Re: [SSI-users] Can OpenSSI Be Used for General-Purpose Computing?

[John H. <jo...@Ca...>]

Will Keaney wrote:
> Hello.
> I came across your project while doing some research on Linux 
> clustering.  One question that I don't find clearly answered in the 
> available documentation is, can unmodified applications be run on an 
> OpenSSI cluster?  The other clustering solutions I have found all 
> require specially modified code to use their libraries (Beowulf, PVM, 
> et al), and I am really looking for something that is more versatile.
An OpenSSI cluster tries to look as much like one big multi-processor 
machine as possible.

The limitations are all related to the (much) higher latency/lower 
throughput for inter-node memory access.

So:

   1. Cross-node shared memory is slower than normal shared memory.
   2. Other forms of cross-node IPC are slower (Unix domain sockets,
      SysV semaphores, SysV message queues).
   3. Multi-threaded applications run with all threads on one node.
   4. Accesses to filesystems mounted on other nodes are slower.

If your application can be written as many mostly independent processes 
then OpenSSI should be very easy to use and give acceptable 
performance.  (A good example: Linux kernel compiles with "-j" set to 
number of nodes times number of cores).