linux-kernel - Re: MADV_DONTNEED semantics? Was: [RFC PATCH] mm: madvise: Ignore repeated MADV

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Message-ID: <54D87A23.40703@gmail.com>
Date:	Mon, 09 Feb 2015 10:13:07 +0100
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Minchan Kim <minchan@...nel.org>
CC:	mtk.manpages@...il.com, Vlastimil Babka <vbabka@...e.cz>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Dave Hansen <dave.hansen@...el.com>,
	Mel Gorman <mgorman@...e.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	linux-man <linux-man@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: MADV_DONTNEED semantics? Was: [RFC PATCH] mm: madvise: Ignore
 repeated MADV_DONTNEED hints

Hello Minchan

On 02/09/2015 07:46 AM, Minchan Kim wrote:
> Hello, Michael
> 
> On Fri, Feb 06, 2015 at 04:41:12PM +0100, Michael Kerrisk (man-pages) wrote:
>> On 02/05/2015 02:07 AM, Minchan Kim wrote:
>>> Hello,
>>>
>>> On Wed, Feb 04, 2015 at 08:24:27PM +0100, Michael Kerrisk (man-pages) wrote:
>>>> On 4 February 2015 at 18:02, Vlastimil Babka <vbabka@...e.cz> wrote:
>>>>> On 02/04/2015 03:00 PM, Michael Kerrisk (man-pages) wrote:

[...]

>>> And we should make error section, too.
>>> "locked" covers mlock(2) and you said you will add hugetlb. Then,
>>> VM_PFNMAP? In that case, it fails. How can we say about VM_PFNMAP?
>>> special mapping for some drivers?
>>
>> I'm open for offers on what to add.
> 
> I suggests from quote "LWN" http://lwn.net/Articles/162860/
> "*special mapping* which is not made up of "normal" pages.
> It is usually created by device drivers which map special memory areas
> into user space"

Thanks. I've added mention of VM_PFNMAP in the discussion of both 
MADV_DONTNEED and MADV_REMOVE, and noted that both of those
operations will give an error when applied to VM_PFNMAP pages.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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