[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.

0 files changed, 0 insertions, 0 deletions