On Tue, Feb 11, 2020 at 02:47:19PM -0800, Alexander Duyck wrote: > From: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> > > In order to keep ourselves from reporting pages that are just going to be > reused again in the case of heavy churn we can put a limit on how many > total pages we will process per pass. Doing this will allow the worker > thread to go into idle much more quickly so that we avoid competing with > other threads that might be allocating or freeing pages. > > The logic added here will limit the worker thread to no more than one > sixteenth of the total free pages in a given area per list. Once that limit > is reached it will update the state so that at the end of the pass we will > reschedule the worker to try again in 2 seconds when the memory churn has > hopefully settled down. > > Again this optimization doesn't show much of a benefit in the standard case > as the memory churn is minmal. However with page allocator shuffling > enabled the gain is quite noticeable. Below are the results with a THP > enabled version of the will-it-scale page_fault1 test showing the > improvement in iterations for 16 processes or threads. > > Without: > tasks processes processes_idle threads threads_idle > 16 8283274.75 0.17 5594261.00 38.15 > > With: > tasks processes processes_idle threads threads_idle > 16 8767010.50 0.21 5791312.75 36.98 > > Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> Seems fair. The test case you used would have been pounding on the zone lock at fairly high frequency so it represents a worst-case scenario but not necessarily an unrealistic one Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
