Author: Robert Hyatt
Date: 12:27:09 11/12/03
Go up one level in this thread
On November 12, 2003 at 15:15:12, Brian Richardson wrote: >On November 12, 2003 at 13:34:09, Robert Hyatt wrote: > >>On November 12, 2003 at 13:18:48, Matthew Hull wrote: >> >>>On November 12, 2003 at 12:18:22, Anthony Cozzie wrote: >>> >>>>On November 12, 2003 at 11:55:20, Gian-Carlo Pascutto wrote: >>>> >>>>>On November 11, 2003 at 23:42:45, Eugene Nalimov wrote: >>>>> >>>>>>My point is: it's possible that due to the fact that quad Opteron is NUMA -- >not SMP -- system, for SMP-only program performance on quad Opteron can be >>>>>>worse than on *real* quad SMP system, even when for one CPU Opteron >>>>>>performance is much better. Itanium was used only as an example of such >>>>>>system, I never recommended rewriting any program for it. >>>>> >>>>>I don't understand how. The NUMA part is RAM. Even worst case on the Opteron >>>>>RAM is faster than Xeon SMP. So how could it ever be worse? >>>>> >>>>>-- >>>>>GCP >>>> >>>>Aaron's argument is: if a 1x opteron is faster than a 1x Xeon, a 4x opteron will >>>>be faster than a 4x Xeon. >>>> >>>>Nalimov is saying that Fritz may scale worse on the opteron due to NUMA issues. >>>>In other words, this is comparing latency with 1x opteron and NUMA opteron >>>>relative to 1x Xeon vs SMP Xeon. >>>> >>>>Off hand this seems logical to me . . . >>> >>>Perhaps Eugene can tell us if SMP crafty was slower on 2x opteron than Bob's 2x >>>Xeon, before the NUMA mods were made? >>> >>>MH >> >>Yes. It was _really_ bad on the opteron. But then again it was also not >>real good on my xeon. > >Might you have meant bad on Athlon, not Opteron? No. It was bad on athlon. _really_ bad on opteron. :) > >Even though the NPS scaled _perfectly_ on my older >>quad xeons. The PIV went to a longer cache line, which caused some coherency >>overhead that hurt. This has been addressed in the current code. But the >>problem was worse on the opteron due to the NUMA delays, compared to the >>PIV xeons which simply have a longer cache line to aggravate the problem. >> >> >> >> >>> >>>> >>>>anthony
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