[PATCH] memcg: update document to mention swapoff should be test.

[PATCH] memcg: update document to mention swapoff should be test.

[KAMEZAWA Hiroyuki]

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Considering recently found problem:
 memcg-fix-refcnt-handling-at-swapoff.patch

It's better to mention about swapoff behavior in memcg_test document.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 Documentation/cgroups/memcg_test.txt |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

Index: mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
===================================================================
--- mmotm-2.6.29-Jan16.orig/Documentation/cgroups/memcg_test.txt
+++ mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
@@ -1,6 +1,6 @@
 Memory Resource Controller(Memcg)  Implementation Memo.
-Last Updated: 2008/12/15
-Base Kernel Version: based on 2.6.28-rc8-mm.
+Last Updated: 2009/1/19
+Base Kernel Version: based on 2.6.29-rc2.
 
 Because VM is getting complex (one of reasons is memcg...), memcg's behavior
 is complex. This is a document for memcg's internal behavior.
@@ -340,3 +340,23 @@ Under below explanation, we assume CONFI
 	# mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
 
 	and do task move, mkdir, rmdir etc...under this.
+
+ 9.7 swapoff.
+	Besides management of swap is one of complicated parts of memcg,
+	call path of swap-in at swapoff is not same as usual swap-in path..
+	It's worth to be tested explicitly.
+
+	For example, test like following is good.
+	(Shell-A)
+	# mount -t cgroup none /cgroup -t memory
+	# mkdir /cgroup/test
+	# echo 40M > /cgroup/test/memory.limit_in_bytes
+	# echo 0 > /cgroup/test/tasks
+	Run malloc(100M) program under this. You'll see 60M of swaps.
+	(Shell-B)
+	# move all tasks in /cgroup/test to /cgroup
+	# /sbin/swapoff -a
+	# rmdir /test/cgroup
+	# kill malloc task.
+
+	Of course, tmpfs v.s. swapoff test should be tested, too.

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Re: [PATCH] memcg: update document to mention swapoff should be test.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-19 15:57:48]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Considering recently found problem:
>  memcg-fix-refcnt-handling-at-swapoff.patch
> 
> It's better to mention about swapoff behavior in memcg_test document.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  Documentation/cgroups/memcg_test.txt |   24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 
> Index: mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> ===================================================================
> --- mmotm-2.6.29-Jan16.orig/Documentation/cgroups/memcg_test.txt
> +++ mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> @@ -1,6 +1,6 @@
>  Memory Resource Controller(Memcg)  Implementation Memo.
> -Last Updated: 2008/12/15
> -Base Kernel Version: based on 2.6.28-rc8-mm.
> +Last Updated: 2009/1/19
> +Base Kernel Version: based on 2.6.29-rc2.
> 
>  Because VM is getting complex (one of reasons is memcg...), memcg's behavior
>  is complex. This is a document for memcg's internal behavior.
> @@ -340,3 +340,23 @@ Under below explanation, we assume CONFI
>  	# mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
> 
>  	and do task move, mkdir, rmdir etc...under this.
> +
> + 9.7 swapoff.
> +	Besides management of swap is one of complicated parts of memcg,
> +	call path of swap-in at swapoff is not same as usual swap-in path..
> +	It's worth to be tested explicitly.
> +
> +	For example, test like following is good.
> +	(Shell-A)
> +	# mount -t cgroup none /cgroup -t memory
> +	# mkdir /cgroup/test
> +	# echo 40M > /cgroup/test/memory.limit_in_bytes
> +	# echo 0 > /cgroup/test/tasks

0? shouldn't this be pid? Potentially echo $$

> +	Run malloc(100M) program under this. You'll see 60M of swaps.
> +	(Shell-B)
> +	# move all tasks in /cgroup/test to /cgroup
> +	# /sbin/swapoff -a
> +	# rmdir /test/cgroup
> +	# kill malloc task.
> +
> +	Of course, tmpfs v.s. swapoff test should be tested, too.
>


-- 
	Balbir

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Re: [PATCH] memcg: update document to mention swapoff should be test.

