From hughrsimpson@gmail.com

`perl6 -e 'my ($x,$y,$i) = (0,1,1); while ($i < 1000000) {$y += $x ; $x =
$y - $x ; $i += 1 } ; say $y;'` eats up 6GB of RAM on my system

$ perl6 -v
This is perl6 version 2015.09-433-g26617f9 built on MoarVM version
2015.09-79-gee9fc2b

From @MasterDuke17

The reason behind this behavior is that a bigint takes only very little space in the nursery, but it can hold on to a gigantic buffer. This was fixed by reducing the nursery limit by the size of the bigint buffer when they are created, triggering garbage collection earlier.

`/usr/bin/time ./install/bin/perl6-m -e 'my ($x,$y,$i) = (0,1,1); while ($i < 1000000) {$y += $x ; $x = $y - $x ; $i += 1 } ; say $y;'` now reports 124MB instead of 6GB.

Fixed in MoarVM commit MoarVM/MoarVM@63430ac
Brought into Rakudo in commit rakudo/rakudo@a123eb3

@MasterDuke17 - Status changed from 'new' to 'resolved'