +Current Status: linux-2.6.34-mmotom(2010/March)
> +
> +Features:
> + - accounting anonymous pages, file caches, swap caches usage and limit them.
> + - private LRU and reclaim routine. (system's global LRU and private LRU
> +   work independently from each other)
> + - optionaly, memory+swap usage
> + - hierarchical accounting
> + - softlimit
> + - moving(recharging) account at moving a task
> + - usage threshold notifier
> + - oom-killer disable and oom-notifier
> + - Root cgroup has no limit controls.
> +
> + Kernel memory and Hugepages are not under control yet. We just manage
> + pages on LRU. To add more controls, we have to take care of performance.
> +
> +Brief summary of control files.
> +
> + tasks                         # attach a task(thread)
> + cgroup.procs                  # attach a process(all threads under it)
> + cgroup.event_control          # an interface for event_fd()
> + memory.usage_in_bytes         # show current memory(RSS+Cache) usage.
> + memory.memsw.usage_in_bytes   # show current memory+Swap usage.
> + memory.limit_in_bytes         # set/show limit of memory usage
> + memory.memsw.limit_in_bytes   # set/show limit of memory+Swap usage.
> + memory.failcnt                        # show the number of memory usage hit limits.
> + memory.memsw.failcnt          # show the number of memory+Swap hit limits.
> + memory.max_usage_in_bytes     # show max memory usage recorded.
> + memory.memsw.usage_in_bytes   # show max memory+Swap usage recorded.
> + memory.stat                   # show various statistics.
> + memory.use_hierarchy          # set/show hierarchical account enabled.
> + memory.force_empty            # trigger forced move charge to parent.
> + memory.swappiness             # set/show swappiness parameter of vmscan
> +                                 (See sysctl's vm.swappiness)
> + memory.move_charge_at_immigrate# set/show controls of moving charges
> + memory.oom_control            # set/show oom controls.
> +
>  1. History
>
>  The memory controller has a long history. A request for comments for the memory
>
> --
> 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>

Two comments:
1. Should we also include a description of the
memory.soft_limit_in_bytes control file in the "Brief summary"
section?

2. the subject of this thread misspelled "documentation
(s/documentaion/documentation/).  Not a problem, but you might want to
fix it for eventually patch submission.

--
Greg

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Re: [RFC][PATCH] memcg documentaion update

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-03-29 15:42:45]:

> At reading Documentation/cgroup/memory.txt, I felt
> 
>  - old
>  - hard to find it's supported what I want to do
> 
> Hmm..maybe some rewrite will be necessary.
> 
> ==
> Documentation update. We have too much files now....
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  Documentation/cgroups/memory.txt |   48 ++++++++++++++++++++++++++++++---------
>  1 file changed, 38 insertions(+), 10 deletions(-)
> 
> Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> @@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
>  to as the memory controller in this document. Do not confuse memory controller
>  used here with the memory controller that is used in hardware.
> 
> -Salient features
> -
> -a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
> -   Swap Cache memory pages.
> -b. The infrastructure allows easy addition of other types of memory to control
> -c. Provides *zero overhead* for non memory controller users
> -d. Provides a double LRU: global memory pressure causes reclaim from the
> -   global LRU; a cgroup on hitting a limit, reclaims from the per
> -   cgroup LRU
> -
>  Benefits and Purpose of the memory controller
> 
>  The memory controller isolates the memory behaviour of a group of tasks
> @@ -33,6 +23,44 @@ d. A CD/DVD burner could control the amo
>  e. There are several other use cases, find one or use the controller just
>     for fun (to learn and hack on the VM subsystem).
> 
> +Current Status: linux-2.6.34-mmotom(2010/March)
> +
> +Features:
> + - accounting anonymous pages, file caches, swap caches usage and limit them.
> + - private LRU and reclaim routine. (system's global LRU and private LRU
> +   work independently from each other)
> + - optionaly, memory+swap usage
> + - hierarchical accounting
> + - softlimit
> + - moving(recharging) account at moving a task
> + - usage threshold notifier
> + - oom-killer disable and oom-notifier
> + - Root cgroup has no limit controls.
> +

Good updates, I saw that you got good review comments already on this.
In the internals section at some point we need to document new
page_cgroup changes, changes to accounting, etc.

> + Kernel memory and Hugepages are not under control yet. We just manage
> + pages on LRU. To add more controls, we have to take care of performance.
> +
> +Brief summary of control files.
> +
> + tasks				# attach a task(thread)
> + cgroup.procs			# attach a process(all threads under it)
> + cgroup.event_control		# an interface for event_fd()
> + memory.usage_in_bytes		# show current memory(RSS+Cache) usage.
> + memory.memsw.usage_in_bytes	# show current memory+Swap usage.
> + memory.limit_in_bytes		# set/show limit of memory usage
> + memory.memsw.limit_in_bytes	# set/show limit of memory+Swap usage.
> + memory.failcnt			# show the number of memory usage hit limits.
> + memory.memsw.failcnt		# show the number of memory+Swap hit limits.
> + memory.max_usage_in_bytes	# show max memory usage recorded.
> + memory.memsw.usage_in_bytes	# show max memory+Swap usage recorded.
> + memory.stat			# show various statistics.
> + memory.use_hierarchy		# set/show hierarchical account enabled.
> + memory.force_empty		# trigger forced move charge to parent.
> + memory.swappiness		# set/show swappiness parameter of vmscan
> + 				  (See sysctl's vm.swappiness)
> + memory.move_charge_at_immigrate# set/show controls of moving charges
> + memory.oom_control		# set/show oom controls.
> +
>  1. History
> 
>  The memory controller has a long history. A request for comments for the memory
> 

-- 
	Three Cheers,
	Balbir

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[RFC][PATCH] memcg documentation update v2

[KAMEZAWA Hiroyuki]

Added more changes since v1. 
I'm not in hurry, please see when you have free time.

==
Documentation update. We have too much files now....

Changlog:
 - added memory.soft_limit_in_bytes to summary.
 - rewrite Testing section
 - fixed text about page_cgroup allocation
 - passed aspell(1) ;)
 - rewrote Locking section
 - update memory.stat file explanation

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 Documentation/cgroups/memory.txt |  187 ++++++++++++++++++++++++++++-----------
 1 file changed, 139 insertions(+), 48 deletions(-)

Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
===================================================================
--- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
+++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
@@ -4,16 +4,6 @@ NOTE: The Memory Resource Controller has
 to as the memory controller in this document. Do not confuse memory controller
 used here with the memory controller that is used in hardware.
 
