From: Michal Hocko <mhocko@suse.cz>
To: Simon Jeons <simon.jeons@gmail.com>
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()
Date: Thu, 21 Mar 2013 09:44:41 +0100 [thread overview]
Message-ID: <20130321084441.GE6094@dhcp22.suse.cz> (raw)
In-Reply-To: <514AC583.2090909@gmail.com>
On Thu 21-03-13 16:32:03, 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.
This is getting off-topic.
> dd will use page cache instead of direct IO?
no by default. You can use direct option. Refer to man dd for more
information.
> Where can I got dd source codes?
dd is part of coreutils: http://www.gnu.org/software/coreutils/
Please do not be afraid to use google. Most of these answers are there
already...
> One offline question, when should use page cache and when should use
> direct IO?
And this is really off-topic. The simplest answer would be. Use direct
IO when you want to prevent from caching because you are doing it
yourselvef. Please try to search the web it is full of more specific
examples.
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-03-21 8:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-20 18:19 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 [this message]
2013-03-21 8:59 ` Wanpeng Li
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130321084441.GE6094@dhcp22.suse.cz \
--to=mhocko@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=hedi@sgi.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=simon.jeons@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox