=================================================================== RCS file: /home/cvs/OpenXM_contrib/gc/Attic/README,v retrieving revision 1.1.1.1 retrieving revision 1.1.1.2 diff -u -p -r1.1.1.1 -r1.1.1.2 --- OpenXM_contrib/gc/Attic/README 1999/11/27 10:58:32 1.1.1.1 +++ OpenXM_contrib/gc/Attic/README 2000/04/14 11:08:01 1.1.1.2 @@ -1,6 +1,7 @@ Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers Copyright (c) 1991-1996 by Xerox Corporation. All rights reserved. -Copyright (c) 1996-1998 by Silicon Graphics. All rights reserved. +Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved. +Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved. THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK. @@ -11,19 +12,19 @@ Permission to modify the code and to distribute modifi provided the above notices are retained, and a notice that the code was modified is included with the above copyright notice. -This is version 4.14 of a conservative garbage collector for C and C++. +This is version 5.0alpha4 of a conservative garbage collector for C and C++. You might find a more recent version of this at -http://reality.sgi.com/boehm/gc.html +http://www.hpl.hp.com/personal/Hans_Boehm/gc HISTORY - Early versions of this collector were developed as a part of research projects supported in part by the National Science Foundation and the Defense Advance Research Projects Agency. -Much of the code was rewritten by Hans-J. Boehm at Xerox PARC -and is now maintained by him at SGI (boehm@sgi.com). +Much of the code was rewritten by Hans-J. Boehm (boehm@acm.org) at Xerox PARC +and at SGI. Some other contributors: @@ -40,8 +41,8 @@ Robert Brazile (brazile@diamond.bbn.com) originally su Al Dosser (dosser@src.dec.com) and Regis Cridlig (Regis.Cridlig@cl.cam.ac.uk) subsequently provided updates and information on variation between ULTRIX systems. Parag Patel (parag@netcom.com) supplied the A/UX code. -Jesper Peterson(jep@mtiame.mtia.oz.au) and -Michel Schinz supplied the Amiga port. +Jesper Peterson(jep@mtiame.mtia.oz.au), Michel Schinz, and +Martin Tauchmann (martintauchmann@bigfoot.com) supplied the Amiga port. Thomas Funke (thf@zelator.in-berlin.de(?)) and Brian D.Carlstrom (bdc@clark.lcs.mit.edu) supplied the NeXT ports. Douglas Steel (doug@wg.icl.co.uk) provided ICL DRS6000 code. @@ -612,7 +613,7 @@ reclaimed. Exclusive-or'ing forward and backward link doesn't cut it. Some C optimizers may lose the last undisguised pointer to a memory object as a consequence of clever optimizations. This has almost -never been observed in practice. Send mail to boehm@sgi.com +never been observed in practice. Send mail to boehm@acm.org for suggestions on how to fix your compiler. This is not a real-time collector. In the standard configuration, percentage of time required for collection should be constant across @@ -621,7 +622,7 @@ heap sizes. But collection pauses will increase for l per MB of accessible memory that needs to be scanned. Your mileage may vary.) The incremental/generational collection facility helps, but is portable only if "stubborn" allocation is used. - Please address bug reports to boehm@sgi.com. If you are + Please address bug reports to boehm@acm.org. If you are contemplating a major addition, you might also send mail to ask whether it's already been done (or whether we tried and discarded it). @@ -1451,7 +1452,78 @@ Since 4.14alpha1 Since 4.14alpha2 - changed STACKBOTTOM for DJGPP (Thanks to Salvador Eduardo Tropea). + +Since 4.14 + - Reworked large block allocator. Now uses multiple doubly linked free + lists to approximate best fit. + - Changed heap expansion heuristic. Entirely free blocks are no longer + counted towards the heap size. This seems to have a major impact on + heap size stability; the old version could expand the heap way too + much in the presence of large block fragmentation. + - added -DGC_ASSERTIONS and some simple assertions inside the collector. + This is mainlyt for collector debugging. + - added -DUSE_MUNMAP to allow the heap to shrink. Suupported on only + a few UNIX-like platforms for now. + - added GC_dump_regions() for debugging of fragmentation issues. + - Changed