Re: Issue using UPC on Opteron Cluster

From: Dan Bonachea (bonachea_at_cs_dot_berkeley_dot_edu)
Date: Fri Nov 03 2006 - 14:31:34 PST

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    At 06:13 AM 11/3/2006, Alexandre Chauvin wrote:
    >Thank you Dan for this quick reply. I will give it a try even if I saw that I 
    >have to download the Beta version 2.3.16 of UPC to be compatible with PPW. I 
    >was trying with version 2.2.2 so far.
    >I will keep you updated.
    Great - let us know how it goes..
    >Another quick question is that I am facing some difficulties to allocate more 
    >than 1.3GB of RAM per thread with the vapi conduct. Can U see any explanation 
    >for that?
    Did you pass the -shared-heap flag to upcrun to request the amount of shared 
    memory size you need?
    If it's still not behaving the way you believe it should, please submit a bug 
    report with complete information on your setup and how to reproduce the 
    problem at
    >On 11/3/06, Dan Bonachea 
    ><<mailto:[email protected]>bonachea_at_cs_dot_berkeley_dot_edu> wrote:
    >Hi Alexandre -
    >    This is a common experience for UPC programs that are written in a
    >shared-memory style without regard for locality, when run for the first time
    >in a distributed-memory environment (where locality is extremely important 
    >good performance, because communication is orders of magnitude more expensive
    >across nodes than within a shared-memory node).
    >    Chances are you have some communication-related performance bugs in your
    >application - possibly due to the layout of your main data structures, but
    >possibly also just communication "leaks" from accidental or trivial sharing 
    >data where things need to be tuned.
    >    Luckily, we now have a very nice performance tool designed specifically 
    > to
    >help UPC programmers find and fix such problems, called the Parallel
    >Performance Wizard:
    >                      <>
    >    I strongly encourage you to download it and give it a try. The PPW team 
    > is
    >very receptive to feedback about the performance tool, and probably would 
    >help you to track down your performance issues if they aren't immediately
    >obvious in the tool output.
    >Hope this helps..
    >At 01:30 AM 11/3/2006, Alexandre Chauvin wrote:
    > >Hello All --
    > >
    > >I am facing some issues when trying to run a UPC code on an Opteron Cluster
    > >environement. I am quite newbie with UPC so the answer could be very 
    > trivial.
    > >Could you please have a look?
    > >
    > >I would like to use my whole cluster to do a sort. But, if the code goes 
    > very
    > >fast when using 8GB memory with pthreads within a single node, it goes very
    > >slow as soon as I try to use multiple nodes.
    > >
    > >I tried both vapi and mpi conducts -- infiniband interconnect -- but
    > >performance was very bad. It went from 1min on 1 node to more than 20mins
    > >when using 2nodes!
    > >
    > >
    > >Is it something particular I should do to use multiple nodes mode
    > >efficiently?
    > >

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