From owner-freebsd-hackers Tue Oct 24 11:41:37 1995 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.6.12/8.6.6) id LAA25642 for hackers-outgoing; Tue, 24 Oct 1995 11:41:37 -0700 Received: from etinc.com (etinc-gw.new-york.net [165.254.13.209]) by freefall.freebsd.org (8.6.12/8.6.6) with ESMTP id LAA25629 for ; Tue, 24 Oct 1995 11:41:32 -0700 Received: from trumpet.etnet.com (trumpet.etnet.com [129.45.17.35]) by etinc.com (8.6.11/8.6.9) with SMTP id OAA00819; Tue, 24 Oct 1995 14:44:10 -0400 Date: Tue, 24 Oct 1995 14:44:10 -0400 Message-Id: <199510241844.OAA00819@etinc.com> X-Sender: dennis@etinc.com X-Mailer: Windows Eudora Version 2.0.3 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: Bruce Evans From: dennis@etinc.com (dennis) Subject: Re: Async utilization..... Cc: hackers@freebsd.org Sender: owner-hackers@freebsd.org Precedence: bulk >>>How much less efficient? For logins, even a local ethernet is only a few >>>times more efficient than 115200 bps async through a 16450. This is >>>mostly because the pty implementation is poor. > >>Your numbers, like unix utilization >>and timing numbers, are garbage. Set up a controlled test where you know the >>answer >>and the numbers won't be close. > >FreeBSD isn't unix. The sum of the user, system and interrupt times is >accurate to within 5usec * (number of context switches) under FreeBSD, >but since the interrupt time is not available through any syscall and >my tests involve a lot of interrupts, I just used the real time, which >is accurate to about 1 part in 1000 here. > Its not a real measurement, so you can't use it. Period. Figure out the processing requirement for handling one average frame size of bytes with a 16450 with 8-bit I/O cycles and loads of interrupts, add 20% and compare it to a single interrupt and one 16-bit bus transfer per frame. It doesn't take a rocket scientist to know there's a signficant difference in processing requirements. Dennis ---------------------------------------------------------------------------- Emerging Technologies, Inc. http://www.etinc.com Synchronous Communications Cards and Routers For Discriminating Tastes. 56k to T1 and beyond. Frame Relay, PPP, HDLC, and X.25