On Fri, 29 Aug 2025 at 16:09, Steven Rostedt [off-list ref] wrote:

Perf does do things differently, as I believe it processes the events as it
reads from the kernel (Arnaldo correct me if I'm wrong).

For the tracefs code, the raw data gets saved directly into a file, and the
processing happens after the fact. If a tool is recording, it still needs a
way to know what those hash values mean, after the tracing is complete.

But the data IS ALL THERE.

Really. That's the point.

It's there in the same file, it just needs those mmap events that
whoever pasrses it - whether it be perf, or somebody reading some
tracefs code - sees the mmap data, sees the cookies (hash values) that
implies, and then matches those cookies with the subsequent trace
entry cookies.

But what it does *NOT* need is munmap() events.

What it does *NOT* need is translating each hash value for each entry
by the kernel, when whoever treads the file can just remember and
re-create it in user space.

I'm done arguing. You're not listening, so I'll just let you know that
I'm not pulling garbage. I've had enough garbage in tracefs, I'm still
smarting from having to fix up the horrendous VFS interfaces, I'm not
going to pull anything that messes up this too.

        Linus