On Fri, 2010-08-13 at 15:57 -0400, Jim Rees wrote: > Patrick J. LoPresti wrote: > > On Fri, Aug 13, 2010 at 11:45 AM, john stultz <johnstul@xxxxxxxxxx> wrote: > > > On those TSC broken systems that use the hpet or acpi_pm, a > > getnstimeofday call can take 0.5-1.3us, so the penalty can be quite > > severe. > > So you are saying my proposal is a bad idea forever? (But then why > even bother having nanosecond resolution on ext4?) > > How about using getnstimeofday() only if the kernel clocksource is tsc? > Presumably anyone running into this problem would have modern high > performance hardware with working tsc. This might be difficult, as clocksources can change while the system is running. Further, any checks for specific clocksources would be very architecture specific. A fast-timekeeping flag could be used, but would be a fairly subjective metric (ie: would there be issues if the fast clock on a slower system is slower then a slow clock on a fast system, etc). That's partly why I suggested a mount option. thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
