[Gllug] 4G Memory Restriction

Steve Nelson sanelson at gmail.com
Mon Apr 10 10:24:50 UTC 2006


On 4/10/06, Alain Williams <addw at phcomp.co.uk> wrote:
> 4GB is the max that can be addressed with 32 bits, however by fiddling with
> the address tables you can make use of more than 4GB.

Is this the PAE stuff? This allows a  total of 64G of ram to be
addressable, but just in ~4G chunks.

> The point is that each process is limited to 4GB, but the kernel can map
> that 4GB differently for each process. This happens anyway since you don't
> want different processes seeing each others' memory.

Right - got that.

> Note that the kernel uses the top GB of each processes virtual memory, ie
> 0 to < 3GB is usableby the process >3GB to < 4GB is used by the kernel.

Right - and this is tuneable - you can have 4G - a power of 2 reserved
for the kernel - 1G being the default?

S.
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