From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from minnie.tuhs.org (minnie.tuhs.org [45.79.103.53]) by inbox.vuxu.org (OpenSMTPD) with ESMTP id 001867e7 for ; Sun, 23 Jun 2019 22:09:26 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 2D1329BC99; Mon, 24 Jun 2019 08:09:25 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id F39B19BC4C; Mon, 24 Jun 2019 08:09:00 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id CA2229BC4C; Mon, 24 Jun 2019 08:08:57 +1000 (AEST) Received: from mercury.lcs.mit.edu (mercury.lcs.mit.edu [18.26.0.122]) by minnie.tuhs.org (Postfix) with ESMTPS id 8410C9BC49 for ; Mon, 24 Jun 2019 08:08:57 +1000 (AEST) Received: by mercury.lcs.mit.edu (Postfix, from userid 11178) id AADD018C0CF; Sun, 23 Jun 2019 18:08:56 -0400 (EDT) To: tuhs@minnie.tuhs.org Message-Id: <20190623220856.AADD018C0CF@mercury.lcs.mit.edu> Date: Sun, 23 Jun 2019 18:08:56 -0400 (EDT) From: jnc@mercury.lcs.mit.edu (Noel Chiappa) Subject: Re: [TUHS] CMU Mach sources? 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: jnc@mercury.lcs.mit.edu Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" > From: Andrew Warkentin > Mach and the other kernels influenced by it basically destroyed the > reputation of microkernels ... a simple read() of a disk file, which is > a single kernel call on a monolithic kernel and usually two context > switches on QNX, takes at least 8 context switches - client->VFS->disk > FS->partition driver->disk driver and back again). Hammer-nail syndrome. When the only tool you have for creating separate subsystems is processes, you wind up with a lot of processes. Who'd a thunk it. A system with a segmented memory which allows subroutine calls from one subsystem to another will have a lot less overhead. It does take hardware support to be really efficient, though. The x86 processors had that support, until Intel dropped it from the latest ones because nobody used it. Excuse me while I go bang my head on a very hard wall until the pain stops. Noel