Re: [Xen-devel] [PATCH] x86 fixes for 3.3 impacting distros (v1).

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Feb 20, 2012 at 08:01:43PM -0500, Steven Rostedt wrote:
> On Fri, 2012-02-10 at 10:34 -0500, Konrad Rzeszutek Wilk wrote:
> >    66 66 66 90              data32 data32 xchg %ax,%ax
> > 
> > [the 66 66 .. is 'nop']. Looks good right? Well, it does work very well on 
> > Intel
> > (used an i3 2100), but on AMD A8-3850 it hits a performance wall - that I 
> > found out
> > is a result of CONFIG_FUNCTION_TRACER (too many nops??) being compiled in 
> > (but the tracer
> > is set to the default 'nop'). If I disable that specific config option the 
> > numbers
> > are the same as the baseline (with CONFIG_FUNCTION_TRACER disabled) on the 
> > AMD box.
> > Interestingly enough I only see these on AMD machines - not on the Intel 
> > ones.
> 
> All paravirt ops should be labeled with "notrace" so that function
> tracer does not trace those functions. Have you annotated your new
> paravirt ops with notrace?

No. I hadn't realized that flag existed until your email a couple of days ago - 
I hadn't
had a chance to see if the notrace would solve this. But let me do that and get
back on this.

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