Re: [PATCH v5] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast

[Steven Rostedt]

On Fri, 9 Jan 2026 11:10:16 -0800
Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:

\> >
> > We also have to consider that migrate disable is *not* cheap at all
> > compared to preempt disable.  
> 
> Looks like your complaint comes from lack of engagement in kernel
> development.

No need to make comments like that. The Linux kernel is an ocean of code.
It's very hard to keep up on everything that is happening. I knew of work
being done on migrate_disable but I didn't know what the impacts of that
work was. Mathieu is still very much involved and engaged in kernel
development.

> migrate_disable _was_ not cheap.
> Try to benchmark it now.
> It's inlined. It's a fraction of extra overhead on top of preempt_disable.

It would be good to have a benchmark of the two. What about fast_srcu? Is
that fast enough to replace the preempt_disable()? If so, then could we
just make this the same for both RT and !RT?

-- Steve