Re: [PATCH v2] rtla/timerlat: Lock the memory of the user-space threads

[John Ogness <john.ogness@linutronix.de>]

On 2026-11-13, Tomas Glozar <tglozar@redhat.com> wrote:
> The only other activities the user thread performs with RT priority on
> before entering the timerlat interface read loop are setting the
> cgroup and opening the timerlat interface file descriptor. I agree
> that ideally, setting the priority should be done just before the
> loop.

If you say it is ideal to do X, then why not do X? Real-time tasks
(especially running at rtprio 95!) need to respect other real-time tasks
on the system. Developers new to RT might see this code and copy it. The
code even has a comment:

"If you want to use as base for your own tool... go ahead."

For me there are two issues here:

1. RT latency measurement tooling needs to be a little intrusive to a
system as practical. Otherwise it may not be possible for developers to
use the tooling on their real environment.

2. Official RT tooling should set the example of how to program for RT
Linux correctly.

John