Basic HighMeM Question

[mulyadi.santosa@gmail.com (Mulyadi Santosa)]

Hi :)

On Wed, Jun 29, 2011 at 13:30, piyush moghe <pmkernel@gmail.com> wrote:
> Thanks Mulyadi and Prabhu for your enlightening description.

You welcome :)

> What a plight!!! memory has become soo cheap nowadays that I don't have less
> than 1GB system and difficult to find someone in my knowledge having less
> than 1 GB memory.

In embedded world, it's still common scenario.... so it depends on
which side we see it :) That's the flexibility Linux kernel tries to
show...it does well on big memory machine...but it can also run in
small amount of memory... of course, with the right user space
applications :) (hint: Linux slitaz, puppy, tiny core...)


> Although does this means that pages in FCOM will never have page fault?

Everything mapped in kernel space ( I stress the word "mapped") is
designed to stay all the time in RAM in Linux kernel context. So based
on that AFAIK, we won't get page fault in kernel space. This is
strictly design choice IMHO.

>and
> if this is true is this the reason why we assign NULL to memory descriptor (
> mm_struct ) for kernel threads?

because kernel threads don't need to have specific address space owned
to them. They can simply "borrow" last scheduled process' address
space. After all, they just operate in kernel space, which is the same
for all processes, be it kernel threads or normal task.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com