[lttng-dev] lttng-ust on arm64 getting bogged down by the getcpu syscall (taking more than 600ns per call)

[Akhil Veeraghanta]

Hello!

I've run into an issue with getcpu not having a vsdo implementation and taking anywhere from 600ns to 80us (avg 1 us) when using lttng-ust tracepoints.
I am on lttng v2.13 and kernel version 4.9.253-l4t, running on a jetson (arm64). I was digging around and found that rseq might be the recommended next step

I am wondering:

  1.  Are there examples of using rseq system call to replace getcpu
  2.  Are there any existing patches that I can apply to get better getcpu performance

Thanks in advance,
Akhil
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