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=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 24f55f6d for ; Wed, 26 Jun 2019 19:23:12 +0000 (UTC) Received: by minnie.tuhs.org (Postfix, from userid 112) id 78FEF9BF97; Thu, 27 Jun 2019 05:23:11 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 9D4839BC77; Thu, 27 Jun 2019 05:22:52 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=pass (1024-bit key; unprotected) header.d=eschatologist.net header.i=@eschatologist.net header.b="nv1Lpw5/"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 686E89BD84; Thu, 27 Jun 2019 05:22:50 +1000 (AEST) X-Greylist: delayed 90282 seconds by postgrey-1.36 at minnie.tuhs.org; Thu, 27 Jun 2019 05:22:49 AEST Received: from blue.elm.relay.mailchannels.net (blue.elm.relay.mailchannels.net [23.83.212.20]) by minnie.tuhs.org (Postfix) with ESMTPS id 303899BC77 for ; Thu, 27 Jun 2019 05:22:49 +1000 (AEST) X-Sender-Id: dreamhost|x-authsender|cmhanson@eschatologist.net Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 74EAA5E141F for ; Wed, 26 Jun 2019 19:22:48 +0000 (UTC) Received: from pdx1-sub0-mail-a10.g.dreamhost.com (100-96-91-148.trex.outbound.svc.cluster.local [100.96.91.148]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id E25B35E1D51 for ; Wed, 26 Jun 2019 19:22:47 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|cmhanson@eschatologist.net Received: from pdx1-sub0-mail-a10.g.dreamhost.com ([TEMPUNAVAIL]. [64.90.62.162]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384) by 0.0.0.0:2500 (trex/5.17.2); Wed, 26 Jun 2019 19:22:48 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|cmhanson@eschatologist.net X-MailChannels-Auth-Id: dreamhost X-Reaction-Harmony: 4b1977da187b6cfb_1561576968245_2194663666 X-MC-Loop-Signature: 1561576968245:4233534616 X-MC-Ingress-Time: 1561576968245 Received: from pdx1-sub0-mail-a10.g.dreamhost.com (localhost [127.0.0.1]) by pdx1-sub0-mail-a10.g.dreamhost.com (Postfix) with ESMTP id 83CEA83A8B for ; Wed, 26 Jun 2019 12:22:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=eschatologist.net; h=from :content-type:content-transfer-encoding:mime-version:subject :date:references:to:in-reply-to:message-id; s=eschatologist.net; bh=5WeorjxMQNBvg3moajFz3HsHQ94=; b=nv1Lpw5/jzfrio9MWwH7nZloQCJO 66VfSld2VJETCzGEV+8D4woDA3GErEusNWeeoH1xGkqtxXh98ddulrgWoq68M1LE E15xskJyP852grlxi+e18gvJK4yIFGpokdyRY4cp83hKwJllk4jpxjzs8KfaiPKh aV3nUMo6ft/MQ7A= Received: from [10.0.1.206] (c-76-126-113-109.hsd1.ca.comcast.net [76.126.113.109]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: cmhanson@eschatologist.net) by pdx1-sub0-mail-a10.g.dreamhost.com (Postfix) with ESMTPSA id 4FBD883A86 for ; Wed, 26 Jun 2019 12:22:44 -0700 (PDT) X-DH-BACKEND: pdx1-sub0-mail-a10 From: Chris Hanson Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Date: Wed, 26 Jun 2019 12:22:42 -0700 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> To: Tuhs In-Reply-To: <20190626174431.GT925@mcvoy.com> Message-Id: <34DB62C2-7D8C-468B-99E1-CA035C9141A2@eschatologist.net> X-Mailer: Apple Mail (2.3445.104.11) X-VR-OUT-STATUS: OK X-VR-OUT-SCORE: 0 X-VR-OUT-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgeduvddrudeigddugeduucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuggftfghnshhusghstghrihgsvgdpffftgfetoffjqffuvfenuceurghilhhouhhtmecufedttdenucenucfjughrpefhtgfgggfuffhfvfgjkffosehtqhhmtdhhtdejnecuhfhrohhmpeevhhhrihhsucfjrghnshhonhcuoegtmhhhrghnshhonhesvghstghhrghtohhlohhgihhsthdrnhgvtheqnecukfhppeejiedruddviedruddufedruddtleenucfrrghrrghmpehmohguvgepshhmthhppdhhvghloheplgdutddrtddruddrvddtiegnpdhinhgvthepjeeirdduvdeirdduudefrddutdelpdhrvghtuhhrnhdqphgrthhhpeevhhhrihhsucfjrghnshhonhcuoegtmhhhrghnshhonhesvghstghhrghtohhlohhgihhsthdrnhgvtheqpdhmrghilhhfrhhomheptghmhhgrnhhsohhnsegvshgthhgrthholhhoghhishhtrdhnvghtpdhnrhgtphhtthhopehtuhhhshesmhhinhhnihgvrdhtuhhhshdrohhrghenucevlhhushhtvghrufhiiigvpedt 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: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" 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? Do they enable new features altogether? What=E2=80= =99s given up by having them? And so on. 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. 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? 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. -- Chris