Date: Fri, 26 Oct 2001 14:24:07 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Bakul Shah <bakul@bitblocks.com>, Peter Wemm <peter@wemm.org>, arch@FreeBSD.ORG, Poul-Henning Kamp <phk@critter.freebsd.dk> Subject: Re: 64 bit times revisited.. Message-ID: <XFMail.011026142407.jhb@FreeBSD.org> In-Reply-To: <200110262113.f9QLDBJ38657@apollo.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 26-Oct-01 Matthew Dillon wrote: > >: >: >::> >::> 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. > > And I will also note that trying to represent both seconds and sub-seconds > in a single fixed point integer is a real bad idea. It makes life > unnecessarily difficult for the 95% of the code that only needs the > seconds portion. Any fractional representation should be a SEPARATE > field. Err it is a separate field. You have a 128-bit counter. The high 64-bits are the seconds portion. You just shift to get the seconds. This is not hard. Computers have been good at doing shift right's for quite some time now. -- 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?XFMail.011026142407.jhb>