new command-line option -nextgc-factor

[Bruno H. <br...@cl...>]

Hi all,

For debugging GC problems, I have added a new option -nextgc-factor.
It is a factor that gets applied to the amount of space that can be
consumed before the next GC is triggered.

Setting it to large values can inhibit GC for a long time:

$ ./lisp.run -q -M lispinit.mem -nextgc-factor 1e9
[1]> (time (setq a (make-array 1000000) b nil))
Real time: 0.038371 sec.
Run time: 0.04 sec.
Space: 8000016 Bytes
NIL
[2]> (room)

Number of garbage collections:                0
Bytes freed by GC:                            0
Time spent in GC:                           0.0 sec
Bytes permanently allocated:            158,480
Bytes currently in use:              11,107,792
Bytes available until next GC: 1,536,935,991,966,080
11107792 ;
1536935991966080 ;
158480 ;
0 ;
0 ;
0

Setting it to small values can make GCs much more frequent:

$ ./lisp.run -q -M lispinit.mem -nextgc-factor 0.001
[1]> (room)

Number of garbage collections:               16
Bytes freed by GC:                       44,648
Time spent in GC:                         1.112 sec
Bytes permanently allocated:            158,480
Bytes currently in use:               3,056,200
Bytes available until next GC:               71
3056200 ;
71 ;
158480 ;
16 ;
44648 ;
1112000
[2]> (time (setq a (make-list 1000) b nil))
Real time: 0.687479 sec.
Run time: 0.688 sec.
Space: 16000 Bytes
GC: 10, GC time: 0.688 sec.
NIL


I don't want to document this option, because the default GC frequency
is completely sufficient for the average user.

Bruno