ITEM: L5522L

questions on smp verses mpp

Question:

questions on smp verses mpp

Response:

DESC: Customer has a vendor that is trying to sell them a product.  
  He is wanting to know the difference between the SMP architecture
and the MPP architecture.  

 SMP - Symetric Multiple Processor (I think).
 MPP - Multiple Parallel Processor (I think).

  


Response:


SMP is normally defined as a symmetrical multi-processor architecture
where multiple CPUs are under the control of one copy of an operating
system, and memory and I/O devices can be addressed by
any of the CPUs in such a configuration. The memory and
I/O devices are shared amongst all the CPUs. SMP processors give
up a percentage of overall performance to the overhead associated with
maintaining the necessary locks on shared resources such
as physical memory as the number of CPUs in the
configuration "scales" or grows. For example a 2-way SMP may deliver
performance that is 1.6 times a uni-processor, a 3-way SMP may deliver
2.5 times the performance of a uniprocessor etc... The management of
these locks is normally performed by the operating system and consumes
a percentage of the available processing cycles that increases as the
number processes in the configuration increases.  Hence the
observation that the SMP architecture does scale, but only to a point.

MPP is usually defined as a massively parallel processor where
multiple CPUs each run their own unique copy of an operating system
and each also has its own uniquely addressable memory. I/O devices can
sometimes be "shared" amongst the "nodes" or processors of
an MPP configuration, but how these I/O devices are shared is
sometimes implemented in software device drivers, or in
additional cabling, or redundant physical connections to the same I/O
device from more than one individual processor. As an MPP
configuration does not have as much overhead to deal with in terms of
the locks on shared resources like physical memory which much be
managed by the operating system in an SMP, the performance for a lot
of workloads will scale linearly as the number of processors in the
configuration is increased. In general, the performance of MPP
configurations will scale much more linearly as compared to SMP
implementations, especially where the workloads being run do not
require interaction with a lock manager of some sort when accessing
I/O devices.



Support Line: questions on smp verses mpp ITEM: L5522L

Dated: August 1994 Category: N/A

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