Re: What is best way to limit memory alloc?

[ludovic.courtes@laas.fr (Ludovic Courtès)]

Roland Orre <roland.orre@neurologic.se> writes:

> I found out that I had already solved the memory allocation
> problem in one way a few years ago.
> With the help of a small routine gc-heap-size, which accesses 
> scm_i_master_freelist.heap_size
> scm_i_master_freelist2.heap_size
> I did:
> (define gc-heap1 (gc-heap-size 1))
> (define gc-heap2 (gc-heap-size 2))
> (let loop
>    ....
>    (gc-heap-size 1 gc-heap1)
>    (gc-heap-size 2 gc-heap2)
>     (loop ...))
> By not allowing the heap size to increase.

That seems brutal. ;-)  What does `gc-heap-size' do exactly?

Another way would have been to fiddle with the `GUILE_MIN_YIELD_1' and
`GUILE_MIN_YIELD_2' environment variables.  These variables tell the GC
when it should grow the heap for the first and second freelist,
respectively.  More precisely, the GC does:

  if (number-of-cells-collected-recently < GUILE_MIN_YIELD_X)
  then
    allocate-new-heap
  else
    run-a-collection

(This takes place in `scm_i_gc_grow_heap_p ()' and `scm_gc_for_newcell ()'.)

The default value for `GUILE_MIN_YIELD_{1,2}' is 40, which means that if
the last GC run did not yield more than 40 cells, then more heap is
allocated.

If you set it to some _higher_ value, then the GC should be more
conservative and less memory-hungry, at the cost of being slower.

Thanks,
Ludovic.


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