Re: A quick question on VM

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On Jan 11, 2008 10:57 AM, sahlot arvind <asahlot@xxxxxxxxx> wrote:
Hi All,
 
I just started learning Linux Virtual Memory Management Subsystem.
I see the memory is divided into three zones. Comments in file mm/mmzone.h
 
/*
 * ZONE_DMA       < 16 MB       ISA DMA capable memory
 * ZONE_NORMAL  16-896 MB       direct mapped by the kernel
 * ZONE_HIGHMEM  > 896 MB       only page cache and user processes
 */
 
Here second comment (ZONE_NORMAL) says that it is directly mapped by kernel.
Could anybody please tell me what does direct mean here?
Does this mean Physical address = Virtual Address???

yes, thats right.
This means any virtual address can be translated to the physical address by simply subtracting PAGE_OFFSET at 3GB on x86, which is essentially what the function virt_to_phys() with the macro __pa() does.

 
 
 
Thanks
 - Arvind



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Thanks & Regards,
Mahaveer Darade
mah.darade@xxxxxxxxx
Mobile - 9970365267


--- Dream it , Code it.

---The "silly question" is the first intimation of some totally new development

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