On Fri, Apr 11, 2014 at 01:00:29PM -0400, [email protected] wrote: > From: Rik van Riel <[email protected]> > > Setting the numa_preferred_node for a task in task_numa_migrate > does nothing on a 2-node system. Either we migrate to the node > that already was our preferred node, or we stay where we were. > > On a 4-node system, it can slightly decrease overhead, by not > calling the NUMA code as much. Since every node tends to be > directly connected to every other node, running on the wrong > node for a while does not do much damage. >
Guess what size of machine I do the vast bulk of testing of automatic NUMA balancing on! > However, on an 8 node system, there are far more bad nodes > than there are good ones, and pretending that a second choice > is actually the preferred node can greatly delay, or even > prevent, a workload from converging. > > The only time we can safely pretend that a second choice > node is the preferred node is when the task is part of a > workload that spans multiple NUMA nodes. > > Signed-off-by: Rik van Riel <[email protected]> > Tested-by: Vinod Chegu <[email protected]> Acked-by: Mel Gorman <[email protected]> -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
