On 01/10/2015 07:53 PM, Gabor Szabo wrote:
> On Sat, Jan 10, 2015 at 7:57 PM, <t...@wakelift.de
> <mailto:t...@wakelift.de>> wrote:
>
> That happens because the result of the for statement is a list that is
> then sunk; it contains one scalar and one Int object for each
> iteration
> and rakudo doesn't yet know to throw it away immediately.
>
>
> The problem happens even without the internal $x variable, but my main
> problem
> is that this means the web application running the Perl6Maven.com site
> fills the memory
> after just a few requests.
>
> A quick check seems to indicated that while-loops don't have the same
> memory leak,
> but before I run and rewrite every for loop into a while-loop, it
> would be nice to know
> if there are other parts of the language that are leaking memory?
>
>
> regards
> Gabor
>
Fortunately, it's not as bad as you think. Compare these two invocations:
time perl6 -e 'for ^1000 { for ^1000 { }; 1 }'
0.91user 0.02system 0:00.94elapsed 99%CPU (0avgtext+0avgdata
113448maxresident)k
time perl6 -e 'for ^1000 { for ^10000 { }; 1 }'
5.53user 0.02system 0:05.59elapsed 99%CPU (0avgtext+0avgdata
114744maxresident)k
The MaxRSS hardly differs, because the list that belongs to the inner
for loop gets garbage collected properly.
There isn't an actual memory leak, it's just that the result of the for
loop is (wrongly) being kept around.
There was also an optimization that turns a for ^1000 loop into a while
loop with a native counter for great performance improvements, but that
got b0rked at some point ;(
regards
- Timo
