From owner-freebsd-hackers@freebsd.org  Mon Oct 12 20:11:21 2015
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Date: Mon, 12 Oct 2015 16:11:19 -0400
Message-ID: <CAJOqHmitGr2oEnNheoG2MQYVcwsPNFyPHqhsTA+sAC40Yqw0Rg@mail.gmail.com>
Subject: kernel pages superpage promotion/demotion
From: suresh gumpula <gsuryacse7k@gmail.com>
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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 ?

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 ?

Could some one with VM expertise please comment on this ?

Thanks
Suresh