linux-kernel - Re: [PATCH] i386 tsc: remove xtime_lock'ing around cpufreq notifier

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Message-Id: <200704122215.04499.ak@suse.de>
Date:	Thu, 12 Apr 2007 22:15:04 +0200
From:	Andi Kleen <ak@...e.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Walker <dwalker@...sta.com>,
	linux-kernel@...r.kernel.org, johnstul@...ibm.com,
	tglx@...utronix.de
Subject: Re: [PATCH] i386 tsc: remove xtime_lock'ing around cpufreq notifier


> They could be huge differences - unbounded, in fact.  It would make
> printk fairly hard to interpret,  I would think.  The only benefit to
> using sched_clock in printk is that if you're using it to work out the
> startup latencies you won't be confused by stolen time.  But I think
> that's a fairly small benefit compared to the disadvantage of not being
> able to meaningfully compare the timestamps on two printk messages.

Ok so the right solution would be a separate printk_clock() that is
implemented as the native sched_clock() even on Xen/VMI.  Should be a SMOP.

-Andi
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