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Date: Sun, 2 Jan 2005 12:04:33 +1300
From: Jonathan Roewen <jonathan.roewen@gmail.com>
Reply-To: Jonathan Roewen <jonathan.roewen@gmail.com>
To: caml-list@yquem.inria.fr
Subject: [Caml-list] Garbage Collecting
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Hi,

We're trying to figure out why memory doesn't get collected in our OS
by the OCaml GC, and seems like it doesn't want to reclaim any memory.
We also suspect that Gc.allocated_bytes has a memory leak.

Here is our test case:
(* File mod.ml -- some ``useful'' Caml functions *)
open Printf

let fib (n:int) =1 + n

;;

let mem = ref 0;;
let do_stuff () = 
(* 	making this loop more increases mem usage *)
	for i=1 to 900000 do
		fib i;
		int_of_float (Gc.allocated_bytes()); (* A *)
	done;
	mem := int_of_float (Gc.allocated_bytes())
;;

let do_results() = 
	printf "allocated %d\n" !mem;
	Gc.full_major(); (* B1 *)
	Gc.compact();
	Gc.major();
	Gc.minor(); (*B2 *)
	printf "allocated %d\n" (int_of_float (Gc.allocated_bytes()))
;;
do_stuff ();;
do_results ();;

My results:
Test 1)
allocated 57600272
allocated 57600788
Test 2)
allocated 272
allocated 956
Test 3)
allocated 272
allocated 744

Where test 1 is using the above code; test 2 is with line A commented
out; and test 3 is with both line A and lines B1-B2 commented out.

As you can see from our tests, that invoking the Gc increases memory,
and Gc.allocated_bytes appears to gobble it up like candy.

Would appreciate someone shedding some light on this topic, as writing
our OS in OCaml is going to have some major issues if it won't reclaim
memory.

Regards,

Jonathan