MPS issue job001092

Title	MPS is not integrated with public cool projects.
Status	open
Priority	optional
Assigned user	Gareth Rees
Organization	Ravenbrook
Description	Although the MPS works well in some commercial and open source settings, it isn't very visible in popular projects. The MPS needs to be deployed as a memory manager and integrated into some cool projects. This is to: - Raise awareness of the MPS. - Make the MPS flexible (can be used in many different scenarios). - Prove that that MPS is flexible. So that: - The industry is improved by knowing about and using the MPS - Ravenbrook can attract MPS licensees.
Analysis	Some cool projects into which the MPS could possibly be integrated: Java, Parrot, Lua, perl, Python, Kaffe, SIOD, Objective-C, C--, PTL Scheme (see [10]). Recently (to 2007-02-20) we have also been investigating SC (rb's pet scheme compiler) and CMUCL. Cost factors: - availability of source code. - documentation for source code. - niceness of source code. - suitability of project for slottable memory manager. Coolness: Java would be maximally cool, source code is generally available, try http://www.sun.com/software/communitysource/j2se/java2/download.xml We wouldn't be able to distribute this source, but we would be able to use it for an internal integration. (The source used to be not so readily available, but times have changed). Parrot is cool. Lua is cool but obscure. Is gaining ground in the games industry (which is a cool sector). perl and Python are cool. Kaffe is cool but not making much noise these days. SIOD is only cool to schemers and lispers. Sorry. Objective C is in Mac OS X so is cool by association. C-- is a bit unkown to DRJ. SIOD: Is it still used? Not much sign of life since 1996. Sounds like (from reading [7]) that integration would be fairly easy. The existing stop-and-copy GC is about 40 lines long. Advantage of MPS: incremental. Possible advantages are that we could get an integration done in a very small time and that would give us valuable experience in doing integrations and would help RichardK. Also any experience in doing any integration would, if documented, go towards the creation of the Integrator's Manual. Lua: Lua 5.1 has an incremental GC. This version of Lua is now generally available. DRJ's expertise in Lua is mostly with 4.x. Will need to look at 5.x source code to see how much has changed. Lua 5 has weak tables. Weak key, weak value, or weak both. User selectable in a slightly horrid way (see http://www.lua.org/manual/5.0/manual.html#2.9.2 ), but it does make sense from the Lua programmer's perspective. I think this might be an issue in the integration. Naively it seems that the weakness (rank) of table T depends on an object (a string) referenced from T's metatable M. However, the restrictions on the metatable mean that a table's weakness is set from one invocation of setmetatable to the next. This is still a bit boggling. GDR had a go (starting with no knowledge of the MPS) at replacing Lua's own mark-and-sweep GC with the MPS in 2012-09 and got more or less everything working except finalization and weak hash tables [13] [14] [15] [16] [17] [18] [19] [20] [21] [22]. Performance was not so good. The weak hash tables would be a problem. Code leftover from this work is in //info.ravenbrook.com/user/gdr/project/luamps/... Parrot: You ought to know that PMC stands for Parrot Magic Cookie. I think this is an allocated object with an abstracted interface, but it's a bit hard to tell. http://www.parrotcode.org/docs/pdd/pdd02_vtables.html reveals a mark vtable method. This seems to be like our object scan method. Except that there is no callback to call. src/malloc.c is a copy of Doug Lea malloc. Or started out that way. (red herring). This Parrot Design Document seems useful: http://www.parrotcode.org/docs/pdd/pdd09_gc.html Objective-C: As seen in Mac OS X. These days I think everyone thinks of Mac OS X when they think of Objective-C. See [8]. Cocoa uses reference counting, see [8]/The Runtime System/Memory Management. Reference counting is manual, that is the Cocoa programmer must write explicit method calls to manage the reference count. The methods are "retain", "release", and "autorelease". I find the exact semantics difficult to pin down. See http://www.macdevcenter.com/lpt/a/2418 Runtime source: http://cvs.opendarwin.org/index.cgi/src/objc4/runtime/ RB says: ObjC new object calls _alloc calls _internal_class_createInstanceFromZone calls malloc! Java: See Goran's war story [9] LLVM Built-in support for interfacing with garbage collectors. See [24]. Mono Mono ships with two garbage collectors (a generational collector, and Boehm-Weiser conservative collector) which is not a very promising sign. See Wikipedia for some analysis. [23] 2007-04-12 DRJ: See some general integration notes (what to think about when integrating): [12]
How found	unknown
Evidence	[1] http://www.parrotcode.org/ [2] http://www.lua.org/ [3] http://www.perl.com/ [4] http://www.python.org/ [5] http://www.kaffe.org/ [6] http://wwws.sun.com/software/java/ [7] http://www.cs.indiana.edu/scheme-repository/imp/siod.html [8] http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/ [9] //info.ravenbrook.com/mail/2004/09/06/09-11-16/0.txt [10] //info.ravenbrook.com/mail/2004/12/17/00-34-42/0.txt [11] http://www.plt-scheme.org/ [12] //info.ravenbrook.com/mail/2007/03/30/14-07-30/0.txt [13] <https://info.ravenbrook.com/mail/2012/09/19/16-54-01/0/> [14] <http://info.ravenbrook.com/mail/2012/09/20/16-06-48/0/> [15] <http://info.ravenbrook.com/mail/2012/09/21/14-58-15/0/> [16] <https://info.ravenbrook.com/mail/2012/09/27/18-07-06/0/> [17] <https://info.ravenbrook.com/mail/2012/09/28/17-12-07/0/> [18] <https://info.ravenbrook.com/mail/2012/10/03/08-29-14/0/> [19] <https://info.ravenbrook.com/mail/2012/10/03/16-35-24/0/> [20] <https://info.ravenbrook.com/mail/2012/10/04/17-38-59/0/> [21] <https://info.ravenbrook.com/mail/2012/10/07/22-17-57/0/> [22] <https://info.ravenbrook.com/mail/2012/10/08/18-55-13/0/> [23] <http://en.wikipedia.org/wiki/Mono_(software)#Garbage_collector> [24] <http://llvm.org/docs/GarbageCollection.html>
Observed in	1.100.0
Created by	David Jones
Created on	2004-12-10 15:58:38
Last modified by	Gareth Rees
Last modified on	2016-09-13 10:37:40
History	2004-12-10 DRJ Created and some analysis. 2006-04-19 DRJ Now available: Lua 5.1, Java source. 2007-02-20 DRJ Note about SC and CMUCL 2007-04-12 DRJ Notes about integration notes 2012-10-25 GDR Added notes about Lua/MPS integration; LLVM; Mono. 2013-03-19 GDR Assigned to GDR.