Hi, I think the first problem you will run into is that rseq is only available on kernels 4.18+. As far as I know, starting with glibc 2.35, getcpu() defers to using rseq when available. Is there a way you can upgrade these two components and see if the overhead is reduced? Jérémie -- Jérémie Galarneau EfficiOS Inc. https://www.efficios.com ________________________________ From: lttng-dev on behalf of Akhil Veeraghanta via lttng-dev Sent: October 11, 2022 16:57 To: lttng-dev@lists.lttng.org Subject: [lttng-dev] lttng-ust on arm64 getting bogged down by the getcpu syscall (taking more than 600ns per call) 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