On Fri, Jun 21, 2019 at 12:43:25PM +0100, Alan Jenkins wrote: > When setting the low and high watermarks we use min_wmark_pages(zone). > I guess this is to reduce the line length. But we forgot that this macro > includes zone->watermark_boost. We need to reset zone->watermark_boost > first. Otherwise the watermarks will be set inconsistently. > > E.g. this could cause inconsistent values if the watermarks have been > boosted, and then you change a sysctl which triggers > __setup_per_zone_wmarks(). > > I strongly suspect this explains why I have seen slightly high watermarks. > Suspicious-looking zoneinfo below - notice high-low != low-min. > > Node 0, zone Normal > pages free 74597 > min 9582 > low 34505 > high 36900 > > https://unix.stackexchange.com/questions/525674/my-low-and-high-watermarks-seem-higher-than-predicted-by-documentation-sysctl-vm/525687 > > Signed-off-by: Alan Jenkins <alan.christopher.jenkins@xxxxxxxxx> > Fixes: 1c30844d2dfe ("mm: reclaim small amounts of memory when an external > fragmentation event occurs") > Cc: stable@xxxxxxxxxxxxxxx Either way Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> -- Mel Gorman SUSE Labs
