Utilising a CMT system

I got asked about how to utilise a CMT system, it's probably not an uncommon question, so I'll post my (somewhat brief) answer here:

The CMT processor appears as a system with many CPUs. These virtual CPUs can be provisioned in the same way as you would with any multiprocessor system:

  • The OS will naturally handle positioning multiple active threads so as to get the optimal performance.
  • If you wish to manually tune this then you can use Solaris tools like processor binding (pbind, or processor_bind) to statically allocate a particular thread or process to a particular core. You can use processor sets (psrset) to restrict a set of processes to a particular set of processors (or to exclude particular processes from using these processors).
  • The machine can be divided into multiple virtual machines either through Solaris Zones, where all zones run the same version of the Solaris operating system. Or through logical domains where multiple different operating systems can be installed onto the same machine.
    • The optimal configuration will depend on the problem to be solved.

      I've actually heard someone argue that multicore processors require a redesign of applications. Um, no. Applications will work just fine. However, multicore processors do give you opportunities to throw more threads at a problem - which can be very useful.

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About

Darryl Gove is a senior engineer in the Solaris Studio team, working on optimising applications and benchmarks for current and future processors. He is also the author of the books:
Multicore Application Programming
Solaris Application Programming
The Developer's Edge

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