On Wed, 29 Sep 2010, Mel Gorman wrote: > > Updating the threshold also is expensive. > > Even if it's moved to a read-mostly part of the zone such as after > lowmem_reserve? The threshold is stored in the hot part of the per cpu page structure. > > I thought more along the lines > > of reducing the threshold for good if the VM runs into reclaim trouble > > because of too high fuzziness in the counters. > > > > That would be unfortunate as it would only take trouble to happen once > for performance to be impaired for the remaining uptime of the machine. Reclaim also impairs performance and inaccurate counters may cause unnecessary reclaim. Ultimately this is a tradeoff. The current thresholds were calculated so that there will be zero impact even for very large configurations where all processors continual page fault. I think we have some leeway to go lower there. The tuning situation was a bit extreme. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>