On Wed 31-05-17 15:39:22, Mike Rapoprt wrote:

On May 31, 2017 3:08:22 PM GMT+03:00, Michal Hocko [off-list ref] wrote:

[...]

quoted

From what Mike said a global disable THP for the whole process
while the post-copy is in progress is a better solution anyway.

For the CRIU usecase, disabling THP for a while and re-enabling
it back will do the trick, provided VMAs flags are not affected,
like in the patch you've sent.  Moreover, we may even get away with
ioctl(UFFDIO_COPY) if it's overhead shows to be negligible.  Still,
I believe that MADV_RESET_HUGEPAGE (or some better named) command has
the value on its own.

I would prefer if we could go the prctl if possible and add a new
MADV_RESET_HUGEPAGE if there is really a usecase for it.
-- 
Michal Hocko
SUSE Labs