Author: Robert Hyatt
Date: 22:12:37 02/01/05
Go up one level in this thread
On February 02, 2005 at 00:03:26, Matthew Hull wrote: > >>>> >>>>Quote on: >>>>------------------------------------------ >>>> >>>>It's 4 nodes. >>>> >>>>1 node = 8 processor Xeon. >>>>------------------------------------------ >>>>quote off >>>> >>>>"one node = 8 processor xeon". That is _clearly_ SMP. And _that_ is the box I >>>>was talking about. I've run on more than one of them. For chess they are bad, >>>>running 2 copies of crafty produces 2x NPS of one copy. Running 4 copies >>>>produces nearly 4x the NPS of one copy. Running 8 copes produces barely 6x the >>>>1 copy speed. >>> >>> >>>Would this be considered a NUMA relationship, between the two 4-way nodes. Does >>>your NUMA crafty handle this better than your older SMP-only crafty? >>> >> >> >>wasn't numa. Used the Intel "Fusion" chipset to tie two 4-way processor groups >>together to provide a total of 8, but there was a bottleneck. It was one of >>those "let's see what it will do" sort of things. Big L2 cache processors could >>provide good performance if memory requirements were limited. >>I'll take a NUMA opteron system any day. > > >I see now. > >What then was the issue with the dual Athlons? IIRC, the memory was not >interleaved, so SMP crafty did not do as well on those as on dual Xeon. Did >your NUMA changes help with dual Athlons? > >Thanks, > They used MOESI cache coherency. Intel prior to the PIV xeon used MESI. MOESI uses a cache-to-cache communication link that will let one cache share a line of modified data with the other without going thru memory as a MESI cache does. Problem is that it is possible to swamp this channel, which is what I was doing. By reorganizing shared but not modified data and moving it away from shared/modified data (like spin locks for example) that cache update traffic was reduced significantly... > > >> >> >>
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.