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

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Date:	Mon, 4 Mar 2013 20:21:25 +0800
From:	Lenky Gao <lenky.gao@...il.com>
To:	Zlatko Calusic <zlatko.calusic@...on.hr>
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?

2013/3/4 Zlatko Calusic <zlatko.calusic@...on.hr>:
>
> 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

Thanks for your advice.

The inactive memory still cannot be reclaimed after i execute the sync command:

# cat /proc/meminfo | grep Inactive\(file\);
Inactive(file):   882824 kB
# sync;
# echo 3 > /proc/sys/vm/drop_caches
# cat /proc/meminfo | grep Inactive\(file\);
Inactive(file):   777664 kB

I find these page becomes orphaned in this function, but do not understand why:

/*
 * If truncate cannot remove the fs-private metadata from the page, the page
 * becomes orphaned.  It will be left on the LRU and may even be mapped into
 * user pagetables if we're racing with filemap_fault().
 *
 * We need to bale out if page->mapping is no longer equal to the original
 * mapping.  This happens a) when the VM reclaimed the page while we waited on
 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
 */
static int
truncate_complete_page(struct address_space *mapping, struct page *page)
{
...

My file system type is ext3, mounted with the opteion data=journal and
it is easy to reproduce.

-- 
Regards,

Lenky
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