linux-kernel - Re: About cgroup memory limits

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Message-ID: <4FAB8EB5.8080901@jp.fujitsu.com>
Date:	Thu, 10 May 2012 18:47:33 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andre Nathan <andre@...irati.com.br>
CC:	linux-kernel@...r.kernel.org, balbir@...ux.vnet.ibm.com
Subject: Re: About cgroup memory limits

(2012/05/10 3:37), Andre Nathan wrote:

> Hello
> 
> I'm doing some tests with LXC and how it interacts with the memory
> cgroup limits, more specifically the memory.limit_in_bytes control file.
> 
> Am I correct in my understanding of the memory cgroup documentation[1]
> that the limit set in memory.limit_in_bytes is applied to the sum of the
> fields 'cache', 'rss' and 'mapped_file' in the memory.stat file?
> 

cache includes mapped_file. Then,

rss + cache < limit.

cache - mapped_file == unmapped file caches.


> I am also trying to understand the values reported in memory.stat when
> compared to the statistics in /proc/$PID/statm.
> 
> Below is the sum of each field in /proc/$PID/statm for every process
> running inside a test container, converted to bytes:
> 
>        size  resident     share     text  lib       data  dt
>   897208320  28741632  20500480  1171456    0  170676224   0
> 

from statm source code.

size      = total virtual memory size
            # total amount of mmaps().

shared    = mapped_file
            # resident mapped file caches

text      = end_code - start_code
            # end_code and start_code is determined when the program is loaded.
            # this is virtual memory size.

data      = total virtual memory size  - MAP_SHARED virtual memory size.

regisdent = anonymous pages + mapped_file.


> Compare this with the usage reports from memory.stat (fields total_*,
> hierarchical_* and pg* omitted):
> 
> cache                     16834560
> rss                       8192000
> mapped_file               3743744
> swap                      0
> inactive_anon             0
> active_anon               8192000
> inactive_file             13996032
> active_file               2838528
> unevictable               0
> 
> Is there a way to reconcile these numbers somehow? I understand that the
> fields from the two files represent different things. What I'm trying to
> do is to combine, for example, the fields from memory.stat to
> approximately reach what is displayed by statm.
> 


>From above, rss + mapped_file == resident.

Thanks,
-Kame


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