Date: Sun, 30 Oct 2005 11:59:36 -0800 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Scott Long <scottl@samsco.org> Cc: Alexander Leidinger <Alexander@Leidinger.net>, freebsd-current@freebsd.org, David Xu <davidxu@freebsd.org> Subject: Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?) Message-ID: <20051030195936.GZ4115@funkthat.com> In-Reply-To: <4364D90F.3090205@samsco.org> References: <30595.1130493297@critter.freebsd.dk> <20051028153457.d0wqgn2ask4sgw4k@netchild.homeip.net> <20051029195703.GB39253@dragon.NUXI.org> <43646AAC.2080107@freebsd.org> <20051030093718.GE39253@dragon.NUXI.org> <4364D90F.3090205@samsco.org>
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Scott Long wrote this message on Sun, Oct 30, 2005 at 07:30 -0700:
> >Correct, but why is it felt the latency of the ACPI timer is an issue?
> >Of course we all want things to as fast as possible, but is that just an
> >abstract desire, or a real issue was run into?
> >
>
> ACPI-fast requires an ioport read which takes about 1us (according to
> Google). Do that 1000 times a second and you have each CPU spending
> 1% of its time doing nothing but reading the clock. Yikes.
Math correction: .1%... 1us * 1000 = 1ms, 1ms = .001s, .001 * 100% = .1%
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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