On Fri, Feb 14, 2020 at 10:05:15AM +0800, Wei Yang wrote: > On Wed, Feb 12, 2020 at 07:43:33AM +0000, Mel Gorman wrote: > >Broadly speaking it was driven by cases whereby kswapd either a) fell > >asleep prematurely and there were many stalls in direct reclaim before > >kswapd recovered, b) stalls in direct reclaim immediately after kswapd went > >to sleep or c) kswapd reclaimed for lower zones and went to sleep while > >parallel tasks were direct reclaiming in higher zones or higher orders. > > Thanks for your explanation. I am trying to understand the connection between > those cases and the behavior of kswapd. > > In summary, all three cases are related to direct reclaim, while happens in > three different timing of kswapd: Reclaim performed by kswapd is the opposite of direct reclaim. Direct reclaim is reclaim initiated by a task which is trying to allocate memory. If a task cannot perform direct reclaim itself, it may ask kswapd to attempt to reclaim memory for it.
