On Thu, 14 Oct 2010, KOSAKI Motohiro wrote: > Initial variable ZVC commit (df9ecaba3f1) says > > > [PATCH] ZVC: Scale thresholds depending on the size of the system > > > > The ZVC counter update threshold is currently set to a fixed value of 32. > > This patch sets up the threshold depending on the number of processors and > > the sizes of the zones in the system. > > > > With the current threshold of 32, I was able to observe slight contention > > when more than 130-140 processors concurrently updated the counters. The > > contention vanished when I either increased the threshold to 64 or used > > Andrew's idea of overstepping the interval (see ZVC overstep patch). > > > > However, we saw contention again at 220-230 processors. So we need higher > > values for larger systems. > > So, I'm worry about your patch reintroduce old cache contention issue that Christoph > observed when run 128-256cpus system. May I ask how do you think this issue? The load that I ran with was a test that concurrently faulted pages on a large number of processors. This is a bit artificial and is only of performance concern during startup of a large HPC job. The frequency of counter updates during regular processing should pose a much lighter load on the system. The automatic adaption of the thresholds should 1. Preserve the initial startup performance (since the threshold will be unmodified on a system just starting). 2. Reduce the overhead of establish a more accurate zone state (because reclaim can then cause the thresholds to be adapted). -- 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>