On 12/19/2011 12:45 PM, KOSAKI Motohiro wrote: > (12/19/11 3:31 PM), Dave Hansen wrote: >> Let's say you profiled a application and the data shows you're missing >> the TLB a bunch, but you're also using THP. This might give you a shot >> at figuring out which parts of your application are *TRULY* THP-backed >> instead of just the areas you *think* are backed. >> >> I'm not sure there's another way to figure it out at the moment. > > A snapshot status of THP doesn't help your purpose. I think you need > perf or similar profiling subsystem enhancement. > > Because of, if you've seen KPF_THP at once, It has no guarantee to keep > hugepages until applications run. Opposite, If you only need rough > statistics, the best way is to add some new stat to > /sys/kernel/mm/transparent_hugepage. But, every single one of the pagemap flags is really just a snapshot KPF_DIRTY, KPF_LOCKED, etc... The entire interface is inherently a racy snapshot, and there's not a whole lot you can do about it. sys_mincore() has the exact same issues. But, that does not make them useless, nor mean they shouldn't be in the kernel. A tracepoint or something similar to watch for THP promotions or demotions would be a great addition to this interface. That way, you at least have a concept if the data you got has become stale. -- 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>