Save-metas causes OOM during macro execution

[plt-amy]

Save-metas causes OOM during macro execution

[plt-amy]

To be clear I killed the save-metas run in this file because checking it successfully has max residency a bit over 1GiB:

  78,604,576,424 bytes allocated in the heap
   9,346,647,992 bytes copied during GC
   1,047,939,672 bytes maximum residency (57 sample(s))
       2,221,480 bytes maximum slop
            2223 MiB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0     18826 colls,     0 par    4.783s   4.790s     0.0003s    0.0018s
  Gen  1        57 colls,     0 par    4.125s   4.126s     0.0724s    1.1531s

  TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1)

  SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

  INIT    time    0.000s  (  0.000s elapsed)
  MUT     time   22.201s  ( 22.178s elapsed)
  GC      time    8.909s  (  8.916s elapsed)
  EXIT    time    0.000s  (  0.006s elapsed)
  Total   time   31.110s  ( 31.100s elapsed)

  Alloc rate    3,540,642,516 bytes per MUT second

  Productivity  71.4% of total user, 71.3% of total elapsed

[ncfavier]

#7231