I’m using 8.10.7 but this is a rare issue. The -O parameter vastly decreases the number of major GC performed and thus the probability to trigger the current instabilities in the RTS with -xn
In fact this -O parameter is a gem! I’ve looked for such a parameter but somehow missed it. With this and -F you can actually enforce a maximum soft limit on the memory usage without the caveats of the -M flag (which enables the compaction GC at a certain threshold severely degrading the performances).
To follow up on my previous post: -O does not prevent -Iw from triggering a major GC even well below the threshold set by -O.
I’m doing some tests concerning memory usage right now, I will report in this other thread to keep things separate.