-Salient features
-
-a. Enable control of Anonymous, Page Cache (mapped and unmapped) and
-   Swap Cache memory pages.
-b. The infrastructure allows easy addition of other types of memory to control
-c. Provides *zero overhead* for non memory controller users
-d. Provides a double LRU: global memory pressure causes reclaim from the
-   global LRU; a cgroup on hitting a limit, reclaims from the per
-   cgroup LRU
-
 Benefits and Purpose of the memory controller
 
 The memory controller isolates the memory behaviour of a group of tasks
@@ -33,6 +23,45 @@ d. A CD/DVD burner could control the amo
 e. There are several other use cases, find one or use the controller just
    for fun (to learn and hack on the VM subsystem).
 
+Current Status: linux-2.6.34-mmotom(development version of 2010/March)
+
+Features:
+ - accounting anonymous pages, file caches, swap caches usage and limit them.
+ - private LRU and reclaim routine. (system's global LRU and private LRU
+   work independently from each other)
+ - optionally, memory+swap usage can be accounted and limited.
+ - hierarchical accounting
+ - soft limit
+ - moving(recharging) account at moving a task is selectable.
+ - usage threshold notifier
+ - oom-killer disable knob and oom-notifier
+ - Root cgroup has no limit controls.
+
+ Kernel memory and Hugepages are not under control yet. We just manage
+ pages on LRU. To add more controls, we have to take care of performance.
+
+Brief summary of control files.
+
+ tasks				 # attach a task(thread)
+ cgroup.procs			 # attach a process(all threads under it)
+ cgroup.event_control		 # an interface for event_fd()
+ memory.usage_in_bytes		 # show current memory(RSS+Cache) usage.
+ memory.memsw.usage_in_bytes	 # show current memory+Swap usage
+ memory.limit_in_bytes		 # set/show limit of memory usage
+ memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage
+ memory.failcnt			 # show the number of memory usage hit limits
+ memory.memsw.failcnt		 # show the number of memory+Swap hit limits
+ memory.max_usage_in_bytes	 # show max memory usage recorded
+ memory.memsw.usage_in_bytes	 # show max memory+Swap usage recorded
+ memory.soft_limit_in_bytes	 # set/show soft limit of memory usage
+ memory.stat			 # show various statistics
+ memory.use_hierarchy		 # set/show hierarchical account enabled
+ memory.force_empty		 # trigger forced move charge to parent
+ memory.swappiness		 # set/show swappiness parameter of vmscan
+ 				  (See sysctl's vm.swappiness)
+ memory.move_charge_at_immigrate # set/show controls of moving charges
+ memory.oom_control		 # set/show oom controls.
+
 1. History
 
 The memory controller has a long history. A request for comments for the memory
@@ -106,14 +135,14 @@ the necessary data structures and check 
 is over its limit. If it is then reclaim is invoked on the cgroup.
 More details can be found in the reclaim section of this document.
 If everything goes well, a page meta-data-structure called page_cgroup is
-allocated and associated with the page.  This routine also adds the page to
-the per cgroup LRU.
+updated. page_cgroup has its own LRU on cgroup.
+(*) page_cgroup structure is allocated at boot/memory-hotplug time.
 
 2.2.1 Accounting details
 
 All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
-(some pages which never be reclaimable and will not be on global LRU
- are not accounted. we just accounts pages under usual vm management.)
+Some pages which never be reclaimable and will not be on global LRU
+are not accounted. we just accounts pages under usual vm management.
 
 RSS pages are accounted at page_fault unless they've already been accounted
 for earlier. A file page will be accounted for as Page Cache when it's
@@ -121,7 +150,12 @@ inserted into inode (radix-tree). While 
 processes, duplicate accounting is carefully avoided.
 
 A RSS page is unaccounted when it's fully unmapped. A PageCache page is
-unaccounted when it's removed from radix-tree.
+unaccounted when it's removed from radix-tree. Even if RSS pages are fully
+unmapped (by kswapd), it may exist as SwapCache in the system until it really
+freed. Such SwapCache is also accounted. Swapped-in pages are not accounted
+until it's mapped. This is because of swapin-readahead.
+
+A Cache pages is unaccounted when it's removed from inode (radix-tree).
 
 At page migration, accounting information is kept.
 
@@ -143,6 +177,7 @@ caller of swapoff rather than the users 
 
 
 2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
+
 Swap Extension allows you to record charge for swap. A swapped-in page is
 charged back to original page allocator if possible.
 
@@ -150,9 +185,15 @@ When swap is accounted, following files 
  - memory.memsw.usage_in_bytes.
  - memory.memsw.limit_in_bytes.
 
-usage of mem+swap is limited by memsw.limit_in_bytes.
+memsw means memory+swap. Usage of mem+swap is limited by memsw.limit_in_bytes.
 
-* why 'mem+swap' rather than swap.
+example) Assume a system with 4G of swap. A task which allocates 6G of memory
+(by mistake) under 2G memory limitation will use all swap.
+In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap.
+(bad process will cause OOM under the memcg. you can avoid system OOM because
+ of no swap.)
+
+* why 'memory+swap' rather than swap.
 The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
 to move account from memory to swap...there is no change in usage of
 mem+swap. In other words, when we want to limit the usage of swap without
@@ -168,12 +209,12 @@ it by cgroup.
 
 2.5 Reclaim
 
-Each cgroup maintains a per cgroup LRU that consists of an active
-and inactive list. When a cgroup goes over its limit, we first try
+Each cgroup maintains a per cgroup LRU which has the same structure as
+global VM. When a cgroup goes over its limit, we first try
 to reclaim memory from the cgroup so as to make space for the new
 pages that the cgroup has touched. If the reclaim is unsuccessful,
 an OOM routine is invoked to select and kill the bulkiest task in the
-cgroup.
+cgroup. (See 10. OOM Control below.)
 
 The reclaim algorithm has not been modified for cgroups, except that
 pages that are selected for reclaiming come from the per cgroup LRU
@@ -189,11 +230,17 @@ When oom event notifier is registered, e
 
 2. Locking
 
-The memory controller uses the following hierarchy
+   lock_page_cgroup()/unlock_page_cgroup() should not be called under
+   mapping->tree_lock.
 
-1. zone->lru_lock is used for selecting pages to be isolated
-2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
-3. lock_page_cgroup() is used to protect page->page_cgroup
+   Other lock order is following.
+   PG_locked.
+   mm->page_table_lock
+       zone->lru_lock
+	  lock_page_cgroup.
+  In many case, just lock_page_cgroup() is called.
+  per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
+  zone->lru_lock, it has no its own lock.
 
