On Tue, 10 Nov 2015, Ben Hutchings wrote:

quoted

I know this patch is in -mm and hasn't been merged by Linus yet, but I'm 
wondering why the multiple /proc/sys/vm/drop_caches is helping?  Would it 
simply suffice to put a sleep in there instead or is drop_caches actually 
doing something useful a second time around?

Initially I just retried setting nr_hugepages up to 10 times, which
wasn't sufficient.  Then I added the drop_caches, and after that
setting nr_hugepages tended to worked first time so I reduced the retry
count.  It might not be necessary to retry at all.

Ok, thanks.  I was just trying to make sure that the additional 
drop_caches wasn't actually required for the test, in which case we would 
have to fix drop_caches :)