Josiah mentioned requesting a free trial of the ZIng JVM.  Did you ever get 
access to that, and were able to try your code running on that?

Again, I have no direct experience with their product to guarantee you better 
results -- just that I've heard good things about their ability to handle 
concurrent workloads with different GC than most JVMs.

Andy

On Jan 30, 2013, at 6:20 PM, Lee Spector wrote:

> 
> FYI we had a bit of a discussion about this at a meetup in Amherst MA 
> yesterday, and while I'm not sufficiently on top of the JVM or system issues 
> to have briefed everyone on all of the details there has been a little of 
> followup since the discussion, including results of some different 
> experiments by Chas Emerick, at: 
> http://www.meetup.com/Functional-Programming-Connoisseurs/messages/boards/thread/30946382
> 
> -Lee
> 
> On Jan 30, 2013, at 8:39 PM, Marshall Bockrath-Vandegrift wrote:
>> 
>> Apologies for my very-slow reply here.  I keep thinking that I’ll have
>> more time to look into this issue, and keep having other things
>> requiring my attention.  And on top of that, I’ve temporarily lost the
>> many-way AMD system I was using as a test-bed.
>> 
>> I very much want to see if I can get my hands on an Intel system to
>> compare to.  My AMD system is in theory 32-way – two physical CPUs, each
>> with 16 cores.  However, Linux reports (via /proc/cpuinfo) the cores in
>> groups of 8 (“cpu cores : 8” etc).  And something very strange happens
>> when extending parallelism beyond 8-way...  I ran several experiments
>> using a version of your whole-application benchmark I modified to
>> control the level of parallelism.  At parallelism 9+, the real time it
>> takes to complete the benchmark hardly budges, but the user/CPU time
>> increases linearly with the level of parallelism!  As far as I can tell,
>> multi-processor AMD *is* a NUMA architecture, which might potentially
>> explain things.  But enabling the JVM NUMA options doesn’t seem to
>> affect the benchmark.
>> 
>> I think next steps are two-fold: (1) examine parallelism vs real & CPU
>> time on an Intel system, and (2) attempt to reproduce the observed
>> behavior in pure Java.  I’m keeping my fingers crossed that I’ll have
>> some time to look at this more soon, but I’m honestly not very hopeful.
>> 
>> In the mean time, I hope you’ve managed to exploit multi-process
>> parallelism to run more efficiently?
>> 
>> -Marshall

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