On 03/19/2012 02:20 PM, Peter Zijlstra wrote: > On Mon, 2012-03-19 at 13:42 +0200, Avi Kivity wrote: > > It's the standard space/time tradeoff. Once solution wants more > > storage, the other wants more faults. > > > > Note scanners can use A/D bits which are cheaper than faults. > > I'm not convinced.. the scanner will still consume time even if the > system is perfectly balanced -- it has to in order to determine this. > > So sure, A/D/other page table magic can make scanners faster than faults > however you only need faults when you're actually going to migrate a > task. Whereas you always need to scan, even in the stable state. > > So while the per-instance times might be in favour of scanning, I'm > thinking the accumulated time is in favour of faults. When you migrate a vnode, you don't need the faults at all. You know exactly which pages need to be migrated, you can just queue them immediately when you make that decision. The scanning therefore only needs to pick up the stragglers and can be set to a very low frequency. -- error compiling committee.c: too many arguments to function -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>