kernel pages superpage promotion/demotion

[Alan Cox]

On Mon, Oct 12, 2015 at 3:11 PM, suresh gumpula <gsuryacse7k at gmail.com>
wrote:

> Hi,
>       I understand that user space VM map pages dynamically
> promoted/demoted to super page
>   if the kernel thinks that it gains the performance.
>         The question is  , does this apply to kernel map pages too ?
>
>

Yes, it applies to memory allocated for UMA zones, malloc(9), and
contigmalloc(9).



> And is it possible to write protect kernel address space VA with
>  pmap_protect(9).   Since the protection is per 4k page,  I see this
> routine tries to demote to 4k page.
> Or this is only for user space maps to support  mprotect(2) and gdb
> watchpoints.
> Do we have any other API to write protect kernel addresses which come from
> UMA zone allocations ?
>
>

No.

Can you please try to describe what are you trying to do at a higher level?