 3. User Interface
 
@@ -202,6 +249,7 @@ The memory controller uses the following
 a. Enable CONFIG_CGROUPS
 b. Enable CONFIG_RESOURCE_COUNTERS
 c. Enable CONFIG_CGROUP_MEM_RES_CTLR
+d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension)
 
 1. Prepare the cgroups
 # mkdir -p /cgroups
@@ -216,16 +264,14 @@ We can alter the memory limit:
 # echo 4M > /cgroups/0/memory.limit_in_bytes
 
 NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
-mega or gigabytes.
+mega or gigabytes. (Here, Kilo, Mega, Giga is Kibibytes, Mebibytes, Gibibytes)
+
 NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
 NOTE: We cannot set limits on the root cgroup any more.
 
 # cat /cgroups/0/memory.limit_in_bytes
 4194304
 
-NOTE: The interface has now changed to display the usage in bytes
-instead of pages
-
 We can check the usage:
 # cat /cgroups/0/memory.usage_in_bytes
 1216512
@@ -248,15 +294,24 @@ caches, RSS and Active pages/Inactive pa
 
 4. Testing
 
-Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
-Apart from that v6 has been tested with several applications and regular
-daily use. The controller has also been tested on the PPC64, x86_64 and
-UML platforms.
+For testing feature and implementation, see memcg_test.txt.
+
+Performance test is also important. To see pure memcg's overhead,
+testing om tmpfs will give you good numbers of small overheads.
+example) do kernel make on tmpfs.
+
+Page-fault scalability is also important. At measuring pararell
+page fault test, multi-process test may be better than multi-thread
+test because multi-thread shares something and need sync.
+
+But above 2 is testing extreme situation. Trying usual test under memcg
+is always helpful.
+
 
 4.1 Troubleshooting
 
 Sometimes a user might find that the application under a cgroup is
-terminated. There are several causes for this:
+terminated by OOM killer. There are several causes for this:
 
 1. The cgroup limit is too low (just too low to do anything useful)
 2. The user is using anonymous memory and swap is turned off or too low
@@ -264,6 +319,9 @@ terminated. There are several causes for
 A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of
 some of the pages cached in the cgroup (page cache pages).
 
+To know what happens, disable OOM_Kill by 10.OOM Control(see below) and
+see what happens will be a help.
+
 4.2 Task migration
 
 When a task migrates from one cgroup to another, it's charge is not
@@ -271,16 +329,19 @@ carried forward by default. The pages al
 remain charged to it, the charge is dropped when the page is freed or
 reclaimed.
 
-Note: You can move charges of a task along with task migration. See 8.
+You can move charges of a task along with task migration.
+See 8. "Move charges at task migration"
 
 4.3 Removing a cgroup
 
 A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
 cgroup might have some charge associated with it, even though all
-tasks have migrated away from it.
-Such charges are freed(at default) or moved to its parent. When moved,
-both of RSS and CACHES are moved to parent.
-If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also.
+tasks have migrated away from it. (because we charge against pages, not
+against tasks.)
+
+Such charges are freed or moved to its parent. At moving, both of RSS
+and CACHES are moved to parent.
+rmdir() may return -EBUSY if freeing/moving fails. See 5.1 Also.
 
 Charges recorded in swap information is not updated at removal of cgroup.
 Recorded information is discarded and a cgroup which uses swap (swapcache)
@@ -309,19 +370,41 @@ will be charged as a new owner of it.
 
 memory.stat file includes following statistics
 
+# per-memcg local status
 cache		- # of bytes of page cache memory.
 rss		- # of bytes of anonymous and swap cache memory.
+mapped_file	- # of bytes of mapped file (includes tmpfs/shmem)
 pgpgin		- # of pages paged in (equivalent to # of charging events).
 pgpgout		- # of pages paged out (equivalent to # of uncharging events).
-active_anon	- # of bytes of anonymous and  swap cache memory on active
-		  lru list.
+swap		- # of bytes of swap usage
 inactive_anon	- # of bytes of anonymous memory and swap cache memory on
+		  lru list.
+active_anon	- # of bytes of anonymous and  swap cache memory on active
 		  inactive lru list.
-active_file	- # of bytes of file-backed memory on active lru list.
 inactive_file	- # of bytes of file-backed memory on inactive lru list.
+active_file	- # of bytes of file-backed memory on active lru list.
 unevictable	- # of bytes of memory that cannot be reclaimed (mlocked etc).
 
-The following additional stats are dependent on CONFIG_DEBUG_VM.
+# status considering hierarchy (see memory.use_hierarchy settings)
+
+hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
+			under which the memcg is
+hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
+			hierarchy under which memcg is.
+
+total_cache		- sum of all children's "cache"
+total_rss		- sum of all children's "rss"
+total_mapped_file	- sum of all children's "cache"
+total_pgpgin		- sum of all children's "pgpgin"
+total_pgpgout		- sum of all children's "pgpgout"
+total_swap		- sum of all children's "swap"
+total_inactive_anon	- sum of all children's "inactive_anon"
+total_active_anon	- sum of all children's "active_anon"
+total_inactive_file	- sum of all children's "inactive_file"
+total_active_file	- sum of all children's "active_file"
+total_unevictable	- sum of all children's "unevictable"
+
+# The following additional stats are dependent on CONFIG_DEBUG_VM.
 
 inactive_ratio		- VM internal parameter. (see mm/page_alloc.c)
 recent_rotated_anon	- VM internal parameter. (see mm/vmscan.c)
@@ -337,17 +420,25 @@ Memo:
 Note:
 	Only anonymous and swap cache memory is listed as part of 'rss' stat.
 	This should not be confused with the true 'resident set size' or the
-	amount of physical memory used by the cgroup. Per-cgroup rss
-	accounting is not done yet.
+	amount of physical memory used by the cgroup.
+	'rss + file_mapped" will give you resident set size of cgroup.
+	(Note: file and shmem may be shared amoung other cgroups. In that case,
+	 file_mapped is accounted only when the memcg is owner of page cache.)
 
 5.3 swappiness
   Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
 
   Following cgroups' swappiness can't be changed.
   - root cgroup (uses /proc/sys/vm/swappiness).
-  - a cgroup which uses hierarchy and it has child cgroup.
+  - a cgroup which uses hierarchy and it has other cgroup(s) below it.
   - a cgroup which uses hierarchy and not the root of hierarchy.
 
+5.4 failcnt
+
+The memory controller provides memory.failcnt and memory.memsw.failcnt files.
+This failcnt(== failure count) shows the number of events that usage counter
+hit limits. When a memory controller hit limit, failcnt increase and memory
+under it will be reclaimed.
 
