On Tue, Jul 12, 2016 at 02:32:45PM +0800, Hillf Danton wrote: > > > To avoid excessive reclaim, we give up rebalancing for high order > > > allocations right after reclaiming enough pages. > > > > hm. What are the observed runtime effects of this change? Any testing > > results? > > > This work was based on Mel's work, Sir, > "[PATCH 00/27] Move LRU page reclaim from zones to nodes v7". >
I believe Andrew understands that but the question is what is the observed runtime effect of the patch? > In "[PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes", > fragmentation detection is introduced to avoid excessive reclaim. We bail > out of balancing for high-order allocations if the pages reclaimed at the > __current__ reclaim priority are two times more than required. > > In this work we give up reclaiming for high-order allocations if the > __total__ number of pages reclaimed, from the first priority to the > current priority, is more than needed, and in net result we reclaim less > pages. > While it's clear what it does, it is not clear if it is an improvement. I had read the patch, considered merging it and decided against it. This decision was based on the fact the series did not appear to be over-reclaiming for high-order pages when compared with zone-lru. Did you test this patch with a workload that requires a lot of high-order pages and see if kswapd was over-reclaiming and that this patch addressed the issue? -- Mel Gorman SUSE Labs
