On Wed, 3 Oct 2018, Michal Hocko wrote:

quoted

quoted

So how about this? (not tested yet but it should be pretty
straightforward)

Umm, prctl(PR_GET_THP_DISABLE)?

/me confused. I thought you want to query for the flag on a
_different_ process. 

Why would we want to check three locations (system wide setting, prctl 
setting, madvise setting) to determine if a heap can be backed by thp?

If the nh flag being exported to VmFlag is to be extended beyond what my 
patch did, I suggest (1) it does it for the system wide setting as well 
and/or (2) calling a helper function to determine if the vma could be 
backed by thp in the first place regardless of any setting to determine if 
nh/hg is important.

The last thing I suggest is done is adding a third place to check.