 6. Hierarchy support
 
@@ -395,7 +486,7 @@ is to allow control groups to use as muc
 a. There is no memory contention
 b. They do not exceed their hard limit
 
-When the system detects memory contention or low memory control groups
+When the system detects memory contention or low memory, control groups
 are pushed back to their soft limits. If the soft limit of each control
 group is very high, they are pushed back as much as possible to make
 sure that one control group does not starve the others of memory.
@@ -409,7 +500,7 @@ it gets invoked from balance_pgdat (kswa
 7.1 Interface
 
 Soft limits can be setup by using the following commands (in this example we
-assume a soft limit of 256 megabytes)
+assume a soft limit of 256 MiB)
 
 # echo 256M > memory.soft_limit_in_bytes
 
@@ -445,7 +536,7 @@ Note: Charges are moved only when you mo
 Note: If we cannot find enough space for the task in the destination cgroup, we
       try to make space by reclaiming memory. Task migration may fail if we
       cannot make enough space.
-Note: It can take several seconds if you move charges in giga bytes order.
+Note: It can take several seconds if you move charges much.
 
 And if you want disable it again:
 

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Re: [RFC][PATCH] memcg documentation update v2

[Randy Dunlap]

On Wed, 31 Mar 2010 17:51:57 +0900 KAMEZAWA Hiroyuki wrote:

> Added more changes since v1. 
> I'm not in hurry, please see when you have free time.

OK, I have some comments for you to consider.


> ==
> Documentation update. We have too much files now....
> 
> Changlog:
>  - added memory.soft_limit_in_bytes to summary.
>  - rewrite Testing section
>  - fixed text about page_cgroup allocation
>  - passed aspell(1) ;)
>  - rewrote Locking section
>  - update memory.stat file explanation
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  Documentation/cgroups/memory.txt |  187 ++++++++++++++++++++++++++++-----------
>  1 file changed, 139 insertions(+), 48 deletions(-)
> 
> Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> ===================================================================
> --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt

> @@ -33,6 +23,45 @@ d. A CD/DVD burner could control the amo
>  e. There are several other use cases, find one or use the controller just
>     for fun (to learn and hack on the VM subsystem).
>  
> +Current Status: linux-2.6.34-mmotom(development version of 2010/March)

                               -mmotm

> +
> +Features:
> + - accounting anonymous pages, file caches, swap caches usage and limit them.
> + - private LRU and reclaim routine. (system's global LRU and private LRU
> +   work independently from each other)
> + - optionally, memory+swap usage can be accounted and limited.
> + - hierarchical accounting
> + - soft limit
> + - moving(recharging) account at moving a task is selectable.
> + - usage threshold notifier
> + - oom-killer disable knob and oom-notifier
> + - Root cgroup has no limit controls.
> +
> + Kernel memory and Hugepages are not under control yet. We just manage
> + pages on LRU. To add more controls, we have to take care of performance.
> +
> +Brief summary of control files.
> +
> + tasks				 # attach a task(thread)
> + cgroup.procs			 # attach a process(all threads under it)
> + cgroup.event_control		 # an interface for event_fd()
> + memory.usage_in_bytes		 # show current memory(RSS+Cache) usage.
> + memory.memsw.usage_in_bytes	 # show current memory+Swap usage
> + memory.limit_in_bytes		 # set/show limit of memory usage
> + memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage
> + memory.failcnt			 # show the number of memory usage hit limits
> + memory.memsw.failcnt		 # show the number of memory+Swap hit limits
> + memory.max_usage_in_bytes	 # show max memory usage recorded
> + memory.memsw.usage_in_bytes	 # show max memory+Swap usage recorded
> + memory.soft_limit_in_bytes	 # set/show soft limit of memory usage
> + memory.stat			 # show various statistics
> + memory.use_hierarchy		 # set/show hierarchical account enabled
> + memory.force_empty		 # trigger forced move charge to parent
> + memory.swappiness		 # set/show swappiness parameter of vmscan
> + 				  (See sysctl's vm.swappiness)
> + memory.move_charge_at_immigrate # set/show controls of moving charges
> + memory.oom_control		 # set/show oom controls.
> +
>  1. History
>  
>  The memory controller has a long history. A request for comments for the memory
> @@ -106,14 +135,14 @@ the necessary data structures and check 
>  is over its limit. If it is then reclaim is invoked on the cgroup.
>  More details can be found in the reclaim section of this document.
>  If everything goes well, a page meta-data-structure called page_cgroup is
> -allocated and associated with the page.  This routine also adds the page to
> -the per cgroup LRU.
> +updated. page_cgroup has its own LRU on cgroup.
> +(*) page_cgroup structure is allocated at boot/memory-hotplug time.
>  
>  2.2.1 Accounting details
>  
>  All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
> -(some pages which never be reclaimable and will not be on global LRU
> - are not accounted. we just accounts pages under usual vm management.)
> +Some pages which never be reclaimable and will not be on global LRU

Awkward sentence above.  Maybe:

   Some pages which are never reclaimable and will not be on the global LRU

> +are not accounted. we just accounts pages under usual vm management.

                      We just account

Prefer "VM" to "vm". (multiple places)

>  
>  RSS pages are accounted at page_fault unless they've already been accounted
>  for earlier. A file page will be accounted for as Page Cache when it's
> @@ -121,7 +150,12 @@ inserted into inode (radix-tree). While 
>  processes, duplicate accounting is carefully avoided.
>  
>  A RSS page is unaccounted when it's fully unmapped. A PageCache page is
> -unaccounted when it's removed from radix-tree.
> +unaccounted when it's removed from radix-tree. Even if RSS pages are fully
> +unmapped (by kswapd), it may exist as SwapCache in the system until it really

                         they                                          they are really

> +freed. Such SwapCache is also accounted. Swapped-in pages are not accounted
> +until it's mapped. This is because of swapin-readahead.

         they are mapped.

> +
> +A Cache pages is unaccounted when it's removed from inode (radix-tree).

           page

>  
>  At page migration, accounting information is kept.
>  
> @@ -143,6 +177,7 @@ caller of swapoff rather than the users 
>  
>  
>  2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
> +
>  Swap Extension allows you to record charge for swap. A swapped-in page is
>  charged back to original page allocator if possible.
>  
> @@ -150,9 +185,15 @@ When swap is accounted, following files 
>   - memory.memsw.usage_in_bytes.
>   - memory.memsw.limit_in_bytes.
>  
> -usage of mem+swap is limited by memsw.limit_in_bytes.
> +memsw means memory+swap. Usage of mem+swap is limited by memsw.limit_in_bytes.

OK, you define "memsw" as memory+swap, then use "mem+swap".  Is that the
same thing?  If so, I would use one of the first 2 choices and drop the last one
instead of having 3 phrases that mean the same thing.

