linux-kernel - Re: [PATCH 1/3] tracing: Merge irqflags + preempt counter.

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Date:   Mon, 25 Jan 2021 20:52:28 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/3] tracing: Merge irqflags + preempt counter.

On 2021-01-25 14:03:23 [-0500], Steven Rostedt wrote:
> 
> I was thinking about the inlining for two reasons. One was to consolidate
> the logic in the header file, as they are small functions. And two, inlined
> functions tend to be faster than non-inlined functions. Thus, I wasn't
> looking at this from a size point of view, but since this is called by all
> events, including function tracer, being efficient is a requirement.

In the ftrace_syscall_enter() example I made, flags were not evaluated
three times but only once. This should do more in terms of performance
compare to simply inline it.

> > I can post the irqflags-merge and the inlinining as two seprate patches
> > and you can then decide if you merge the two patches or drop the
> > inlining.
> 
> Feel free to send it as separate patches. I'd like to have the inlining.

Just sent as an extra patch. In case you have a benchmark, I'm curious
;)

> Thanks!
> 
> -- Steve

Sebastian