On Tue, 18 Oct 2011, Andi Kleen wrote: > > Would it make sense to have the ZVC delta be tuneable (via /proc/sys/vm?), keeping the > > same default behavior as what we currently have? > > Tunable is bad. We don't really want a "hundreds of lines magic shell script to > make large systems perform". Please find a way to auto tune. > Agreed, and I think even if we had a tunable that it would result in potentially erradic VM performance because some areas depend on "fairly accurate" ZVCs and it wouldn't be clear that you're trading other unknown VM issues that will affect your workload because you've increased the deltas. Let's try to avoid having to ask "what is your ZVC delta tunable set at?" when someone reports a bug about reclaim stopping preemptively. That said, perhaps we need higher deltas by default and then hints in key areas in the form of sync_stats_if_delta_above(x) calls that would do zone_page_state_add() only when that kind of precision is actually needed. For public interfaces, that would be very easy to audit to see what the level of precision is when parsing the data. -- 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>