Re: Linux x86-32 addr space split

From: Mosa Atilles (mosatilla_at_gmail.com)
Date: 02/02/05 

Date: Wed, 02 Feb 2005 14:24:50 -0800

Josef Moellers wrote:
>
> The advantage is that the kernel will have the current process' address
> space as part of its own address space. In a large number of cases, this
> makes expensice copies between separate address spaces (user<->kernel)
> unnecessary.
> Note To stay portable, one should nonetheless use the appropriate
> functions/macros when copying between user and kernel space, even if
> they will then just to a copy.
>

Thanks Josef. That certainly does reduce a lot of overhead.
But then there is only so much kernel address space to accommodate the
various kernel data structs (pte, vma etc). That in turn constrains the
amount of shared memory that can be mapped into the process addr space.
  I guess it's a trade-off in favour of performance.
Thanks again, for imparting that clarity.

Quantcast