linux-kernel - Re: mmap hw behavior

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Message-ID: <4A54DF6F.1010405@petalogix.com>
Date:	Wed, 08 Jul 2009 20:03:27 +0200
From:	Michal Simek <michal.simek@...alogix.com>
To:	David Miller <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	mingo@...e.hu, arnd@...db.de, lethal@...ux-sh.org,
	ltp-list@...ts.sourceforge.net
Subject: Re: mmap hw behavior

David Miller wrote:
> From: Michal Simek <michal.simek@...alogix.com>
> Date: Wed, 08 Jul 2009 19:03:11 +0200
>
>   
>> When I call mmap for that open file with pointer to calloc place
>> (first parameter, + length zero) it should be one tlb invalidation
>> for calloc and new tlb which connect open file.  We check it and we
>> don't have any tlb invalidation that's why I think that kernel do
>> different thigs.  Or is it there any copying? Or anything different?
>>     
>
> There is no need to tlb flush the calloc area unless that memory area
> is actually touched by the user application and thus the page is
> faulted in.
>   
That calloc area is filled by any value (in that test). Is it mean that
for this case when calloc area is touched
there must be tlb invalidation + remapping?

Michal


-- 
Michal Simek, Ing. (M.Eng)
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com p: +61-7-30090663,+42-0-721842854 f: +61-7-30090663

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