Re: [Xen-devel] [PATCH 00/15] xen/tools: add tracing to various Xen subsystems

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Wed, 2017-06-07 at 10:13 -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Jun 01, 2017 at 07:33:33PM +0200, Dario Faggioli wrote:
> > 
> > Patch 5 deserves special mention. In fact, now that we have
> > Kconfig, I thought
> > it could be a nice thing to make it possible to select, at build
> > config time,
> > whether we want tracing or not, in the hypervisor (like, for
> > instance, we do
> > for performance counters).
> 
> Did you have thoughts on perhaps using asm goto as an
> alterantive to unlikely?
> 
> In Linux it is called jump labels or such - the idea is that the 
> code has (by default and on x86) five NOP instructions. But you
> can patch it over and add an call to the unlikely code.
> 
Yes, I know. I've never actually looked at the code, but I know they do
that, and I think it's cool.

> But perhaps that is more of an future idea as looking at the Linux
> code
> it looks quite large and not that simple.
> 
I would love for us to do something similar in Xen. I've _thought_
about that many times, but that's it. :-/

Let's see... right now, I can't look into this, as I agree with you
that it would be a major piece of work.

But yes, it's been in my thoughts! :-)

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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