Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86

[Peter Zijlstra]

On Mon, May 22, 2017 at 02:03:21PM +0200, Peter Zijlstra wrote:
> On Fri, May 19, 2017 at 10:06:22AM -0700, kan.liang@xxxxxxxxx wrote:
> > This patch was once merged, but reverted later.
> > Because ref-cycles can not be used anymore when watchdog is enabled.
> > The commit is 44530d588e142a96cf0cd345a7cb8911c4f88720
> > 
> > The patch 1/2 has extended the ref-cycles to GP counter. The concern
> > should be gone.
> 
> So its not a problem if every Atom prior to Goldmont, and all Core/Core2
> products regress?
> 
> P6 and P4 you've entirely broken, as they don't have REF_CPU_CYCLES at all.

 + KNC

> 
> So no, I don't think this is right even now.
> 
>