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    SubjectRE: [PATCH v5 0/6] Add hardware prefetch control driver for A64FX and x86
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    >> The right way to solve this is to make the Linux kernel contain the necessary
    >> heuristics to identify which tasks and thus cores need this to improve efficiency
    >> and then apply it automatically.
    >>
    >> Putting it in userspace is making a human do a machines job which isn't
    >> sustainable.
    >>
    >> By putting the heuristics in kernelspace Linux will improve performance also on
    >> workloads the human operator didn't think of as the machine will detect them from
    >> statictical or other behaviour patterns.
    >
    >In order to put the heuristics into kernelspace Linux, I think it
    >necessary to consider the following two points.
    >
    >1) Which cores are tied with the process?
    >This is different from the core on which the process can run. It
    >probably need to combine some CPU resource limit to avoid affecting
    >non-target processes.
    >
    >2) How to derive the value to set in the register?
    >It is necessary to verify whether an appropriate set value can be
    >derived using statistical information, etc. In addition, to prevent
    >the cost of automatic derivation from exceeding the value that would
    >be improved by it.
    >
    >I don't have a prospect for resolving these issues yet. I will
    >continue these considerations.

    Another approach would be to make the set of prefetch settings
    a task attribute. Then set them in the context switch code when
    the process is about to run on a CPU.

    But that assumes you can cheaply change the attributes. If doing
    so requires multiple MSR writes (on x86) it might be a non-starter.

    -Tony
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