linux-kernel - Re: Inactive memory keep growing and how to release it?

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Message-ID: <51347A6E.8010608@iskon.hr>
Date:	Mon, 04 Mar 2013 11:41:50 +0100
From:	Zlatko Calusic <zlatko.calusic@...on.hr>
To:	Lenky Gao <lenky.gao@...il.com>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: Inactive memory keep growing and how to release it?

On 04.03.2013 10:52, Lenky Gao wrote:
> Hi,
>
> When i just run a test on Centos 6.2 as follows:
>
> #!/bin/bash
>
> while true
> do
>
> 	file="/tmp/filetest"
>
> 	echo $file
>
> 	dd if=/dev/zero of=${file} bs=512 count=204800 &> /dev/null
>
> 	sleep 5
> done
>
> the inactive memory keep growing:
>
> #cat /proc/meminfo | grep Inactive\(fi
> Inactive(file):   420144 kB
> ...
> #cat /proc/meminfo | grep Inactive\(fi
> Inactive(file):   911912 kB
> ...
> #cat /proc/meminfo | grep Inactive\(fi
> Inactive(file):  1547484 kB
> ...
>
> and i cannot reclaim it:
>
> # cat /proc/meminfo | grep Inactive\(fi
> Inactive(file):  1557684 kB
> # echo 3 > /proc/sys/vm/drop_caches
> # cat /proc/meminfo | grep Inactive\(fi
> Inactive(file):  1520832 kB
>
> I have tested on other version kernel, such as 2.6.30 and .6.11, the
> problom also exists.
>
> When in the final situation, i cannot kmalloc a larger contiguous
> memory, especially in interrupt context.
> Can you give some tips to avoid this?
>

The drop_caches mechanism doesn't free dirty page cache pages. And your 
bash script is creating a lot of dirty pages. Run it like this and see 
if it helps your case:

sync; echo 3 > /proc/sys/vm/drop_caches

Regards,
-- 
Zlatko
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