From owner-freebsd-current Wed Apr 1 19:50:10 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id TAA07421 for freebsd-current-outgoing; Wed, 1 Apr 1998 19:50:10 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from picnic.mat.net (picnic.mat.net [206.246.122.117]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id TAA07416 for ; Wed, 1 Apr 1998 19:50:05 -0800 (PST) (envelope-from chuckr@glue.umd.edu) Received: from localhost (chuckr@localhost) by picnic.mat.net (8.8.8/8.8.5) with SMTP id WAA00420; Wed, 1 Apr 1998 22:49:09 -0500 (EST) Date: Wed, 1 Apr 1998 22:49:09 -0500 (EST) From: Chuck Robey X-Sender: chuckr@localhost To: John Saunders cc: "Gregory P. Smith" , freebsd-current@FreeBSD.ORG Subject: Re: current-digest V4 #79 In-Reply-To: <35230829.78DAA808@scitec.com.au> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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