[racket] Periodic calls to collect-garbage?

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Thu Jul 14 15:23:33 EDT 2011

This sounds like a bug. Explicit calls to `collect-garbage' shouldn't
be needed for the garage collector to do its job.

Does anyone know an easy way for me to make the problem happen, so I
can see what is going on?

At Thu, 14 Jul 2011 12:47:54 -0400, Greg Hendershott wrote:
> Once upon a time I noticed the Racket web server has a thread that
> calls collect-garbage periodically (e.g. every 5 minutes).
> I've discovered I need to do the same, for any program that needs to
> run for hours or days.  Otherwise, the program eventually abends: Out
> of memory. Sometimes with a "Racket virtual machine error" message.
> This is my experience on both Windows 7 and on Linux, with Racket 5.0
> and 5.1.1.
> As a result the following has become a "magic spell" I now throw into
> such programs:
> ;; Make a thread to do garbage collection every 5 minutes.
> (thread
>  (lambda ()
>    (let loop ()
>      (sleep (* 5 60))
>      (collect-garbage)
>      (loop))))
> It seems weird to have such a magic spell, and to know it only from
> nosing around the web server source.
> Instead, maybe the Racket runtime should do this automatically (at
> least by default)? I think that's people would expect coming from some
> other language environments with GC (at least it's what I expected).
> Or, at least it would be documented that this is by-design (say for
> performance reasons, or there's no reasonable default, or whatever),
> and that people should use such a magic spell for long-running
> systems?
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