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Add some tips on benchmarking.

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Add some tips on benchmarking.

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Committed
rafaelMay 24 2017, 9:39 AM
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rL303768: [OPENMP] Allow value of thread local variables in target regions.
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mehdi_amini added inline comments.
/llvm/trunk/docs/Benchmarking.rst
27

Disabling ASLR is a double-edged sword: you may conclude that one version is better than the other while it depends about actual final memory layout. And as such you may reach false conclusion about an optimization or a heuristic.

31

Is this documentation intended to benchmark LLVM itself?
The CMake option here is quite specific, and won't apply to benchmarks in general. It could give the false impression that clang built with this option would perform static linking on a benchmark for example.

40

Missing from the list above: pin the process to a particular CPU, as we don't want the OS to reschedule to another core during the process, and also all cores don't necessarily have the same latency/bandwidth to memory.
Edit: I see this is in the linux specific set of instructions.