Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE

[Anshuman Khandual]

On 05/22/2017 11:42 AM, Mike Rapoport wrote:
> Currently applications can explicitly enable or disable THP for a memory
> region using MADV_HUGEPAGE or MADV_NOHUGEPAGE. However, once either of
> these advises is used, the region will always have
> VM_HUGEPAGE/VM_NOHUGEPAGE flag set in vma->vm_flags.
> The MADV_CLR_HUGEPAGE resets both these flags and allows managing THP in
> the region according to system-wide settings.

Invoking madvise() for the first time with either MADV_HUGEPAGE or
MADV_NOHUGEPAGE on the buffer will unsubscribe it from the system
wide behavior for good. I am not saying we should not have a way
to put it back into system wide mode but are there no other functions
through madvise() or any other interface which may have the same
situation.