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Date: Fri, 24 Jul 2015 17:03:01 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>, Arnaldo Carvalho de Melo <acme@kernel.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
        Stephane Eranian <eranian@google.com>, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH RFC] perf: x86: Improve accuracy of perf/sched clock
Message-ID: <20150724150301.GJ19282@twins.programming.kicks-ass.net>
References: <1437745195-28219-1-git-send-email-adrian.hunter@intel.com>
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On Fri, Jul 24, 2015 at 04:39:55PM +0300, Adrian Hunter wrote:
> @@ -251,17 +253,17 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
>  	rdtscll(tsc_now);
>  	ns_now = cycles_2_ns(tsc_now);
>  
> -	/*
> -	 * Compute a new multiplier as per the above comment and ensure our
> -	 * time function is continuous; see the comment near struct
> -	 * cyc2ns_data.
> -	 */

I'd leave this comment, but update the one this refers to; esp. the bit
that explains why 10.

Also, I think you can remove the definition of CYC2NS_SCALE_FACTOR.

Other than that, seems like a good idea.