Agner`s CPU blog

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Test results for AMD Bulldozer processor
Author:  Date: 2012-04-03 05:24
Agner wrote:
  • Some operating systems are not aware that the chip shares certain resources between the two cores that make up a compute unit. The consequence is that the operating system may put two threads into one compute unit while another unit is idle, or it may put two threads with different priority into the same compute unit so that a low priority thread can steal resources from a high priority thread. I don't understand why there is no CPUID function for telling which resources are shared between CPU cores. The current solution where the operating system must know the details of every CPU on the market is not practical, and it does not work with virtual CPUs etc.
     
  • The hardware locality project[1] attempts to deal with this to an extent, but so far it is only really used by a few, although it has been rolled into OpenMPI. I would agree that it isn't really ideal though. I don't expect the application programmers to start thinking about this stuff any time soon.

    [1]
    www.open-mpi.org/projects/hwloc/

     
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