On Wed, Apr 22, 2009 at 1:27 PM, Dan Nelson <dnel...@allantgroup.com> wrote:
> In the last episode (Apr 22), Rod Heyd said: > > I've been running mysql on a T1000 (Ultrasparc T1) system for several > > years now, and while I've been happy with the performance overall, the > > poor floating point capability on these systems has been a > disappointment. > > Recently, I got my hands on a Sunfire T5420 system and I've been > comparing > > the floating point performance on this system with the T1000, and was > > expecting to see a significant improvement in floating point by virtue of > > the fact that the Ultrasparc T2 processor has 1 FPU per core as opposed > to > > 1 FPU per CPU. However, I'm only seeing a marginal improvement for > > floating point calculations, for example, a "select benchmark(100000000, > > 1.0 + 2.0)" takes roughly 50 seconds to run on both of these systems, > > however I was expecting a lot better performance from the T2 processor. > > If you are running just one command, then you are only using one of the 8 > FPUs on the T2. Try comparing 8 parallel "select benchmark(100000000, 1.0 > + > 2.0)" runs at once on each server. > Hi Dan, Yes, actually, I already know that parallel performance will be much improved, however, I was expecting more improvement on single threads as well, since the specs say that it takes 40 clock cycles just to access the FPU on the T1, but something like 6 clock cycles on the T2. So just from that perspective it seems like there should be a significant improvement for single threads, not just parallel performance. At least that's the way I read the docs from Sun on this. At any rate, my expectations here are clearly wrong, and I guess I'd just like a better understanding of why I'm getting it wrong. Thanks, Rod
