On Mon, May 22, 2017 at 12:56:45PM +0530, Anshuman Khandual wrote: > 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.
There are madvise() interfaces that set or clear some of the vma->vm_flags, e.g MADV_*FORK or MADV_*DUMP. The difference with MADV_*HUGEPAGE is that it is using two flags and with current madvise() interface either of them has to be set, but there is no interface to clear them both. -- Sincerely yours, Mike.
