From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 15792 invoked from network); 16 Jul 2021 15:44:54 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 16 Jul 2021 15:44:54 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id 0A5CA9C7FC; Sat, 17 Jul 2021 01:44:52 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 523C69C7F1; Sat, 17 Jul 2021 01:44:36 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 2E00D9C7F1; Sat, 17 Jul 2021 01:44:34 +1000 (AEST) Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by minnie.tuhs.org (Postfix) with ESMTPS id 937B29C7F0 for ; Sat, 17 Jul 2021 01:44:33 +1000 (AEST) Received: from callcc.thunk.org (96-65-121-81-static.hfc.comcastbusiness.net [96.65.121.81]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 16GFiQRn029569 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 16 Jul 2021 11:44:27 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 7B7F04202F5; Fri, 16 Jul 2021 11:44:26 -0400 (EDT) Date: Fri, 16 Jul 2021 11:44:26 -0400 From: "Theodore Y. Ts'o" To: Clem Cole Message-ID: References: <213a4c11-3ab2-4b4a-8d6b-b52105a19711@localhost> <5777F7E6-062B-4C5A-9C98-36FFE6AC3414@stdio.com> <20210716135639.GI12733@mcvoy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [TUHS] 386BSD released X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: The Eunuchs Hysterical Society , Bakul Shah Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" On Fri, Jul 16, 2021 at 10:40:56AM -0400, Clem Cole wrote: > > A huge difference, as Ted I'm sure knows, is that you tended to have many > more serial lines than network interfaces. I suspect Rob's scheme > would have sucked trying to support traditional single-byte serial > interfaces or really just use too much memory to be practical. Network interfaces tend to be much faster than serial lines; at least an order of magnitude. And with network interfaces you care about the packet boundaries, and you want to process each packet separately. So that makes things a lot harder than with serial interfaces. With serial ports, 8k per serial port is plenty (2 x 2k flip buffers, plus a 4k tty buffer between the mid-layer and userspace) for the receive path. On the PDP-11, memory was much more constrained, so the clist with each cblock storing 6 characters at a time in a linked list was probably necessary. But even in the early days of the 386, you could afford to make a different memory/performance tradeoff. - Ted