linux-kernel - Re: Mapping memory between kernel and user space

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Message-ID: <20110216050941.GB28895@in.ibm.com>
Date:	Wed, 16 Feb 2011 10:39:41 +0530
From:	Ankita Garg <ankita@...ibm.com>
To:	Sri Ram Vemulpali <sri.ram.gmu06@...il.com>
Cc:	Kernel-newbies <kernelnewbies@...linux.org>,
	linux-kernel-mail <linux-kernel@...r.kernel.org>
Subject: Re: Mapping memory between kernel and user space

Hi,

On Tue, Feb 15, 2011 at 12:15:08PM -0500, Sri Ram Vemulpali wrote:
> As was suggested I started reading chap 15v from LDD. I ran more into
> confusion state.
> 
> I know that virtual address(process space), linear address
> (segmentation) and physical address. And how are they resolved from
> virtual to physical.
> But coming to kernel they distinguish logical address from virtual
> address. What is the main difference.
> Also, they emphasize on high memory and low memory. Why can not high
> memory can be mapped in to kernel completely.
> Why is that kernel has less visibility of complete space available on RAM.
> Linux MM is it a very specific implementation of linux, or Is that a
> traditional implementation.
> 

You may want to go through the literature available on the VM subsystem.
Especially, Mel Gorman's book:

http://ptgmedia.pearsoncmg.com/images/0131453483/downloads/gorman_book.pdf

> what is very minimal implementation of MMU for real time systems.
>

Linux VM subsystem for the RT kernel is not different from traditional
one. The application has to ensure that it pins/locks its pages during
execution.
 
> Thanks in advance.
> 
> --Sri.
> 
> On Tue, Feb 15, 2011 at 12:54 AM, Ankita Garg <ankita@...ibm.com> wrote:
> > On Wed, Feb 09, 2011 at 06:45:42PM -0500, Sri Ram Vemulpali wrote:
> >> Hi all,
> >>
> >>   How do I map some space between kernel and user space. Can anyone
> >> point me in to right direction. I was trying to map the packets from
> >> my netfilter function to kernel user space, to avoid over head of
> >> copying. Thanks in advance.
> >>
> >
> > You can take a look at remap_pfn_range() routine when implementing mmap
> > in your driver.
> >
> > --
> > Regards,
> > Ankita Garg (ankita@...ibm.com)
> > Linux Technology Center
> > IBM India Systems & Technology Labs,
> > Bangalore, India
> >
> 
> 
> 
> -- 
> Regards,
> Sri.

-- 
Regards,
Ankita Garg (ankita@...ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs,
Bangalore, India
--
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