On 11 November 2016 at 08:32, Sebastian Pop sebpop@gmail.com wrote:

Salut Matthieu,

Bon matin,

I was following your patches to enable ETM support in the linux kernel last years, and I have just seen that you have a very nice blog on how to use perf record to gather execution traces.

Depending on the source you have read the information may be outdated. Nowadays the very latest instructions can be found in the HOWTO.md on the OpenCSD repository [1]. That documentation is maintained regularly and is considered accurate.

[1]. https://github.com/Linaro/OpenCSD/tree/opencsd-0v003

I am mainly interested to use this mechanism to enable collection of traces with "perf record -b" like Intel's Last Branch Record: this is used by AutoFDO in the compiler to know which code paths are hot and enable better inlining, register allocation, and code layout: http://research.google.com/pubs/pub45290.html

This looks interesting.

I am interested to work with you to enable "perf record -b" on aarch64.

This is a sizeable project that will keep you occupied for a little while :o) I am happy to give guidance and review patches. Some people on the CoreSight mailing list (CC'ed here) are very proficient with the CoreSight tracers and can help understand the more complex features of the IP. I suggest CC'ing the list if/when you have questions.

Best regards, Mathieu

Thanks, Sebastian