On Fri, Nov 11, 2011 at 4:20 PM, Dave Hylands <dhylands@gmail.com> wrote:

Hi Geraint,

On Thu, Nov 10, 2011 at 8:44 PM, Geraint Yang <geraint0923@gmail.com> wrote:
> Hi Dave,
> Thank you for your help !
> Does it mean that I could use all of the memory my computer has? But one of
> my classmates told me that kernel could only use 1G from a 4G
> memory.computer...Is there anything I have misunderstood ?

There is a certain amount (exact amount depends on the architecture
and configuration) that can be accessed directly all of the time.

Then there is high memory, which can be accessed using kmap/kunmap.
See http://linux-mm.org/HighMemory

If you have a 64-bit system, then you can access all of the memory directly.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com