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=-1.0 required=5.0 tests=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 87d3bd7b for ; Wed, 26 Jun 2019 19:42:22 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 4B4E39BD9B; Thu, 27 Jun 2019 05:42:21 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 05B8F9BD84; Thu, 27 Jun 2019 05:42:10 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 060A09BD84; Thu, 27 Jun 2019 05:42:09 +1000 (AEST) X-Greylist: delayed 573 seconds by postgrey-1.36 at minnie.tuhs.org; Thu, 27 Jun 2019 05:42:08 AEST Received: from post.cogs.com (post.cogs.com [72.43.6.86]) by minnie.tuhs.org (Postfix) with ESMTPS id 5E9FC9BC77 for ; Thu, 27 Jun 2019 05:42:08 +1000 (AEST) Received: from localhost (localhost [127.0.0.1]) by post.cogs.com (Postfix) with ESMTP id 7EC731021B77D8 for ; Wed, 26 Jun 2019 15:32:34 -0400 (EDT) X-Virus-Scanned: amavisd-new at cogs.com Received: from post.cogs.com ([127.0.0.1]) by localhost (post.cogs.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id pdL1rUcKZXfz for ; Wed, 26 Jun 2019 15:32:33 -0400 (EDT) Received: from rrcs-108-176-86-106.nys.biz.rr.com (rrcs-108-176-86-106.nys.biz.rr.com [108.176.86.106]) by post.cogs.com (Postfix) with ESMTPSA id ACBFE1021B77D2 for ; Wed, 26 Jun 2019 15:32:33 -0400 (EDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3560.7\)) Date: Wed, 26 Jun 2019 15:32:32 -0400 References: <5df8c6f6-2768-4bfb-9c47-3345098078a7@PU1APC01FT048.eop-APC01.prod.protection.outlook.com> <20190625000630.GA7655@mcvoy.com> <20190625003120.GA28608@mit.edu> <20190625004523.GB7655@mcvoy.com> <20190626024503.GA43970@wopr> <20190626025646.GR925@mcvoy.com> <20190626151143.GC3116@mit.edu> <20190626174431.GT925@mcvoy.com> <34DB62C2-7D8C-468B-99E1-CA035C9141A2@eschatologist.net> To: Tuhs In-Reply-To: <34DB62C2-7D8C-468B-99E1-CA035C9141A2@eschatologist.net> Message-Id: <04827B96-5B5E-473E-A95F-67C4292B69D1@cogs.com> X-Mailer: Apple Mail (2.3560.7) 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: , From: Ben Greenfield via TUHS Reply-To: Ben Greenfield Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" > On Jun 26, 2019, at 3:22 PM, Chris Hanson = wrote: >=20 > One thing to remember about Mach is that it really was a *research* = project. Some of the things that have been complained about, e.g. = =E2=80=9Cpointless=E2=80=9D or =E2=80=9Cneedless=E2=80=9D abstraction = and layering, were done specifically to examine the effects of having = those layers of abstraction. Does their presence enable different = approaches to problems? I=E2=80=99m surprised the study of Mach needs any justification. Mach certainly happened and is certainly enjoys a large and growing = installed base. I=E2=80=99m bothered that some feel the need to belittle the interests = of others. I would be more impressed if those criticizing weren=E2=80=99t so = hand-wavy and had more specific points=E2=80=A6. > Do they enable new features altogether? What=E2=80=99s given up by = having them? And so on. >=20 > Just as an example, a lot of the complexity in the Mach VM system = comes from the idea that it could provide a substrate for all sorts of = different types of systems, and it could have all sorts of different = mechanisms underneath supporting it. This means that Mach=E2=80=99s = creators got to do things like try dedicated network virtual memory, = purpose-specific pagers, compressing pagers, etc. You may not need as = much flexibility in a non-research system. >=20 > For another example, Mach did a lot of extra work around things like = processor sets that wouldn=E2=80=99t be needed on (say) a dual-CPU = shared-cache uniform-memory systems, but turns out to be important when = dealing with things like systems with a hierarchy of CPUs, caches, and = memories. Did they know about all the possible needs for that before = they started? >=20 > Having met some of them, the people who created and worked on Mach = were passionate about exploring the space of operating system = architecture and worked to create a system that would be a good vehicle = for that. That wasn=E2=80=99t their only goal=E2=80=94they were also = part of the group creating what was at the time CMU=E2=80=99s = next-generation academic computing environment=E2=80=94but the sum of = their goals generally led to a very pragmatic approach to making things = possible to try while also shipping. >=20 > -- Chris >=20