Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S933099Ab0BPQ7F (ORCPT <rfc822;w@1wt.eu>);
	Tue, 16 Feb 2010 11:59:05 -0500
Received: from zcars04e.nortel.com ([47.129.242.56]:50849 "EHLO
	zcars04e.nortel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932797Ab0BPQ7D (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 16 Feb 2010 11:59:03 -0500
Message-ID: <4B7ACD4A.10101@nortel.com>
Date: Tue, 16 Feb 2010 10:52:26 -0600
From: "Chris Friesen" <cfriesen@nortel.com>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100120 Fedora/3.0.1-1.fc11 Thunderbird/3.0.1
MIME-Version: 1.0
To: Rik van Riel <riel@redhat.com>
CC: Minchan Kim <minchan.kim@gmail.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-mm@kvack.org, Balbir Singh <balbir@linux.vnet.ibm.com>
Subject: Re: tracking memory usage/leak in "inactive" field in /proc/meminfo?
References: <4B71927D.6030607@nortel.com>	 <20100210093140.12D9.A69D9226@jp.fujitsu.com>	 <4B72E74C.9040001@nortel.com>	 <28c262361002101645g3fd08cc7t6a72d27b1f94db62@mail.gmail.com>	 <4B74524D.8080804@nortel.com> <28c262361002111838q7db763feh851a9bea4fdd9096@mail.gmail.com> <4B7504D2.1040903@nortel.com> <4B796D31.7030006@nortel.com> <4B797D93.5090307@redhat.com>
In-Reply-To: <4B797D93.5090307@redhat.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-OriginalArrivalTime: 16 Feb 2010 16:58:54.0321 (UTC) FILETIME=[52539610:01CAAF29]
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1974
Lines: 57

On 02/15/2010 11:00 AM, Rik van Riel wrote:
> On 02/15/2010 10:50 AM, Chris Friesen wrote:
> 
>> Looking at the code, it looks like page_remove_rmap() clears the
>> Anonpage flag and removes it from NR_ANON_PAGES, and the caller is
>> responsible for removing it from the LRU.  Is that right?
> 
> Nope.
> 
>> I'll keep digging in the code, but does anyone know where the removal
>> from the LRU is supposed to happen in the above code paths?
> 
> Removal from the LRU is done from the page freeing code, on
> the final free of the page.
> 
> It appears you have code somewhere that increments the reference
> count on user pages and then forgets to lower it afterwards.

Okay, that makes sense.

I'm still trying to get a handle on the LRU removal though.  The code
path that I saw most which resulted in clearing the anon bit but leaving
the page on the LRU was the following:


    [<ffffffff8029c951>] kmemleak_clear_anon+0x7f/0xbe
    [<ffffffff802864c7>] page_remove_rmap+0x45/0x146
    [<ffffffff8027dc7e>] unmap_vmas+0x41c/0x948
    [<ffffffff80282405>] exit_mmap+0x7b/0x108
    [<ffffffff8022f441>] mmput+0x33/0x110
    [<ffffffff80233b05>] exit_mm+0x103/0x130
    [<ffffffff802355b5>] do_exit+0x17b/0x91f
    [<ffffffff80235d95>] do_group_exit+0x3c/0x9c
    [<ffffffff80235e07>] sys_exit+0x0/0x12
    [<ffffffff8021ddb5>] ia32_syscall_done+0x0/0xa

There are a bunch of inline functions involved, but I think the chain
from page_remove_rmap() back up to unmap_vmas() looks like this:

page_remove_rmap
zap_pte_range
zap_pmd_range
zap_pud_range
unmap_page_range
unmap_vmas

So in this scenario, where do the pages actually get removed from the
LRU list (assuming that they're not in use by anyone else)?

Thanks,

Chris
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/