Global Shared Memory and SCI/Dolphin

Ashley Pittman ashley at pittman.co.uk
Fri Jul 18 07:45:01 EDT 2003


On Thu, 2003-07-17 at 21:40, Richard Walsh wrote:
> Dan Kidger wrote:
> 
> >The Quadrics Interconnect also does hardware RDMA, and yes a significant
> >percentage of people do use Global Shared Memory programming models rather
> >than message passing.
> >
> >In fact I thought all four of SCALI/Quadrics/Myrinet/Infiniband could do
> >RDMA ??
> 
>  Does this support run all the way up the stack to the MPI-2 "one-sided"
>  communications stuff?  Anyone working on supporting the implicit DSM
>  language constructs of CAF and/or UPC with their RDMA capability?  Comments 
>  on any/all interconnects mentioned are welcome.

Yes it does, we support both Cray SHMEM and MPI-2 "one-sided" which are
essentially simple wrappers around the DMA engine.  Because it's truly
one-sided it's lower latency than Send/Recv.  I've included some pallas
figures from one of the machines here.

There are two UPC implementations which work over Quadrics hardware, one
of which is open source, check out http://upc.nersc.gov/

Ashley,


#---------------------------------------------------
# Benchmarking Unidir_Put 
# ( #processes = 2 ) 
#---------------------------------------------------
#
#    MODE: AGGREGATE 
#
       #bytes #repetitions      t[usec]   Mbytes/sec
            0         4096         0.07         0.00
            4         4096         1.67         2.28
            8         4096         1.68         4.55
           16         4096         1.72         8.86
           32         4096         2.19        13.95
           64         4096         2.55        23.89
          128         4096         2.77        44.06
          256         4096         3.19        76.60
          512         4096         4.14       118.06
         1024         4096         5.76       169.42
         2048         4096         8.95       218.30
         4096         4096        15.32       254.92
         8192         4096        28.00       279.04
        16384         2560        53.40       292.63
        32768         1280       104.10       300.19
        65536          640       207.56       301.12
       131072          320       412.33       303.15
       262144          160       821.94       304.16


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