idle GC causes large CPU usage if run more frequently than 1 second
I have a web server which exhibits unusual CPU usage. When it first starts it loads a bunch of state from disk -- around 800MB. It then sits idle consuming no CPU. If I make any request to the server, it starts using 30-60% of the CPU and never goes back down -- even if the request does not interact with the state system at all.
If I disable idle GC, then the problem goes away. If I set idle GC time using,
+RTS -I1, the problem goes away. If I set it to,
+RTS -I0.9999999, then I see the CPU usage issue.
+RTS -I1 option is sufficient for now, but the documentation says I should report any weirdness.
I do not have a simple test case for this.