linux-kernel - Re: [RFC PATCHSET] sched,perf: unify tracers in sched and move perf on top of TP

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Date:	Thu, 06 May 2010 09:04:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Tejun Heo <tj@...nel.org>, efault@....de, avi@...hat.com,
	paulus@...ba.org, acme@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCHSET] sched,perf: unify tracers in sched and move
 perf on top of TP

On Thu, 2010-05-06 at 08:31 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Well, I'd much rather just see a direct call in the code than having to 
> > reverse engineer wth hangs onto that _EVENT() junk.
> 
> Direct calls into code were fine 10 years ago, but since then we got:
> 
>  - preempt notifiers

Are per task an no good for driving perf.

>  - sw events
>  - tracepoints

Are unrelated to the core perf scheduler calls.

> Which add up to a lot more than just a plain call into code.
> 
> Also, with the jump-optimizations we will have tracepoints that are _cheaper_ 
> than a plain function call.

Which can just as easily be used on the core perf hooks.

> > Also, we don't need ABI muck for this.
> 
> we already have an ABIs in place here - this would just properly unify and 
> enumerate it.

I'm not getting it, this is about in-kernel stuff, there are _NO_ in
kernel ABIs.
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