[all-commits] [llvm/llvm-project] 980d66: [llvm-exegesis] Error Out If Perf Counter is Not F...

[Aiden Grossman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 980d66caae62de9b56422a2fdce3f535c2ab325f
      https://github.com/llvm/llvm-project/commit/980d66caae62de9b56422a2fdce3f535c2ab325f
  Author: Aiden Grossman <aidengrossman at google.com>
  Date:   2025-03-31 (Mon, 31 Mar 2025)

  Changed paths:
    M llvm/tools/llvm-exegesis/lib/Error.cpp
    M llvm/tools/llvm-exegesis/lib/Error.h
    M llvm/tools/llvm-exegesis/lib/PerfHelper.cpp

  Log Message:
  -----------
  [llvm-exegesis] Error Out If Perf Counter is Not Fully Enabled (#132892)

Perf counters can be multiplexed if there are too many that need to be
scheduled on a core at the same time (and they exceed the available
PMUs). Other processes (especially system ones in certain environments,
not commonly on Desktop Linux from what I've seen) can also interfere.
This will impact the measurement fidelity as the counter is not actually
counting cycles/uops the entire time. This patch makes it so that we
error out in these cases so the user gets a visible indication things
have gone wrong rather than things failing silently.



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