linux-kernel - Re: [PATCH] memcg: Fix documentation

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Date:	Wed, 8 Apr 2009 14:03:27 +0530
From:	Bharata B Rao <bharata@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] memcg: Fix documentation

On Wed, Apr 08, 2009 at 04:25:28PM +0900, KAMEZAWA Hiroyuki wrote:
> Thank you, very helpful. but some nitpicks.
> 
> 
> On Wed, 8 Apr 2009 12:48:17 +0530
> Bharata B Rao <bharata@...ux.vnet.ibm.com> wrote:
> 
> > memcg: Fix documentation.
> > 
> > The description about various statistics from memory.stat is not accurate
> > and confusing at times.
> > 
> > Correct this along with a few other minor cleanups.
> > 
> > Signed-off-by: Bharata B Rao <bharata@...ux.vnet.ibm.com>
> > Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>
> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> >  Documentation/cgroups/memory.txt |   50 +++++++++++++++++++++------------------
> >  1 file changed, 28 insertions(+), 22 deletions(-)
> > 
> > --- a/Documentation/cgroups/memory.txt
> > +++ b/Documentation/cgroups/memory.txt
> > @@ -6,15 +6,14 @@ used here with the memory controller tha
> >  
> >  Salient features
> >  
> > -a. Enable control of both RSS (mapped) and Page Cache (unmapped) pages
> > +a. Enable control of RSS (mapped), Page Cache (unmapped) and Swap cache
> > +   (unmapped) pages.
>       Enable control of Anonymous memory, Page Cache and Swap Cache. 
> ?

I feel without the terms 'mapped' and 'unmaapped', the story of the memory
controller is not complete :)

> 
> >  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
> >  
> > -NOTE: Swap Cache (unmapped) is not accounted now.
> > -
> >  Benefits and Purpose of the memory controller
> >  
> >  The memory controller isolates the memory behaviour of a group of tasks
> > @@ -290,34 +289,41 @@ will be charged as a new owner of it.
> >    moved to the parent. If you want to avoid that, force_empty will be useful.
> >  
> >  5.2 stat file
> > -  memory.stat file includes following statistics (now)
> > -	cache			- # of pages from page-cache and shmem.
> > -	rss			- # of pages from anonymous memory.
> > -	pgpgin			- # of event of charging
> > -	pgpgout			- # of event of uncharging
> > -	active_anon		- # of pages on active lru of anon, shmem.
> > -	inactive_anon 		- # of pages on active lru of anon, shmem
> > -	active_file		- # of pages on active lru of file-cache
> > -	inactive_file		- # of pages on inactive lru of file cache
> > -	unevictable		- # of pages cannot be reclaimed.(mlocked etc)
> > -
> > -	Below is depend on CONFIG_DEBUG_VM.
> > -	inactive_ratio		- VM inernal parameter. (see mm/page_alloc.c)
> > -	recent_rotated_anon	- VM internal parameter. (see mm/vmscan.c)
> > -	recent_rotated_file	- VM internal parameter. (see mm/vmscan.c)
> > -	recent_scanned_anon 	- VM internal parameter. (see mm/vmscan.c)
> > -	recent_scanned_file 	- VM internal parameter. (see mm/vmscan.c)
> >  
> > -  Memo:
> > +memory.stat file includes following statistics
> > +
> > +cache		- # of bytes of page-cache memory.
> > +rss		- # of bytes of anonymous memory.
>                     This includes # of swap cache.

Ok, will add that.

> 
> > +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 memory on active lru list.
>                                 anonymous memory + shared memory(tmpfs) + SwapCache.

Ok.

>                           Seeing acitive/inactive_file, how about swap-backed memory ?

Not sure what you are hinting at here.

Will post a new patch with the above changes. Thanks for your review.

Regards,
Bharata.
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