On Thu, Oct 04, 2012 at 01:50:42AM +0200, Andrea Arcangeli wrote: > Hello everyone, > > This is a new AutoNUMA27 release for Linux v3.6. > So after getting through the full review of it, there wasn't anything I could not stand. I think it's *very* heavy on some of the paths like the idle balancer which I was not keen on and the fault paths are also quite heavy. I think the weight on some of these paths can be reduced but not to 0 if the objectives to autonuma are to be met. I'm not fully convinced that the task exchange is actually necessary or beneficial because it somewhat assumes that there is a symmetry between CPU and memory balancing that may not be true. The fact that it only considers tasks that are currently running feels a bit random but examining all tasks that recently ran on the node would be far too expensive to there is no good answer. You are caught between a rock and a hard place and either direction you go is wrong for different reasons. You need something more frequent than scans (because it'll converge too slowly) but doing it from the balancer misses some tasks and may run too frequently and it's unclear how it effects the current load balancer decisions. I don't have a good alternative solution for this but ideally it would be better integrated with the existing scheduler when there is more data on what those scheduling decisions should be. That will only come from a wide range of testing and the inevitable bug reports. That said, this is concentrating on the problems without considering the situations where it would work very well. I think it'll come down to HPC and anything jitter-sensitive will hate this while workloads like JVM, virtualisation or anything that uses a lot of memory without caring about placement will love it. It's not perfect but it's better than incurring the cost of remote access unconditionally. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>