PowerPC pointer alignment under Linux to 4. (This needs + checking by someone who has one. The suggestions came to me via a + rather circuitous path.) + - Changed the Linux/Alpha port to walk the data segment backwards until + it encounters a SIGSEGV. The old way to find the start of the data + segment broke with a recent release. + - cordxtra.c needed to call GC_REGISTER_FINALIZER instead of + GC_register_finalizer, so that it would continue to work with GC_DEBUG. + - allochblk sometimes cleared the wrong block for debugging purposes + when it dropped blacklisted blocks. This could result in spurious + error reports with GC_DEBUG. + - added MACOS X Server support. (Thanks to Andrew Stone.) + - Changed the Solaris threads code to ignore stack limits > 8 MB with + a warning. Empirically, it is not safe to access arbitrary pages + in such large stacks. And the dirty bit implementation does not + guarantee that none of them will be accessed. + - Integrated Martin Tauchmann's Amiga changes. + - Integrated James Dominy's OpenBSD/SPARC port. +Since 5.0alpha1 + - Fixed bugs introduced in alpha1 (OpenBSD & large block initialization). + - Added -DKEEP_BACK_PTRS and backptr.h interface. (The implementation + idea came from Al Demers.) + +Since 5.0alpha2 + - Added some highly incomplete code to support a copied young generation. + Comments on nursery.h are appreciated. + - Changed -DFIND_LEAK, -DJAVA_FINALIZATION, and -DFINALIZE_ON_DEMAND, + so the same effect could be obtained with a runtime switch. This is + a step towards standardizing on a single dynamic GC library. + - Significantly changed the way leak detection is handled, as a consequence + of the above. + +Since 5.0 alpha3 + - Added protection fault handling patch for Linux/M68K from Fergus + Henderson and Roman Hodek. + - Removed the tests for SGI_SOURCE in new_gc_alloc.h. This was causing that + interface to fail on nonSGI platforms. + - Changed the Linux stack finding code to use /proc, after chnging it + to use HEURISTIC1. (Thanks to David Mossberger for pointing out the + /proc hook.) + - Added HP/UX incremental GC support and HP/UX 11 thread support. + - Added basic Linux/IA64 support. + - Integrated Anthony Green's PicoJava support. + - Integrated Scott Ananian's StrongARM/NetBSD support. + - Fixed some fairly serious performance bugs in the incremental + collector. These have probably been there essentially forever. + (Mark bits were sometimes set before scanning dirty pages. + The reclaim phase unnecessarily dirtied full small object pages.) + - Changed the reclaim phase to ignore nearly full pages to avoid + touching them. + - Limited GC_black_list_spacing to roughly the heap growth increment. + - Changed full collection triggering heuristic to decrease full GC + frequency by default, but to explicitly trigger full GCs during + heap growth. This doesn't always improve things, but on average it's + probably a win. + - GC_debug_free(0, ...) failed. Thanks to Fergus Henderson for the + bug report and fix. + To do: - Very large root set sizes (> 16 MB or so) could cause the collector to abort with an unexpected mark stack overflow. (Thanks again to @@ -1465,13 +1537,6 @@ To do: be possible to conditionally intercept mmap and use GC_exclude_static_roots. The real fix is to walk rld data structures, which looks possible. - Integrate MIT and DEC pthreads ports. - - Deal with very uneven black-listing distributions. If all the black listed - blocks reside in the newly allocated heap section, the heuristic for - temporarily ignoring black-listing fails, and the heap grows too much. - (This was observed in only one case, and could be worked around, but ...) - - I've started work on rewriting the large block allocator to use approximate - best fit. There are rare cases in which the current allocator results in - excessive large block fragmentation, even with the 4.13 fixes. This should - also reduce large block allocation time, whcih has become occasionally - noticable in 4.13. - + - Incremental collector should handle large objects better. Currently, + it looks like the whole object is treated as dirty if any part of it + is.