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
___
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
