On Tue, Nov 17, 2020 at 03:24:56PM +0100, Vincent Guittot wrote: > On Tue, 17 Nov 2020 at 14:42, Mel Gorman <mgor...@techsingularity.net> wrote: > > > > Currently, an imbalance is only allowed when a destination node > > is almost completely idle. This solved one basic class of problems > > and was the cautious approach. > > > > This patch revisits the possibility that NUMA nodes can be imbalanced > > until 25% of the CPUs are occupied. The reasoning behind 25% is somewhat > > superficial -- it's half the cores when HT is enabled. At higher > > utilisations, balancing should continue as normal and keep things even > > until scheduler domains are fully busy or over utilised. > > This reminds me previous discussions on the same topic: how much > imbalance is allowed that will not screw up the bandwidth of the node > I'm worried that there is no topology insight in the decision like > hyperthreading, or number of cpus in the LLC >
We still don't have a good answer for that. It could be a tunable I guess but it would be horrible to tune properly. -- Mel Gorman SUSE Labs
