kernel pages superpage promotion/demotion

suresh gumpula gsuryacse7k at gmail.com
Mon Oct 12 20:11:21 UTC 2015


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


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