clearing GHCi (and, by extension, hint) loaded module dependencies

Simon Marlow marlowsd at
Tue Oct 5 09:25:53 EDT 2010

On 26/09/2010 18:14, Alex Suraci wrote:
> On Sep 23, 2010, at 7:11 AM, Simon Marlow wrote:
>> If you are making separate runGhc calls and still don't see the
>> memory being reclaimed, then there might be a leak - but it's hard
>> to see where, since everything is reachable from the Session only.
>> I suppose we have some global linker state which might be holding
>> onto stuff, but as you say that loads are faster in subsequent
>> runs, that implies that you're using the same Session.
> Hm, I'm not doing any explicit Session handling/reusing. A new hint
> interpreter is run with every "load", and nothing is saved or
> continued between "load"s; by the time the interpreted function is
> executed, the interpreter has completed and its session is no longer
> needed. If the Session is sticking around anywhere, I'm not sure
> where it would be.
> Slightly verbose experimentation results:
> As an experiment I just tried adding hint's InterpreterT onto my
> language's VM stack, so that it's always running one continuous
> interpreter, and calling "reset" after interpreting the "load"
> function. An empty script bumped the usage by ~70MB, and subsequent
> loads of the same script had no discernible increase and completed
> instantly. (It seems the "reset" hint function has no effect on
> this.)
> Loading another script after the empty one (one that actually does
> something - an interface for the Snap webserver) only bumped up the
> RAM usage modestly (30MB), implying that some of its dependencies
> were already loaded. Doing the reverse (snap script ->  empty script)
> jumped the RAM usage up by ~100MB initially, and loading the empty
> script repeatedly had no increase and completed instantly.
> Repeating these tests with separate runInterpreter calls (how it was
> before) has the same characteristics, except that repeated loads of
> already-loaded scripts bump up the RAM usage slightly (~8-10MB for
> empty, ~20-40MB for snap).

How are you measuring the memory usage, btw?


More information about the Glasgow-haskell-users mailing list