>  
> -* why 'mem+swap' rather than swap.
> +example) Assume a system with 4G of swap. A task which allocates 6G of memory
> +(by mistake) under 2G memory limitation will use all swap.
> +In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap.
> +(bad process will cause OOM under the memcg. you can avoid system OOM because

    Bad                                         You

> + of no swap.)
> +
> +* why 'memory+swap' rather than swap.
>  The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
>  to move account from memory to swap...there is no change in usage of
>  mem+swap. In other words, when we want to limit the usage of swap without
> @@ -168,12 +209,12 @@ it by cgroup.
>  
>  2.5 Reclaim
>  
> -Each cgroup maintains a per cgroup LRU that consists of an active
> -and inactive list. When a cgroup goes over its limit, we first try
> +Each cgroup maintains a per cgroup LRU which has the same structure as
> +global VM. When a cgroup goes over its limit, we first try
>  to reclaim memory from the cgroup so as to make space for the new
>  pages that the cgroup has touched. If the reclaim is unsuccessful,
>  an OOM routine is invoked to select and kill the bulkiest task in the
> -cgroup.
> +cgroup. (See 10. OOM Control below.)
>  
>  The reclaim algorithm has not been modified for cgroups, except that
>  pages that are selected for reclaiming come from the per cgroup LRU
> @@ -189,11 +230,17 @@ When oom event notifier is registered, e
>  
>  2. Locking
>  
> -The memory controller uses the following hierarchy
> +   lock_page_cgroup()/unlock_page_cgroup() should not be called under
> +   mapping->tree_lock.
>  
> -1. zone->lru_lock is used for selecting pages to be isolated
> -2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
> -3. lock_page_cgroup() is used to protect page->page_cgroup
> +   Other lock order is following.

                          following:

> +   PG_locked.
> +   mm->page_table_lock
> +       zone->lru_lock
> +	  lock_page_cgroup.
> +  In many case, just lock_page_cgroup() is called.

             cases,

> +  per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
> +  zone->lru_lock, it has no its own lock.

                     it has no lock of its own.

>  
>  3. User Interface
>  
> @@ -202,6 +249,7 @@ The memory controller uses the following
>  a. Enable CONFIG_CGROUPS
>  b. Enable CONFIG_RESOURCE_COUNTERS
>  c. Enable CONFIG_CGROUP_MEM_RES_CTLR
> +d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension)
>  
>  1. Prepare the cgroups
>  # mkdir -p /cgroups
> @@ -216,16 +264,14 @@ We can alter the memory limit:
>  # echo 4M > /cgroups/0/memory.limit_in_bytes
>  
>  NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
> -mega or gigabytes.
> +mega or gigabytes. (Here, Kilo, Mega, Giga is Kibibytes, Mebibytes, Gibibytes)

                                              are                       ...bytes.)

> +
>  NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
>  NOTE: We cannot set limits on the root cgroup any more.
>  
>  # cat /cgroups/0/memory.limit_in_bytes
>  4194304
>  
> -NOTE: The interface has now changed to display the usage in bytes
> -instead of pages
> -
>  We can check the usage:
>  # cat /cgroups/0/memory.usage_in_bytes
>  1216512
> @@ -248,15 +294,24 @@ caches, RSS and Active pages/Inactive pa
>  
>  4. Testing
>  
> -Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
> -Apart from that v6 has been tested with several applications and regular
> -daily use. The controller has also been tested on the PPC64, x86_64 and
> -UML platforms.
> +For testing feature and implementation, see memcg_test.txt.

               features

> +
> +Performance test is also important. To see pure memcg's overhead,
> +testing om tmpfs will give you good numbers of small overheads.
> +example) do kernel make on tmpfs.

  Example:

> +
> +Page-fault scalability is also important. At measuring pararell

                                                          parallel

> +page fault test, multi-process test may be better than multi-thread
> +test because multi-thread shares something and need sync.
> +
> +But above 2 is testing extreme situation. Trying usual test under memcg
> +is always helpful.
> +
>  
>  4.1 Troubleshooting
>  
>  Sometimes a user might find that the application under a cgroup is
> -terminated. There are several causes for this:
> +terminated by OOM killer. There are several causes for this:
>  
>  1. The cgroup limit is too low (just too low to do anything useful)
>  2. The user is using anonymous memory and swap is turned off or too low
> @@ -264,6 +319,9 @@ terminated. There are several causes for
>  A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of
>  some of the pages cached in the cgroup (page cache pages).
>  
> +To know what happens, disable OOM_Kill by 10.OOM Control(see below) and

           insert space:                     10. OOM Control

> +see what happens will be a help.

   seeing what happens will be helpful.

> +
>  4.2 Task migration
>  
>  When a task migrates from one cgroup to another, it's charge is not
> @@ -271,16 +329,19 @@ carried forward by default. The pages al
>  remain charged to it, the charge is dropped when the page is freed or
>  reclaimed.
>  
> -Note: You can move charges of a task along with task migration. See 8.
> +You can move charges of a task along with task migration.
> +See 8. "Move charges at task migration"
>  
>  4.3 Removing a cgroup
>  
>  A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
>  cgroup might have some charge associated with it, even though all
> -tasks have migrated away from it.
> -Such charges are freed(at default) or moved to its parent. When moved,
> -both of RSS and CACHES are moved to parent.
> -If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also.
> +tasks have migrated away from it. (because we charge against pages, not
> +against tasks.)
> +
> +Such charges are freed or moved to its parent. At moving, both of RSS

                                      their

> +and CACHES are moved to parent.
> +rmdir() may return -EBUSY if freeing/moving fails. See 5.1 Also.

                                                              also.

