On Fri, Jul 08, 2016 at 10:34:42AM +0100, Mel Gorman wrote: > kswapd checks all eligible zones to see if they need balancing even if it > was woken for a lower zone. This made sense when we reclaimed on a > per-zone basis because we wanted to shrink zones fairly so avoid > age-inversion problems. Ideally this is completely unnecessary when > reclaiming on a per-node basis. In theory, there may still be anomalies > when all requests are for lower zones and very old pages are preserved in > higher zones but this should be the exceptional case. > > Signed-off-by: Mel Gorman <mgor...@techsingularity.net> > Acked-by: Vlastimil Babka <vba...@suse.cz>
Acked-by: Johannes Weiner <han...@cmpxchg.org> I wasn't quite sure at first what the rationale is for this patch, since it probably won't make much difference in pratice. But I do agree that the code is cleaner to have kswapd check exactly what it was asked to check, rather than some do-the-"right"-thing magic. A hypothetical onslaught of low-zone allocations will wreak havoc to the page age in higher zones anyway, right? So I don't think that case matters all that much.
