InstructionOverhead

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Description

The pattern "Instruction Overhead" describes the fact that for a piece of high-level code, the compiler outputs a lot of instructions although is could be done in less. One common example are non-vectorized instructions.


Symptoms

Instruction Overhead causes a low application performance and a good scaling behavior across cores. The performance is insensitive to the problem size.


Detection

  • Low CPI value (near to theoretical limit)
  • Large non-FP instruction count (constant vs. number of cores)


Possible optimizations and/or fixes

It depends on the kind of instructions. If the code is using scalar FP instructions, activate vectorization to reduce the number of instructions.


Applicable applications or algorithms or kernels