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, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 7023 invoked from network); 9 Apr 2022 12:17:59 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 9 Apr 2022 12:17:59 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id B8C989D70A; Sat, 9 Apr 2022 22:17:53 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 4DE6C9D680; Sat, 9 Apr 2022 22:17:24 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id B286F9D680; Sat, 9 Apr 2022 22:15:48 +1000 (AEST) X-Greylist: delayed 323 seconds by postgrey-1.36 at minnie.tuhs.org; Sat, 09 Apr 2022 22:15:48 AEST Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by minnie.tuhs.org (Postfix) with ESMTPS id 2BB0D9D665 for ; Sat, 9 Apr 2022 22:15:48 +1000 (AEST) Received: from penguin.thunk.org (8-19-56-94.hwccustomers.com [8.19.56.94] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 239CAMWA028882 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 9 Apr 2022 08:10:23 -0400 Received: by penguin.thunk.org (Postfix, from userid 1000) id BF0D517AC4; Sat, 9 Apr 2022 08:10:21 -0400 (EDT) Date: Sat, 9 Apr 2022 08:10:21 -0400 From: tytso To: The Unix Heritage Society mailing list Message-ID: References: <7wh774dtvi.fsf@junk.nocrew.org> <20220408152834.GE29186@mcvoy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [TUHS] Interesting commentary on Unix from Multicians. 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" On Fri, Apr 08, 2022 at 02:02:23PM -0700, Greg A. Woods wrote: > Single Level Storage is an awesome concept and removes so many ugly > hacks from algorithms that otherwise have to process data in files. > Doing data processing with read and write and pipes is effectively > working through a straw whereas SLS allows all (reasonably sized) data > to be presented in entirely complete randomly accessible arrays just by > attaching a "file" to a segment. Mmap() is a very poor replacement that > requires a great deal extra bookkeeping that's next to impossible to > hide from; and also there's the problem of the consistency semantics > being different between the I/O based filesystems and direct memory > mapping of their files, which Mmap() reveals, and which SLS eliminates > (by simply not having any I/O mechanism for files in the first place!). To be fair, Multics had it a lot easier, because core memory meant that every single memory access could be considered "durable storage", so there was no real need for "fsync(2)" or "msync(2)". So I/O consistency could be done much like writing to persistent memory, except that there would be no need for "CLFLUSH" (Who needs multi-level memory caches when the clock cycle is pathetically slow?) and no need to worry about write endurance exhaustion with core memory, either. So how much of the consistency benefits are due to the hardware, and how much is due to the OS? We could just as easily claim that Multics is superior to Unix because it's immune to Spectre and Meltdown attacks --- except that Unix on a PDP-11 would be immune to cache based attacks as well. Of course, Unix on a PDP-11 is a lot slower than NetBSD on an modern x86_64 machines.... > Multics dynamic linking makes any unix-ish implementation look most > ugly, incredibly insecure, and horribly inefficient. Unix shared > libraries are bad hack to simulate what Multics did natively and > naturally, with elegance, and with direct hardware security support. What if we compared Multics dynamic linking to Solaris Doors? - Ted