slim@cis.ohio-state.edu (Scott Whitman) (12/14/89)
Howdy folks,
I am in the process of optimizing my program for running on
the BBN Butterfly GP1000. I was wondering if anyone has any
suggestions for looking at how to tune the program for good speedup.
I had been working on a small Butterfly (9 nodes) and got reasonable
speedup. When I finally moved to a larger machine, I noticed that
at 24 nodes, the performance was worse than with 8. Needless to say,
this is not a desirable affect.
My first thought was memory contention, but I have scattered
most of the data and gotten rid of any unnecessary data structures.
My feeling is that this still may be the problem, however, I am at a
loss at the moment to figure out where the problem lies. I do have
the TotalView debugger and gist, but these haven't helped much. The
program looks like it is evenly load balanced, even on 24 nodes, but
the performance obviously indicates that there is a bottleneck
somewhere.
If anyone has any suggestions, I'd appreciate it. Please mail
me at: slim@cosimo.osgp.osc.edu.
Thanks,
-Scott Whitman
--
Scott Whitman, Department of Computer and Information Science
slim@cis.ohio-state.edu or ...!{pyramid,killer}!osu-cis!slim
The Ohio State University; 2036 Neil Ave. Columbus OH USA 43210-1277cleary@uunet.UU.NET (John Cleary) (12/14/89)
In article <7385@hubcap.clemson.edu>, slim@cis.ohio-state.edu (Scott Whitman) writes: > I am in the process of optimizing my program for running on > the BBN Butterfly GP1000. I was wondering if anyone has any > suggestions for looking at how to tune the program for good speedup. > I had been working on a small Butterfly (9 nodes) and got reasonable > speedup. When I finally moved to a larger machine, I noticed that > at 24 nodes, the performance was worse than with 8. Needless to say, > this is not a desirable affect. There is a known problem on the Buuterfly implementation of Mach where it has a tendency to keep te page tables for a number of nodes on one node. There are also a number of other places whree there are centralized data structures. I dont understand all the details of this but others have reported effects just like yours. As to a fix I cant help much. Maybe wait for the next release oft he operating system :-) John G. Cleary Department of Computer Science University of Calgary 2500 University Drive N.W. Calgary Alberta T2N 1N4 Canada cleary@cpsc.UCalgary.ca Phone: (403)282-5711 or (403)220-6087