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    SubjectRe: RFC: NUMA modifications to cyclictest
    On Tue, 19 Jan 2010, Clark Williams wrote:
    > RT-ers,
    > Lately we've been struggling with some performance issues on high-core
    > count (>16 cores) NUMA machines with the RT kernel. During the course
    > of troubleshooting this issue, we tried using the 'numactl' program to
    > constrain our measurement testing tool (rteval) to a particular memory
    > node, rather than letting everything float. Doing so showed marked
    > improvement in both max latency and jitter. While this doesn't solve
    > our performance problems I thought it might make sense to have a --numa
    > mode for cylictest that compliments the --smp mode just added.
    > The big difference here is that when using --numa, each measurement
    > thread (one per cpu) has it's stack allocated from the memory node
    > associated with it's cpu. Also, the major data structures for each
    > thread (parameter block, statistics block and histogram) are allocated
    > from the appropriate node. This is done with calls into libnuma,
    > which means this will add a dependency on libnuma.

    That might cause some trouble for embedded folks. :(

    > The intent is to measure latency on a numa system in the same way a
    > well-written RT application would run on a NUMA machine, that is
    > minimizing the off-node memory references.



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