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diff --git a/web/l-plan9.html b/web/l-plan9.html deleted file mode 100644 index a3af3d5..0000000 --- a/web/l-plan9.html +++ /dev/null @@ -1,249 +0,0 @@ -<html> -<head> -<title>Plan 9</title> -</head> -<body> - -<h1>Plan 9</h1> - -<p>Required reading: Plan 9 from Bell Labs</p> - -<h2>Background</h2> - -<p>Had moved away from the ``one computing system'' model of -Multics and Unix.</p> - -<p>Many computers (`workstations'), self-maintained, not a coherent whole.</p> - -<p>Pike and Thompson had been batting around ideas about a system glued together -by a single protocol as early as 1984. -Various small experiments involving individual pieces (file server, OS, computer) -tried throughout 1980s.</p> - -<p>Ordered the hardware for the ``real thing'' in beginning of 1989, -built up WORM file server, kernel, throughout that year.</p> - -<p>Some time in early fall 1989, Pike and Thompson were -trying to figure out a way to fit the window system in. -On way home from dinner, both independently realized that -needed to be able to mount a user-space file descriptor, -not just a network address.</p> - -<p>Around Thanksgiving 1989, spent a few days rethinking the whole -thing, added bind, new mount, flush, and spent a weekend -making everything work again. The protocol at that point was -essentially identical to the 9P in the paper.</p> - -<p>In May 1990, tried to use system as self-hosting. -File server kept breaking, had to keep rewriting window system. -Dozen or so users by then, mostly using terminal windows to -connect to Unix.</p> - -<p>Paper written and submitted to UKUUG in July 1990.</p> - -<p>Because it was an entirely new system, could take the -time to fix problems as they arose, <i>in the right place</i>.</p> - - -<h2>Design Principles</h2> - -<p>Three design principles:</p> - -<p> -1. Everything is a file.<br> -2. There is a standard protocol for accessing files.<br> -3. Private, malleable name spaces (bind, mount). -</p> - -<h3>Everything is a file.</h3> - -<p>Everything is a file (more everything than Unix: networks, graphics).</p> - -<pre> -% ls -l /net -% lp /dev/screen -% cat /mnt/wsys/1/text -</pre> - -<h3>Standard protocol for accessing files</h3> - -<p>9P is the only protocol the kernel knows: other protocols -(NFS, disk file systems, etc.) are provided by user-level translators.</p> - -<p>Only one protocol, so easy to write filters and other -converters. <i>Iostats</i> puts itself between the kernel -and a command.</p> - -<pre> -% iostats -xvdfdf /bin/ls -</pre> - -<h3>Private, malleable name spaces</h3> - -<p>Each process has its own private name space that it -can customize at will. -(Full disclosure: can arrange groups of -processes to run in a shared name space. Otherwise how do -you implement <i>mount</i> and <i>bind</i>?)</p> - -<p><i>Iostats</i> remounts the root of the name space -with its own filter service.</p> - -<p>The window system mounts a file system that it serves -on <tt>/mnt/wsys</tt>.</p> - -<p>The network is actually a kernel device (no 9P involved) -but it still serves a file interface that other programs -use to access the network. -Easy to move out to user space (or replace) if necessary: -<i>import</i> network from another machine.</p> - -<h3>Implications</h3> - -<p>Everything is a file + can share files => can share everything.</p> - -<p>Per-process name spaces help move toward ``each process has its own -private machine.''</p> - -<p>One protocol: easy to build custom filters to add functionality -(e.g., reestablishing broken network connections). - -<h3>File representation for networks, graphics, etc.</h3> - -<p>Unix sockets are file descriptors, but you can't use the -usual file operations on them. Also far too much detail that -the user doesn't care about.</p> - -<p>In Plan 9: -<pre>dial("tcp!plan9.bell-labs.com!http"); -</pre> -(Protocol-independent!)