linux-kernel - Re: Performance overhead of get_cycles

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Message-ID: <20071211201930.GB22397@elte.hu>
Date:	Tue, 11 Dec 2007 21:19:30 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Performance overhead of get_cycles_sync


* Andi Kleen <ak@...e.de> wrote:

> Ingo Molnar <mingo-X9Un+BFzKDI@...lic.gmane.org> writes:
> 
> > the TSC clocksource (and hence the vsyscall code) is turned off on 
> > systems that fail the TOD/CLOCK portion of this test:
> 
> Which is not on core2 which was the question about. And if it was 
> turned off it wouldn't use get_cycles_sync() at all.

it is turned off on core2 too:

 # cat /sys/devices/system/clocksource/clocksource0/current_clocksource
 acpi_pm

	Ingo
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