>  
>  Charges recorded in swap information is not updated at removal of cgroup.
>  Recorded information is discarded and a cgroup which uses swap (swapcache)
> @@ -309,19 +370,41 @@ will be charged as a new owner of it.
>  
>  memory.stat file includes following statistics
>  
> +# per-memcg local status
>  cache		- # of bytes of page cache memory.
>  rss		- # of bytes of anonymous and swap cache memory.
> +mapped_file	- # of bytes of mapped file (includes tmpfs/shmem)
>  pgpgin		- # of pages paged in (equivalent to # of charging events).
>  pgpgout		- # of pages paged out (equivalent to # of uncharging events).
> -active_anon	- # of bytes of anonymous and  swap cache memory on active
> -		  lru list.
> +swap		- # of bytes of swap usage
>  inactive_anon	- # of bytes of anonymous memory and swap cache memory on
> +		  lru list.
> +active_anon	- # of bytes of anonymous and  swap cache memory on active
>  		  inactive lru list.
> -active_file	- # of bytes of file-backed memory on active lru list.
>  inactive_file	- # of bytes of file-backed memory on inactive lru list.
> +active_file	- # of bytes of file-backed memory on active lru list.
>  unevictable	- # of bytes of memory that cannot be reclaimed (mlocked etc).
>  
> -The following additional stats are dependent on CONFIG_DEBUG_VM.
> +# status considering hierarchy (see memory.use_hierarchy settings)
> +
> +hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
> +			under which the memcg is
> +hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
> +			hierarchy under which memcg is.
> +
> +total_cache		- sum of all children's "cache"
> +total_rss		- sum of all children's "rss"
> +total_mapped_file	- sum of all children's "cache"
> +total_pgpgin		- sum of all children's "pgpgin"
> +total_pgpgout		- sum of all children's "pgpgout"
> +total_swap		- sum of all children's "swap"
> +total_inactive_anon	- sum of all children's "inactive_anon"
> +total_active_anon	- sum of all children's "active_anon"
> +total_inactive_file	- sum of all children's "inactive_file"
> +total_active_file	- sum of all children's "active_file"
> +total_unevictable	- sum of all children's "unevictable"
> +
> +# The following additional stats are dependent on CONFIG_DEBUG_VM.
>  
>  inactive_ratio		- VM internal parameter. (see mm/page_alloc.c)
>  recent_rotated_anon	- VM internal parameter. (see mm/vmscan.c)
> @@ -337,17 +420,25 @@ Memo:
>  Note:
>  	Only anonymous and swap cache memory is listed as part of 'rss' stat.
>  	This should not be confused with the true 'resident set size' or the
> -	amount of physical memory used by the cgroup. Per-cgroup rss
> -	accounting is not done yet.
> +	amount of physical memory used by the cgroup.
> +	'rss + file_mapped" will give you resident set size of cgroup.
> +	(Note: file and shmem may be shared amoung other cgroups. In that case,
> +	 file_mapped is accounted only when the memcg is owner of page cache.)
>  
>  5.3 swappiness
>    Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
>  
>    Following cgroups' swappiness can't be changed.
>    - root cgroup (uses /proc/sys/vm/swappiness).
> -  - a cgroup which uses hierarchy and it has child cgroup.
> +  - a cgroup which uses hierarchy and it has other cgroup(s) below it.
>    - a cgroup which uses hierarchy and not the root of hierarchy.
>  
> +5.4 failcnt
> +
> +The memory controller provides memory.failcnt and memory.memsw.failcnt files.
> +This failcnt(== failure count) shows the number of events that usage counter

                                  shows the number of times that a usage counter

> +hit limits. When a memory controller hit limit, failcnt increase and memory

   hit its limit. When a memory controller hits a limit, failcnt increases and memory

> +under it will be reclaimed.
>  
>  6. Hierarchy support
>  


HTH.

---
~Randy

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Re: [RFC][PATCH] memcg documentation update v2

[KAMEZAWA Hiroyuki]

On Wed, 31 Mar 2010 10:27:26 -0700
Randy Dunlap <randy.dunlap@oracle.com> wrote:

> On Wed, 31 Mar 2010 17:51:57 +0900 KAMEZAWA Hiroyuki wrote:
> 
> > Added more changes since v1. 
> > I'm not in hurry, please see when you have free time.
> 
> OK, I have some comments for you to consider.
> 
Thank you!

> 
> > ==
> > Documentation update. We have too much files now....
> > 
> > Changlog:
> >  - added memory.soft_limit_in_bytes to summary.
> >  - rewrite Testing section
> >  - fixed text about page_cgroup allocation
> >  - passed aspell(1) ;)
> >  - rewrote Locking section
> >  - update memory.stat file explanation
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  Documentation/cgroups/memory.txt |  187 ++++++++++++++++++++++++++++-----------
> >  1 file changed, 139 insertions(+), 48 deletions(-)
> > 
> > Index: mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> > ===================================================================
> > --- mmotm-2.6.34-Mar24.orig/Documentation/cgroups/memory.txt
> > +++ mmotm-2.6.34-Mar24/Documentation/cgroups/memory.txt
> 
> > @@ -33,6 +23,45 @@ d. A CD/DVD burner could control the amo
> >  e. There are several other use cases, find one or use the controller just
> >     for fun (to learn and hack on the VM subsystem).
> >  
> > +Current Status: linux-2.6.34-mmotom(development version of 2010/March)
> 
>                                -mmotm
> 
Ah...ok.

> > +
> > +Features:
> > + - accounting anonymous pages, file caches, swap caches usage and limit them.
> > + - private LRU and reclaim routine. (system's global LRU and private LRU
> > +   work independently from each other)
> > + - optionally, memory+swap usage can be accounted and limited.
> > + - hierarchical accounting
> > + - soft limit
> > + - moving(recharging) account at moving a task is selectable.
> > + - usage threshold notifier
> > + - oom-killer disable knob and oom-notifier
> > + - Root cgroup has no limit controls.
> > +
> > + Kernel memory and Hugepages are not under control yet. We just manage
> > + pages on LRU. To add more controls, we have to take care of performance.
> > +
> > +Brief summary of control files.
> > +
> > + tasks				 # attach a task(thread)
> > + cgroup.procs			 # attach a process(all threads under it)
> > + cgroup.event_control		 # an interface for event_fd()
> > + memory.usage_in_bytes		 # show current memory(RSS+Cache) usage.
> > + memory.memsw.usage_in_bytes	 # show current memory+Swap usage
> > + memory.limit_in_bytes		 # set/show limit of memory usage
> > + memory.memsw.limit_in_bytes	 # set/show limit of memory+Swap usage
> > + memory.failcnt			 # show the number of memory usage hit limits
> > + memory.memsw.failcnt		 # show the number of memory+Swap hit limits
> > + memory.max_usage_in_bytes	 # show max memory usage recorded
> > + memory.memsw.usage_in_bytes	 # show max memory+Swap usage recorded
> > + memory.soft_limit_in_bytes	 # set/show soft limit of memory usage
> > + memory.stat			 # show various statistics
> > + memory.use_hierarchy		 # set/show hierarchical account enabled
> > + memory.force_empty		 # trigger forced move charge to parent
> > + memory.swappiness		 # set/show swappiness parameter of vmscan
> > + 				  (See sysctl's vm.swappiness)
> > + memory.move_charge_at_immigrate # set/show controls of moving charges
> > + memory.oom_control		 # set/show oom controls.
> > +
> >  1. History
> >  
> >  The memory controller has a long history. A request for comments for the memory
> > @@ -106,14 +135,14 @@ the necessary data structures and check 
> >  is over its limit. If it is then reclaim is invoked on the cgroup.
> >  More details can be found in the reclaim section of this document.
> >  If everything goes well, a page meta-data-structure called page_cgroup is
> > -allocated and associated with the page.  This routine also adds the page to
> > -the per cgroup LRU.
> > +updated. page_cgroup has its own LRU on cgroup.
> > +(*) page_cgroup structure is allocated at boot/memory-hotplug time.
> >  
> >  2.2.1 Accounting details
> >  
> >  All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
> > -(some pages which never be reclaimable and will not be on global LRU
> > - are not accounted. we just accounts pages under usual vm management.)
> > +Some pages which never be reclaimable and will not be on global LRU
> 
> Awkward sentence above.  Maybe:
> 
>    Some pages which are never reclaimable and will not be on the global LRU
> 
> > +are not accounted. we just accounts pages under usual vm management.
> 
>                       We just account
> 
> Prefer "VM" to "vm". (multiple places)
> 
Sure, will fix.

