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Date: Mon, 12 Oct 2015 17:43:49 -0500
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Subject: Re: kernel pages superpage promotion/demotion
From: Alan Cox <alan.l.cox@gmail.com>
To: suresh gumpula <gsuryacse7k@gmail.com>
Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
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On Mon, Oct 12, 2015 at 3:11 PM, suresh gumpula <gsuryacse7k@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?