Date: Fri, 26 Oct 2001 13:15:01 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: arch@FreeBSD.ORG, Peter Wemm <peter@wemm.org>, Bakul Shah <bakul@bitblocks.com> Subject: Re: 64 bit times revisited.. Message-ID: <XFMail.011026131501.jhb@FreeBSD.org> In-Reply-To: <6790.1004125611@critter.freebsd.dk>
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On 26-Oct-01 Poul-Henning Kamp wrote: > In message <200110261914.PAA17908@devonshire.cnchost.com>, Bakul Shah writes: > >>> Decimal computers lost the race and they ain't coming back. We want >>> arithmetic on binary computers to be fast and simple. >> >>Most everyone uses powers of ten for timing units. Remember, >>millisecond, microsecond, nanosecond, picosecond?! All test >>equipment time in units of 10s not 2s. That is also why CPUs >>have clock rate in multiples of 10^6 Hzs not 2^20. It is >>just being practical even if division by a power of 10 is a >>bit of a pain. > > If you look in sys/kern/kern_tc.c you can see how much extra > gunk that results in, checking for overruns on the middle part and > whats not. > > There can be no doubt that the best timestamp representation is > pure binary, originating at the second, and that is how my proposal > is constructed: > > <-- 32bit --><-- 32bit --> . <-- 32bit --><-- 32bit --> > 1 2 3 4 IOW, a fixed-point number. This is definitely the optimal solution presented so far for the in-kernel time keeping, IMO. -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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