> >  
> >  RSS pages are accounted at page_fault unless they've already been accounted
> >  for earlier. A file page will be accounted for as Page Cache when it's
> > @@ -121,7 +150,12 @@ inserted into inode (radix-tree). While 
> >  processes, duplicate accounting is carefully avoided.
> >  
> >  A RSS page is unaccounted when it's fully unmapped. A PageCache page is
> > -unaccounted when it's removed from radix-tree.
> > +unaccounted when it's removed from radix-tree. Even if RSS pages are fully
> > +unmapped (by kswapd), it may exist as SwapCache in the system until it really
> 
>                          they                                          they are really
> 
> > +freed. Such SwapCache is also accounted. Swapped-in pages are not accounted
> > +until it's mapped. This is because of swapin-readahead.
> 
>          they are mapped.
> 
ah, yes. "pages"..

> > +
> > +A Cache pages is unaccounted when it's removed from inode (radix-tree).
> 
>            page
> 
will fix.


> >  
> >  At page migration, accounting information is kept.
> >  
> > @@ -143,6 +177,7 @@ caller of swapoff rather than the users 
> >  
> >  
> >  2.4 Swap Extension (CONFIG_CGROUP_MEM_RES_CTLR_SWAP)
> > +
> >  Swap Extension allows you to record charge for swap. A swapped-in page is
> >  charged back to original page allocator if possible.
> >  
> > @@ -150,9 +185,15 @@ When swap is accounted, following files 
> >   - memory.memsw.usage_in_bytes.
> >   - memory.memsw.limit_in_bytes.
> >  
> > -usage of mem+swap is limited by memsw.limit_in_bytes.
> > +memsw means memory+swap. Usage of mem+swap is limited by memsw.limit_in_bytes.
> 
> OK, you define "memsw" as memory+swap, then use "mem+swap".  Is that the
> same thing?  If so, I would use one of the first 2 choices and drop the last one
> instead of having 3 phrases that mean the same thing.
> 
Right. I'll drop mem+swap.


> >  
> > -* why 'mem+swap' rather than swap.
> > +example) Assume a system with 4G of swap. A task which allocates 6G of memory
> > +(by mistake) under 2G memory limitation will use all swap.
> > +In this case, setting memsw.limit_in_bytes=3G will prevent bad use of swap.
> > +(bad process will cause OOM under the memcg. you can avoid system OOM because
> 
>     Bad                                         You
> 
will fix.


> > + of no swap.)
> > +
> > +* why 'memory+swap' rather than swap.
> >  The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
> >  to move account from memory to swap...there is no change in usage of
> >  mem+swap. In other words, when we want to limit the usage of swap without
> > @@ -168,12 +209,12 @@ it by cgroup.
> >  
> >  2.5 Reclaim
> >  
> > -Each cgroup maintains a per cgroup LRU that consists of an active
> > -and inactive list. When a cgroup goes over its limit, we first try
> > +Each cgroup maintains a per cgroup LRU which has the same structure as
> > +global VM. When a cgroup goes over its limit, we first try
> >  to reclaim memory from the cgroup so as to make space for the new
> >  pages that the cgroup has touched. If the reclaim is unsuccessful,
> >  an OOM routine is invoked to select and kill the bulkiest task in the
> > -cgroup.
> > +cgroup. (See 10. OOM Control below.)
> >  
> >  The reclaim algorithm has not been modified for cgroups, except that
> >  pages that are selected for reclaiming come from the per cgroup LRU
> > @@ -189,11 +230,17 @@ When oom event notifier is registered, e
> >  
> >  2. Locking
> >  
> > -The memory controller uses the following hierarchy
> > +   lock_page_cgroup()/unlock_page_cgroup() should not be called under
> > +   mapping->tree_lock.
> >  
> > -1. zone->lru_lock is used for selecting pages to be isolated
> > -2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
> > -3. lock_page_cgroup() is used to protect page->page_cgroup
> > +   Other lock order is following.
> 
>                           following:
> 
ok.

> > +   PG_locked.
> > +   mm->page_table_lock
> > +       zone->lru_lock
> > +	  lock_page_cgroup.
> > +  In many case, just lock_page_cgroup() is called.
> 
>              cases,
> 
Sure.

> > +  per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
> > +  zone->lru_lock, it has no its own lock.
> 
>                      it has no lock of its own.
> 
Will fix.


> >  
> >  3. User Interface
> >  
> > @@ -202,6 +249,7 @@ The memory controller uses the following
> >  a. Enable CONFIG_CGROUPS
> >  b. Enable CONFIG_RESOURCE_COUNTERS
> >  c. Enable CONFIG_CGROUP_MEM_RES_CTLR
> > +d. Enable CONFIG_CGROUP_MEM_RES_CTLR_SWAP (to use swap extension)
> >  
> >  1. Prepare the cgroups
> >  # mkdir -p /cgroups
> > @@ -216,16 +264,14 @@ We can alter the memory limit:
> >  # echo 4M > /cgroups/0/memory.limit_in_bytes
> >  
> >  NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo,
> > -mega or gigabytes.
> > +mega or gigabytes. (Here, Kilo, Mega, Giga is Kibibytes, Mebibytes, Gibibytes)
> 
>                                               are                       ...bytes.)
> 
Will fix.


> > +
> >  NOTE: We can write "-1" to reset the *.limit_in_bytes(unlimited).
> >  NOTE: We cannot set limits on the root cgroup any more.
> >  
> >  # cat /cgroups/0/memory.limit_in_bytes
> >  4194304
> >  
> > -NOTE: The interface has now changed to display the usage in bytes
> > -instead of pages
> > -
> >  We can check the usage:
> >  # cat /cgroups/0/memory.usage_in_bytes
> >  1216512
> > @@ -248,15 +294,24 @@ caches, RSS and Active pages/Inactive pa
> >  
> >  4. Testing
> >  
> > -Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
> > -Apart from that v6 has been tested with several applications and regular
> > -daily use. The controller has also been tested on the PPC64, x86_64 and
> > -UML platforms.
> > +For testing feature and implementation, see memcg_test.txt.
> 
>                features
> 
Will fix.

