Date: Sat, 4 Nov 2000 07:27:39 +1300 From: Joerg Micheel <joerg@cs.waikato.ac.nz> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Zhiui Zhang <zzhang@cs.binghamton.edu>, freebsd-hackers@freebsd.org, joerg@cs.waikato.ac.nz Subject: Re: granularity of gettimeofday() Message-ID: <20001104072739.K26626@cs.waikato.ac.nz> In-Reply-To: <1581.973275681@critter>; from phk@critter.freebsd.dk on Fri, Nov 03, 2000 at 07:21:21PM %2B0100 References: <Pine.SOL.4.21.0011031255360.118-100000@jade> <1581.973275681@critter>
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On Fri, Nov 03, 2000 at 07:21:21PM +0100, Poul-Henning Kamp wrote: > The long answer is: FreeBSD can deliver time with a resolution of > 1/2^32 nanosecond = 232.8E-21 seconds. The actual resolution is > much worse, because the hardware usually doesn't provide any better > than about a nanosecond at best these days. On certain hardware > only about a microsecond of actual resolution is available. Why could't gettimeofday be tuned to provide nanosecond resolution in reality, with the assistance of the TSC register ? I understand this does not work on a 486, but that's not the platform people ask for such a resolution. With every celeron today exceeding 300 MHz, 3 nanoseconds is a reality. Of course, there will be syscall overhead, understood. Joerg -- Joerg B. Micheel Email: <joerg@cs.waikato.ac.nz> WAND and NLANR MOAT Email: <joerg@nlanr.net> The University of Waikato, CompScience Phone: +64 7 8384794 Private Bag 3105 Fax: +64 7 8585095 Hamilton, New Zealand Plan: PMA, TINE and the DAG's To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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