Message-ID: <514AC583.2090909@gmail.com>
Date: Thu, 21 Mar 2013 16:32:03 +0800
From: Simon Jeons <simon.jeons@gmail.com>
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130308 Thunderbird/17.0.4
MIME-Version: 1.0
To: Michal Hocko <mhocko@suse.cz>
CC: Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>,
        Hedi Berriche <hedi@sgi.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: page_alloc: Avoid marking zones full prematurely
 after zone_reclaim()
References: <20130320181957.GA1878@suse.de> <514A7163.5070700@gmail.com> <20130321081902.GD6094@dhcp22.suse.cz>
In-Reply-To: <20130321081902.GD6094@dhcp22.suse.cz>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1262
Lines: 29

Hi Michal,
On 03/21/2013 04:19 PM, Michal Hocko wrote:
> On Thu 21-03-13 10:33:07, Simon Jeons wrote:
>> Hi Mel,
>> On 03/21/2013 02:19 AM, Mel Gorman wrote:
>>> The following problem was reported against a distribution kernel when
>>> zone_reclaim was enabled but the same problem applies to the mainline
>>> kernel. The reproduction case was as follows
>>>
>>> 1. Run numactl -m +0 dd if=largefile of=/dev/null
>>>     This allocates a large number of clean pages in node 0
>> I confuse why this need allocate a large number of clean pages?
> It reads from file and puts pages into the page cache. The pages are not
> modified so they are clean. Output file is /dev/null so no pages are
> written. dd doesn't call fadvise(POSIX_FADV_DONTNEED) on the input file
> by default so pages from the file stay in the page cache

Thanks for your clarify Michal.
dd will use page cache instead of direct IO? Where can I got dd source 
codes?
One offline question, when should use page cache and when should use 
direct IO?


--
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/