> > +
> > +Performance test is also important. To see pure memcg's overhead,
> > +testing om tmpfs will give you good numbers of small overheads.
> > +example) do kernel make on tmpfs.
> 
>   Example:
> 
ok.

> > +
> > +Page-fault scalability is also important. At measuring pararell
> 
>                                                           parallel
> 
Ah...thanks.


> > +page fault test, multi-process test may be better than multi-thread
> > +test because multi-thread shares something and need sync.
> > +
> > +But above 2 is testing extreme situation. Trying usual test under memcg
> > +is always helpful.
> > +
> >  
> >  4.1 Troubleshooting
> >  
> >  Sometimes a user might find that the application under a cgroup is
> > -terminated. There are several causes for this:
> > +terminated by OOM killer. There are several causes for this:
> >  
> >  1. The cgroup limit is too low (just too low to do anything useful)
> >  2. The user is using anonymous memory and swap is turned off or too low
> > @@ -264,6 +319,9 @@ terminated. There are several causes for
> >  A sync followed by echo 1 > /proc/sys/vm/drop_caches will help get rid of
> >  some of the pages cached in the cgroup (page cache pages).
> >  
> > +To know what happens, disable OOM_Kill by 10.OOM Control(see below) and
> 
>            insert space:                     10. OOM Control
> 
ok.

> > +see what happens will be a help.
> 
>    seeing what happens will be helpful.
> 
will fix.


> > +
> >  4.2 Task migration
> >  
> >  When a task migrates from one cgroup to another, it's charge is not
> > @@ -271,16 +329,19 @@ carried forward by default. The pages al
> >  remain charged to it, the charge is dropped when the page is freed or
> >  reclaimed.
> >  
> > -Note: You can move charges of a task along with task migration. See 8.
> > +You can move charges of a task along with task migration.
> > +See 8. "Move charges at task migration"
> >  
> >  4.3 Removing a cgroup
> >  
> >  A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
> >  cgroup might have some charge associated with it, even though all
> > -tasks have migrated away from it.
> > -Such charges are freed(at default) or moved to its parent. When moved,
> > -both of RSS and CACHES are moved to parent.
> > -If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also.
> > +tasks have migrated away from it. (because we charge against pages, not
> > +against tasks.)
> > +
> > +Such charges are freed or moved to its parent. At moving, both of RSS
> 
>                                       their
> 
will fix.

> > +and CACHES are moved to parent.
> > +rmdir() may return -EBUSY if freeing/moving fails. See 5.1 Also.
> 
>                                                               also.
> 

will fix.

> >  
> >  Charges recorded in swap information is not updated at removal of cgroup.
> >  Recorded information is discarded and a cgroup which uses swap (swapcache)
> > @@ -309,19 +370,41 @@ will be charged as a new owner of it.
> >  
> >  memory.stat file includes following statistics
> >  
> > +# per-memcg local status
> >  cache		- # of bytes of page cache memory.
> >  rss		- # of bytes of anonymous and swap cache memory.
> > +mapped_file	- # of bytes of mapped file (includes tmpfs/shmem)
> >  pgpgin		- # of pages paged in (equivalent to # of charging events).
> >  pgpgout		- # of pages paged out (equivalent to # of uncharging events).
> > -active_anon	- # of bytes of anonymous and  swap cache memory on active
> > -		  lru list.
> > +swap		- # of bytes of swap usage
> >  inactive_anon	- # of bytes of anonymous memory and swap cache memory on
> > +		  lru list.
> > +active_anon	- # of bytes of anonymous and  swap cache memory on active
> >  		  inactive lru list.
> > -active_file	- # of bytes of file-backed memory on active lru list.
> >  inactive_file	- # of bytes of file-backed memory on inactive lru list.
> > +active_file	- # of bytes of file-backed memory on active lru list.
> >  unevictable	- # of bytes of memory that cannot be reclaimed (mlocked etc).
> >  
> > -The following additional stats are dependent on CONFIG_DEBUG_VM.
> > +# status considering hierarchy (see memory.use_hierarchy settings)
> > +
> > +hierarchical_memory_limit - # of bytes of memory limit with regard to hierarchy
> > +			under which the memcg is
> > +hierarchical_memsw_limit - # of bytes of memory+swap limit with regard to
> > +			hierarchy under which memcg is.
> > +
> > +total_cache		- sum of all children's "cache"
> > +total_rss		- sum of all children's "rss"
> > +total_mapped_file	- sum of all children's "cache"
> > +total_pgpgin		- sum of all children's "pgpgin"
> > +total_pgpgout		- sum of all children's "pgpgout"
> > +total_swap		- sum of all children's "swap"
> > +total_inactive_anon	- sum of all children's "inactive_anon"
> > +total_active_anon	- sum of all children's "active_anon"
> > +total_inactive_file	- sum of all children's "inactive_file"
> > +total_active_file	- sum of all children's "active_file"
> > +total_unevictable	- sum of all children's "unevictable"
> > +
> > +# The following additional stats are dependent on CONFIG_DEBUG_VM.
> >  
> >  inactive_ratio		- VM internal parameter. (see mm/page_alloc.c)
> >  recent_rotated_anon	- VM internal parameter. (see mm/vmscan.c)
> > @@ -337,17 +420,25 @@ Memo:
> >  Note:
> >  	Only anonymous and swap cache memory is listed as part of 'rss' stat.
> >  	This should not be confused with the true 'resident set size' or the
> > -	amount of physical memory used by the cgroup. Per-cgroup rss
> > -	accounting is not done yet.
> > +	amount of physical memory used by the cgroup.
> > +	'rss + file_mapped" will give you resident set size of cgroup.
> > +	(Note: file and shmem may be shared amoung other cgroups. In that case,
> > +	 file_mapped is accounted only when the memcg is owner of page cache.)
> >  
> >  5.3 swappiness
> >    Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
> >  
> >    Following cgroups' swappiness can't be changed.
> >    - root cgroup (uses /proc/sys/vm/swappiness).
> > -  - a cgroup which uses hierarchy and it has child cgroup.
> > +  - a cgroup which uses hierarchy and it has other cgroup(s) below it.
> >    - a cgroup which uses hierarchy and not the root of hierarchy.
> >  
> > +5.4 failcnt
> > +
> > +The memory controller provides memory.failcnt and memory.memsw.failcnt files.
> > +This failcnt(== failure count) shows the number of events that usage counter
> 
>                                   shows the number of times that a usage counter
> 
Ah. will fix.

> > +hit limits. When a memory controller hit limit, failcnt increase and memory
> 
>    hit its limit. When a memory controller hits a limit, failcnt increases and memory
> 

Thank you.
-Kame

> > +under it will be reclaimed.
> >  
> >  6. Hierarchy support
> >  
> 
> 
> HTH.
> 
> ---
> ~Randy

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