On Tue, Feb 11, 2020 at 02:47:08PM -0800, Alexander Duyck wrote: > From: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> > > Rather than walking over the same pages again and again to get to the pages > that have yet to be reported we can save ourselves a significant amount of > time by simply rotating the list so that when we have a full list of > reported pages the head of the list is pointing to the next non-reported > page. Doing this should save us some significant time when processing each > free list. > > This doesn't gain us much in the standard case as all of the non-reported > pages should be near the top of the list already. However in the case of > page shuffling this results in a noticeable improvement. Below are the > will-it-scale page_fault1 w/ THP numbers for 16 tasks with and without > this patch. > > Without: > tasks processes processes_idle threads threads_idle > 16 8093776.25 0.17 5393242.00 38.20 > > With: > tasks processes processes_idle threads threads_idle > 16 8283274.75 0.17 5594261.00 38.15 > > Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> Thanks for pulling this patch out and noting its impact. I think the rotation is ok and if it turns out I missed something, it'll be relatively easy to back out just the optimisation and leave the rest of the feature intact. Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
