On 25/05/07, Garrett D'Amore <garrett at damore.org> wrote: > > The third problem is that kstat collection under Nemo is expensive for > drivers that need to do non-trivial effort to collect statistics. By > that, I mean that if you have to reclaim buffers, or do some other > expensive operation, to get accurate statistics, then you want to do it > _once_ for a given kstat snapshot. With Nemo, you don't get to know > about the start/end of snapshots, so instead of having one expensive > operation amortized across all the stats, you have one expensive > operation _per_ statistic. Not a pretty way to do this. >
But why change Nemo in this respect? If the stats. gathering operation is expensive for the driver then it should be the *driver* that decides how frequently it's going to do the operation. It's pretty straightforward to stash an lbolt value in the getstat() entry point to limit how frequently the driver pulls counters from the h/w. The interface should not try to second guess the nature of the hardware and, in this case, I see no need to complicate the interface. Paul -- Paul Durrant http://www.linkedin.com/in/pdurrant
