gc suggestions

[Dirk Herrmann <dirk at ida dot ing dot tu-bs dot de>]

Hello list.

I have the following suggestions for changes to the gc:

Problem:
  The variable scm_gc_heap_lock blocks, if non-zero, the creation of new
  heap segments, except for the very first heap segment, which is created
  independently.  This variable is initialized to zero, which means, that
  even during the startup phase of guile new heap segments could be
  potentially added, for example if the initial heap segment appears to be
  too small.

  The disadvantage of this behaviour is, that all initializations, which
  are needed before the first gc is performed, have to be done very early
  in scm_init_storage.  This leads to the situation that some
  initializations which would better fit into async.c are performed in
  gc.c, since the implementation of the gc relies on asyncs being
  initialized.

Thus:
  I suggest to initialize scm_gc_heap_lock with 1 until scm_init_gc is
  performed.  Then, we just have to make sure that all initialization code
  that scm_init_gc depends on is performed before in init.c.  Thus, we
  achieve the following goals:
  - the initialization of the asyncs is performed at the right place.
  - if the initial heap segment appears to be too small to be suffifient
    until scm_init_gc is performed, guile aborts and can be fixed in order
    to enlarge the initial heap segment.

i. e.:

  * If set, don't expand the heap.  Set only during gc, during which no allocation
  * is supposed to take place anyway.
  */
-int scm_gc_heap_lock = 0;
+int scm_gc_heap_lock = 1;
 
 /* GC Blocking
  * Don't pause for collection if this is set -- just



(the comment should be updated also) and


 scm_init_gc ()
 {
   scm_after_gc_hook = scm_create_hook ("after-gc-hook", 0);
+  scm_gc_heap_lock = 0;
 #include "libguile/gc.x"
 }
 

Best regards
Dirk