On Wed, Mar 15, 2017 at 05:28:43PM +0100, Michal Hocko wrote: ... ... > After all the amount of the work to be done is the same we just risk > more lock contentions, unexpected CPU usage etc.
I start to realize this is a good question. I guess max_active=4 produced almost the best result(max_active=8 is only slightly better) is due to the test box is a 4 node machine and therefore, there are 4 zone->lock to contend(let's ignore those tiny zones only available in node 0). I'm going to test on a EP to see if max_active=2 will suffice to produce a good enough result. If so, the proper default number should be the number of nodes. Thanks.