</p> - -<p>Dial more or less does:<br> -write to /net/cs: tcp!plan9.bell-labs.com!http -read back: /net/tcp/clone 204.178.31.2!80 -write to /net/tcp/clone: connect 204.178.31.2!80 -read connection number: 4 -open /net/tcp/4/data -</p> - -<p>Details don't really matter. Two important points: -protocol-independent, and ordinary file operations -(open, read, write).</p> - -<p>Networks can be shared just like any other files.</p> - -<p>Similar story for graphics, other resources.</p> - -<h2>Conventions</h2> - -<p>Per-process name spaces mean that even full path names are ambiguous -(<tt>/bin/cat</tt> means different things on different machines, -or even for different users).</p> - -<p><i>Convention</i> binds everything together. -On a 386, <tt>bind /386/bin /bin</tt>. - -<p>In Plan 9, always know where the resource <i>should</i> be -(e.g., <tt>/net</tt>, <tt>/dev</tt>, <tt>/proc</tt>, etc.), -but not which one is there.</p> - -<p>Can break conventions: on a 386, <tt>bind /alpha/bin /bin</tt>, just won't -have usable binaries in <tt>/bin</tt> anymore.</p> - -<p>Object-oriented in the sense of having objects (files) that all -present the same interface and can be substituted for one another -to arrange the system in different ways.</p> - -<p>Very little ``type-checking'': <tt>bind /net /proc; ps</tt>. -Great benefit (generality) but must be careful (no safety nets).</p> - - -<h2>Other Contributions</h2> - -<h3>Portability</h3> - -<p>Plan 9 still is the most portable operating system. -Not much machine-dependent code, no fancy features -tied to one machine's MMU, multiprocessor from the start (1989).</p> - -<p>Many other systems are still struggling with converting to SMPs.</p> - -<p>Has run on MIPS, Motorola 68000, Nextstation, Sparc, x86, PowerPC, Alpha, others.</p> - -<p>All the world is not an x86.</p> - -<h3>Alef</h3> - -<p>New programming language: convenient, but difficult to maintain. -Retired when author (Winterbottom) stopped working on Plan 9.</p> - -<p>Good ideas transferred to C library plus conventions.</p> - -<p>All the world is not C.</p> - -<h3>UTF-8</h3> - -<p>Thompson invented UTF-8. Pike and Thompson -converted Plan 9 to use it over the first weekend of September 1992, -in time for X/Open to choose it as the Unicode standard byte format -at a meeting the next week.</p> - -<p>UTF-8 is now the standard character encoding for Unicode on -all systems and interoperating between systems.</p> - -<h3>Simple, easy to modify base for experiments</h3> - -<p>Whole system source code is available, simple, easy to -understand and change. -There's a reason it only took a couple days to convert to UTF-8.</p> - -<pre> - 49343 file server kernel - - 181611 main kernel - 78521 ipaq port (small kernel) - 20027 TCP/IP stack - 15365 ipaq-specific code - 43129 portable code - -1326778 total lines of source code -</pre> - -<h3>Dump file system</h3> - -<p>Snapshot idea might well have been ``in the air'' at the time. -(<tt>OldFiles</tt> in AFS appears to be independently derived, -use of WORM media was common research topic.)</p> - -<h3>Generalized Fork</h3> - -<p>Picked up by other systems: FreeBSD, Linux.</p> - -<h3>Authentication</h3> - -<p>No global super-user. -Newer, more Plan 9-like authentication described in later paper.</p> - -<h3>New Compilers</h3> - -<p>Much faster than gcc, simpler.</p> - -<p>8s to build acme for Linux using gcc; 1s to build acme for Plan 9 using 8c (but running on Linux)</p> - -<h3>IL Protocol</h3> - -<p>Now retired. -For better or worse, TCP has all the installed base. -IL didn't work very well on asymmetric or high-latency links -(e.g., cable modems).</p> - -<h2>Idea propagation</h2> - -<p>Many ideas have propagated out to varying degrees.</p> - -<p>Linux even has bind and user-level file servers now (FUSE), -but still not per-process name spaces.</p> - - -</body> |