From: Wanpeng Li <liwanp@linux.vnet.ibm.com>
To: Simon Jeons <simon.jeons@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>, 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()
Date: Thu, 21 Mar 2013 16:59:24 +0800 [thread overview]
Message-ID: <20130321085924.GA13665@hacker.(null)> (raw)
In-Reply-To: <514AC583.2090909@gmail.com>
On Thu, Mar 21, 2013 at 04:32:03PM +0800, Simon Jeons wrote:
>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?
who prefer direct IO:
- the users believe they can manage caching of file contents better than
the kernel can.
- the users want to avoid overflowing the page cache with data which is
unlikely to be of use in the near future.
Regards,
Wanpeng Li
>
>
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next prev parent reply other threads:[~2013-03-21 8:59 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-20 18:19 [PATCH] mm: page_alloc: Avoid marking zones full prematurely after zone_reclaim() Mel Gorman
2013-03-20 18:45 ` Michal Hocko
2013-03-21 2:32 ` Wanpeng Li
2013-03-21 2:32 ` Wanpeng Li
2013-03-21 2:33 ` Simon Jeons
2013-03-21 8:19 ` Michal Hocko
2013-03-21 8:32 ` Simon Jeons
2013-03-21 8:44 ` Michal Hocko
2013-03-21 8:59 ` Wanpeng Li [this message]
2013-03-21 8:59 ` Wanpeng Li
2013-04-05 6:31 ` Simon Jeons
2013-04-07 6:37 ` Simon Jeons
2013-04-09 10:05 ` Simon Jeons
2013-04-09 10:14 ` Michal Hocko
2013-04-09 10:20 ` Simon Jeons
2013-04-10 5:15 ` Ric Mason
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