[KAMEZAWA Hiroyuki]

On Mon, 19 Jan 2009 12:42:20 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-19 15:57:48]:
> 
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > Considering recently found problem:
> >  memcg-fix-refcnt-handling-at-swapoff.patch
> > 
> > It's better to mention about swapoff behavior in memcg_test document.
> > 
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  Documentation/cgroups/memcg_test.txt |   24 ++++++++++++++++++++++--
> >  1 file changed, 22 insertions(+), 2 deletions(-)
> > 
> > Index: mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> > ===================================================================
> > --- mmotm-2.6.29-Jan16.orig/Documentation/cgroups/memcg_test.txt
> > +++ mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> > @@ -1,6 +1,6 @@
> >  Memory Resource Controller(Memcg)  Implementation Memo.
> > -Last Updated: 2008/12/15
> > -Base Kernel Version: based on 2.6.28-rc8-mm.
> > +Last Updated: 2009/1/19
> > +Base Kernel Version: based on 2.6.29-rc2.
> > 
> >  Because VM is getting complex (one of reasons is memcg...), memcg's behavior
> >  is complex. This is a document for memcg's internal behavior.
> > @@ -340,3 +340,23 @@ Under below explanation, we assume CONFI
> >  	# mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
> > 
> >  	and do task move, mkdir, rmdir etc...under this.
> > +
> > + 9.7 swapoff.
> > +	Besides management of swap is one of complicated parts of memcg,
> > +	call path of swap-in at swapoff is not same as usual swap-in path..
> > +	It's worth to be tested explicitly.
> > +
> > +	For example, test like following is good.
> > +	(Shell-A)
> > +	# mount -t cgroup none /cgroup -t memory
> > +	# mkdir /cgroup/test
> > +	# echo 40M > /cgroup/test/memory.limit_in_bytes
> > +	# echo 0 > /cgroup/test/tasks
> 
> 0? shouldn't this be pid? Potentially echo $$
> 

0 is handled as $$ in cgroup/tasks file.

-Kame

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Re: [PATCH] memcg: update document to mention swapoff should be test.

[Balbir Singh]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-19 16:15:08]:

> On Mon, 19 Jan 2009 12:42:20 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-19 15:57:48]:
> > 
> > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > 
> > > Considering recently found problem:
> > >  memcg-fix-refcnt-handling-at-swapoff.patch
> > > 
> > > It's better to mention about swapoff behavior in memcg_test document.
> > > 
> > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > > ---
> > >  Documentation/cgroups/memcg_test.txt |   24 ++++++++++++++++++++++--
> > >  1 file changed, 22 insertions(+), 2 deletions(-)
> > > 
> > > Index: mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> > > ===================================================================
> > > --- mmotm-2.6.29-Jan16.orig/Documentation/cgroups/memcg_test.txt
> > > +++ mmotm-2.6.29-Jan16/Documentation/cgroups/memcg_test.txt
> > > @@ -1,6 +1,6 @@
> > >  Memory Resource Controller(Memcg)  Implementation Memo.
> > > -Last Updated: 2008/12/15
> > > -Base Kernel Version: based on 2.6.28-rc8-mm.
> > > +Last Updated: 2009/1/19
> > > +Base Kernel Version: based on 2.6.29-rc2.
> > > 
> > >  Because VM is getting complex (one of reasons is memcg...), memcg's behavior
> > >  is complex. This is a document for memcg's internal behavior.
> > > @@ -340,3 +340,23 @@ Under below explanation, we assume CONFI
> > >  	# mount -t cgroup none /cgroup -t cpuset,memory,cpu,devices
> > > 
> > >  	and do task move, mkdir, rmdir etc...under this.
> > > +
> > > + 9.7 swapoff.
> > > +	Besides management of swap is one of complicated parts of memcg,
> > > +	call path of swap-in at swapoff is not same as usual swap-in path..
> > > +	It's worth to be tested explicitly.
> > > +
> > > +	For example, test like following is good.
> > > +	(Shell-A)
> > > +	# mount -t cgroup none /cgroup -t memory
> > > +	# mkdir /cgroup/test
> > > +	# echo 40M > /cgroup/test/memory.limit_in_bytes
> > > +	# echo 0 > /cgroup/test/tasks
> > 
> > 0? shouldn't this be pid? Potentially echo $$
> > 
> 
> 0 is handled as $$ in cgroup/tasks file.
>

OK, I remember having the 0 discussion for cgroups. Thanks for
clarifying. The test looks good, 0 is a bit confusing, since it is a
valid pid not visible to user space... but that is already done and
closed. Hence,

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> 

-- 
	Balbir

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