From owner-freebsd-hackers Wed Jan 10 19:34:56 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id TAA25552 for hackers-outgoing; Wed, 10 Jan 1996 19:34:56 -0800 (PST) Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id TAA25545 for ; Wed, 10 Jan 1996 19:34:50 -0800 (PST) Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id UAA16458; Wed, 10 Jan 1996 20:27:42 -0700 From: Terry Lambert Message-Id: <199601110327.UAA16458@phaeton.artisoft.com> Subject: Re: pppd vs ijppp To: dennis@etinc.com (dennis) Date: Wed, 10 Jan 1996 20:27:42 -0700 (MST) Cc: pb@fasterix.freenix.fr, hackers@freebsd.org In-Reply-To: <199601110013.TAA00308@etinc.com> from "dennis" at Jan 10, 96 07:13:38 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hackers@freebsd.org Precedence: bulk Geeze, Dennis, and I usually agree with you because of your customer perspective... > A good example is the routing function, which is in the kernel because its > too damn inefficient in user space. PPP routing is a matter of poll retention time vs. transmissability, since the interface PPP uses is generally several orders of magnitude slower than that which it routes to/from. What we are talking about adding is some propagation delay, and even then, it will be on the basis of system loading and user load (which may be zero) that determines if a context switch will actually be to anything other than the idle process. And if it's not, the majority of the protection domain crossing overhead is in the copy in/out, and that's recoverable based on implementation (see previous posting). > Mr kendals example of "lets move tcp out of the kernel" was a good > analogy to the kind of arguments we're getting on this thread. It's not as stupid as it sounds. There are some sound technical reasons why you might want to do this, and if you used mapping tricks (or better, page protection via page anonymity), you might even get better performance out of your applications. I leave you to rummage papers on the topic from ftp.sage.usenix.org. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.