Date: Tue, 1 Nov 2005 08:02:02 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: phk@phk.freebsd.dk, freebsd-current@freebsd.org Subject: Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?) Message-ID: <20051101080018.R18382@fledge.watson.org> In-Reply-To: <20051031.215329.115777034.imp@bsdimp.com> References: <4365EF7B.1020706@freebsd.org> <81213.1130754398@critter.freebsd.dk> <20051031.215329.115777034.imp@bsdimp.com>
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On Mon, 31 Oct 2005, M. Warner Losh wrote: > In message: <81213.1130754398@critter.freebsd.dk> > "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes: > : I am going to insist that clock_gettime(CLOCK_REALTIME, CLOCK_UPTIME) > : remain precise. > > 1ms is way too imprecise for the stuff we do at work. We need 3-4 more > orders of magnitude at a minimum from the time keeping system. Ideally, > through well documented interfaces. While I agree that for many consumers, sub-1ms accuracy is too low, I suggest that as a vendor of atomic clocks, your company is in fact not the average consumer of timing information. :-). One nice thing about the Linux TSC model, despite its limitations, is that it provides a middle ground between incrementing the clock in ticks and providing a more continuous measure of time, by allowing interpolation between ticks. Robert N M Watson
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