Re: [PATCH v4 0/6] Add AutoFDO and Propeller support for Clang build

[Nathan Chancellor]

Hi Rong,

On Fri, Oct 18, 2024 at 11:20:02PM -0700, Rong Xu wrote:
> Thanks to all for the feedback and suggestions! We are ready to make any further
> changes needed. Is there anything else we can address for this patch?

I will reply in a separate thread for visibility but I think one of the
biggest open questions at the moment is trying to find someone to
shepherd this code into mainline.

> Also, we know it's not easy to test this patch, but if anyone has had a chance
> to try building AutoFDO/Propeller kernels with it, we'd really appreciate your
> input here. Any confirmation that it works as expected would be very helpful.

I went to take this series for a spin in a virtual machine first as a
smoke test before attempting to boot on bare metal. This was done on a
server with an Intel Xeon Gold 6314U. The kernel booted fine but when I
went to run the command to generate the perf data from the
documentation, I get an error.

  $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c 500009 -o /tmp/perf.data -- make -j$(nproc) O=out mrproper defconfig all
  Error:
  BR_INST_RETIRED.NEAR_TAKEN:k: PMU Hardware or event type doesn't support branch stack sampling.

Do you know if this is expected for a virtual machine setup? I will
attempt to test the series on real hardware here soon, it is currently
tied up with investigating a regression in -next at the moment.

Cheers,
Nathan