How to disable Garbage Collection in GHC Haskell?

Question

How can I disable GCs, or vastly decrease the frequency of GCs?

Like giving it an +RTS option for some huge heap or or allocation size maybe?

I want to see how my program behaves when no GCs happen.

Answer 1

I had good results combining nh2 and Thomas's answers into

+RTS -I0 -A90G -G1 -m1 -RTS

I have 100 GB of RAM, so I thought 90G was a good allocation area size.

I also used System.Mem.performGC to manually trigger GC at appropriate points and GHC.Stats to keep track of how much time has been spent in GC.

Answer 2

(With the help from carter in #ghc on freenode)

There is no switch to completely disable GC. Instead, use all of the following +RTS runtime options:

• Disable idle time garbage collection using -I0.
• Set the "nursery" == "allocation area" size to something very large, e.g. -A100G, as GC will only be done when the allocation area is full.

See https://downloads.haskell.org/~ghc/7.8-latest/docs/html/users_guide/runtime-control.html for a description of these options.

Be aware that you will run out of RAM quickly.