linux-kernel - Re: Kernel vs user memory

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Message-ID: <21513615.post@talk.nabble.com>
Date:	Fri, 16 Jan 2009 22:34:27 -0800 (PST)
From:	sidc7 <siddhartha.chhabra@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Kernel vs user memory


If I am not mistaken, Linux kernel is a high memory kernel, hence for Linux
kernel, nothing will be mapped to the kernel space, other than the memory
beyond 896MB which is the kernel's virtual address space. Am I right on
this?

Thanks


H. Peter Anvin wrote:
> 
> sidc7 wrote:
>> The kernel maintains a free list of pages that are free in physical
>> memory. I
>> was wondering, are these pages in the kernel space ? They are not mapped
>> to
>> any of the user address space for sure, so will they be in the kernel
>> memory
>> ?
> 
> On a non-highmem kernel, they will be -- ALL memory is mapped in kernel
> space on non-highmem kernels.  For highmem kernels, they will generally
> not be mapped at all, unless they are lowmem pages.
> 
> 	-hpa
> 
> -- 
> H. Peter Anvin, Intel Open Source Technology Center
> I work for Intel.  I don't speak on their behalf.
> 
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