[dragontamer]

On AMD systems, many hardware performance counters are locked behind BIOS flags/configuration.

I admit that I don't know how Intel works, but disabling the use of these performance-counters at startup should be sufficient for any potential security problem.

I'd expect that only development boxes (maybe staging?) would be interested in performance counters anyway. Maybe the occasional development box could be setup for performance-sampling and collecting these counters, but not all production boxes need to be run with performance-counters on.

[mhh__]

No I want these performance counters everywhere. Obviously I know they can be disabled but that doesn't really help.

I also really want them in CI but that might be a long way away.

[dman]

Being able to collect performance data from production boxes is invaluable.

[jeffbee]

Yes, getting LBR data from production workloads is the whole ballgame for AutoFDO/SamplePGO and BOLT/Propeller. You cannot access the LBR on any EC2 machine short of a "metal" instance.

[mhh__]

When it comes to PGO (vs. profiling the whole system) though it's worth noting that a lot of the speedup comes from things which are too trivial for us humans to consider.

When I profiled the D compiler with and without PGO enabled it became obvious that a lot of the speedup of PGO basically comes just from running the program, the choice of testcases made almost no difference.

[aseipp]

> not all production boxes need to be run with performance-counters on.

Production is exactly the place where you want full performance counter support, all the time, everywhere, on every machine.