linux-kernel - Re: [PATCH] ring-buffer: Use a housekeeping CPU to wake up waiters

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Message-ID: <20260109175423.70ba42d7@mordecai>
Date: Fri, 9 Jan 2026 17:54:23 +0100
From: Petr Tesarik <ptesarik@...e.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Sebastian Andrzej Siewior
 <bigeasy@...utronix.de>, Clark Williams <clrkwllms@...nel.org>,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 linux-rt-devel@...ts.linux.dev
Subject: Re: [PATCH] ring-buffer: Use a housekeeping CPU to wake up waiters

On Fri, 9 Jan 2026 11:15:06 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 9 Jan 2026 09:57:56 +0100
> Petr Tesarik <ptesarik@...e.com> wrote:
> 
> > I have removed both "inline" and "noinline" in v2, leaving it at the
> > discretion of the compiler. If you believe it deserves a "noinline",
> > feel free to add it. FWIW on x86-64, I didn't observe any measurable
> > diference either in latency or instruction cache footprint.  
> 
> Please add the noinline. I went through and added strategic "noinline" and
> "__always_inline", as well as placing "likely()" and "unlikely()" and
> dropped the cost of adding an event from just under 300ns down to less than
> 150ns.
> 
> This code is called during function tracing (hit at every function call),
> and yes, every little bit helps!

I'm going to wait a few days for further comments, then add it in v3.

Thanks for your time!

Petr T