At Sat, 8 Aug 2020 03:32:57 -0400, George Neuner wrote: > > On 8/8/2020 1:55 AM, Sorawee Porncharoenwase wrote: > > I even saw people doing `collect-garbage` three times, just to be safe > > I guess. And yet theoretically it's not guaranteed that things will be > > claimed back properly. > > > > Honestly, there should be a function that does this `collect-garbage` > > until fixpoint or something, so that we don't need to perform this ... > > uh .... ritual. > > There may be no documented guarantee, but I *think* the implementation > assures that 2 collections, back-to-back, are sufficient to reclaim all > objects that were garbage at the beginning of the 1st collection. At > least for BC Racket.
In the absence of finalization, then a single `collect-garbage` would always be sufficient, and a second `collect-garage` would have no effect. For the specific benchmark in this thread as run in plain `racket`, I think a single `collect-garbage` is sufficient, and that's what I normally do. But finalization complicates the picture --- especially finalization via `register-finalizer`, since the finalizers run in a background thread. Because of that background thread, in a context that uses a library like `racket/gui`, I sometimes use repetitions of (collect-garbage) (sync (system-idle-evt)) It's difficult to know whether the libraries that you use rely on finalization. Also, finalization means that there is no simple number of `(collect-garbage)`s and `(sync (system-idle-evt))`s that are needed to really collect everything that could potentially be collected; finalization chains can require an arbitrary number of `(collect-garbage)` cycles to clean up (so libraries should avoid finalization chains!). The collector is precise and the compiler is safe-for-space, so you can reason about the reachability of an individual value, but reasoning precisely about overall memory use across many libraries is difficult or impossible. Using an extra `(collect-garbage)` is not ideal and often not necessary, but it's a reasonable just-to-be-sure habit. Matthew -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/20200808074547.3a2%40sirmail.smtps.cs.utah.edu.
