Author: Brian Richardson
Date: 12:15:12 11/12/03
Go up one level in this thread
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? 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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