Date: Wed, 1 Apr 1998 22:49:09 -0500 (EST) From: Chuck Robey <chuckr@glue.umd.edu> To: John Saunders <john.saunders@scitec.com.au> Cc: "Gregory P. Smith" <greg@nas.nasa.gov>, freebsd-current@FreeBSD.ORG Subject: Re: current-digest V4 #79 Message-ID: <Pine.BSF.3.96.980401224655.299A-100000@localhost> In-Reply-To: <35230829.78DAA808@scitec.com.au>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, 2 Apr 1998, John Saunders wrote: > Gregory P. Smith wrote: > > I think that would violate the Kernel's "never use floating point" rule > > because MMX uses the FP registers. (and on Intel's MMX implementation > > supposedly has a "large" context switch time between MMX and floating > > point mode). > > How does the kernel's "never use floating point" rule co-exist with > the bcopy/bzero/copying/copyout speedups that use the FPU? I've noticed > that the GENERIC config disables the bcopy speedup by using flags 0x1 > but retains the bzero and copyin/out speedups. I've changed my flags > to 0 to enable all speedups and haven't noticed anything bad. > > You are right that the context switch is likely to be a killer, > although it depends on exactly how much the IP checksum can be speeded > up. When the numbers are added up it could be a big win for a server. > I guess the only way to know is to count those clocks. Difference is in using the FP registers only. What you don't want to do in the kernel is *floating*point*operations*, not just use of a register. It's the floating point math that takes ice ages. > > Cheers. > -- +------------------------------------------------------------+ > . | John Saunders mailto:John.Saunders@scitec.com.au (Work) | > ,--_|\ | mailto:john@nlc.net.au (Home) | > / Oz \ | http://www.nlc.net.au/~john/ | > \_,--\_/ | SCITEC LIMITED Phone +61 2 9428 9563 Fax +61 2 9428 9933 | > v | "By the time you make ends meet, they move the ends." | > +------------------------------------------------------------+ > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-current" in the body of the message > > ----------------------------+----------------------------------------------- Chuck Robey | Interests include any kind of voice or data chuckr@glue.umd.edu | communications topic, C programming, and Unix. 213 Lakeside Drive Apt T-1 | Greenbelt, MD 20770 | I run Journey2 and picnic, both FreeBSD (301) 220-2114 | version 3.0 current -- and great FUN! ----------------------------+----------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.3.96.980401224655.299A-100000>