linux-kernel - Re: [BUG] perf: perf sched warning possibly due to clock granularity on AMD

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Date:	Mon, 06 Feb 2012 21:31:33 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Borislav Petkov <bp@...64.org>
Cc:	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, acme@...hat.com, mingo@...e.hu,
	robert.richter@....com, eric.dumazet@...il.com,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: Re: [BUG] perf: perf sched warning possibly due to clock
 granularity on AMD

On Mon, 2012-02-06 at 21:27 +0100, Borislav Petkov wrote:
> On Mon, Feb 06, 2012 at 05:54:19PM +0100, Peter Zijlstra wrote:
> > On Mon, 2012-02-06 at 17:46 +0100, Borislav Petkov wrote:
> > > > across all CPUs in the entire system.
> > > 
> > > Right, by the "entire system" you mean consistent across cores and
> > > sockets but not necessarily across cabinets, as in the comment above,
> > > correct?
> > > 
> > > If so, let me ask around if this holds true too.
> > 
> > Every CPU available to the kernel. So if you run a single system image
> > across your cabinets, then yes those too.
> 
> Ok, but what about that sentence "(but not across cabinets - we turn
> it off in that case explicitly.)" - I don't see any place where it is
> turned off explicitly... Maybe a stale comment?

I suspect it might be the sched_clock_stable = 0 in mark_tsc_unstable(),
but lets ask Venki, IIRC he wrote all that.

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