On 2/26/07, Rajat Jain <rajat.noida.india@xxxxxxxxx> wrote:
On 2/26/07, Mansha Linux <mansha.linux@xxxxxxxxx> wrote:
>
>
> On 2/25/07, Jarod Wang <mailtojarod@xxxxxxxxx> wrote:
> > 2007/2/25, Mansha Linux <mansha.linux@xxxxxxxxx >:
> > > hi all,
> > >
> > > For a 32-bit machine, there is total 4GB of memory(Physiacl addresses).
> So
> > > in that 1 GB for Kernel and 3GB for User Space.
> > The kernel (on the x86 architecture, in the default configuration)
> > splits the 4-GB *virtual address space* between user-space and the
> > kernel; the same set of mappings is used in both contexts. A typical
> > split dedicates 3 GB to user space, and 1 GB for kernel space.
> >
> > > So, kernel won't access that 3GB of memory, right?
> > > All the kernel code is exist in 1 GB of memory.... CMIIW
> > All the kernel code is linked using 0xC0000000(3GB, also virtual
> > address) as the base address.
> >
> > > So, my doubt is the
> > > DMA(0-16MB),NORMAL(16-896MB),HIGH(896MB-) memory
> divided
> > > within this 4GB of memory ,right?
> > Within 4GB physical addresses space.
> >
> > > if we allocate the pages using alloc_pages, from which region the pages
> are
> > > allocated for the kernel modules. is it from Physical RAM memory or from
> 1GB
> > > of kernel space ??
> > From physical memory.
> >
> >
> >
> > --
> > Best regards,
> >
> > Jarod Wang
> > ----
> > Wuhan University of Technology, Wuhan, P. R. China
> >
>
> Jarod thanks for ur reply
>
> >The kernel (on the x86 architecture, in the default configuration)
> >splits the 4-GB *virtual address space* between user-space and the
> >kernel; the same set of mappings is used in both contexts. A typical
> >split dedicates 3 GB to user space, and 1 GB for kernel space.
>
> Q->it means for a 32-bit machine all 4GB space is Virtual Addresses not
> Physical addresses ?
>
You CAN connect physical memory upto the maximum size your
architecture allows (For 32 bit CPU, this is generally 4GB memory - It
can be more with mechanisms like PAE). The virtual address space will
always be 4 GB though.
So, where ever we specify the Physical addresses or Physical memory means the System RAM memory which is mapped within the 4GB ...right?
--
regards,
Mansha
