Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chainsupport to use NMI-safe methods

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> > To a point where it cannot afford a simple register save/restore 
> > ?
> > 
> > There is "caring" and "_caring_". I am tempted to ask what NMI 
> > handler execution frequency you have in mind here to figure out 
> > if we are not trying to optimize sub-nanoseconds per minutes. ;)
> 
> I routinely run 'perf' with half a million NMIs per second or 
> more. ( Why wait 10 seconds for a profile you can get in 1 second? 
> ;-)
> 
> Granted that is over multiple CPUs - but still performance does 
> matter here too.
> 
> Reading cr2 is certainly fast. Writing it - dunno.

But one thing is sure: it is certainly going to be faster than the 
INVLPG(s!) we have to do with the GUP solution.

	Ingo
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