In #2797, a program that ran in constant stack space when compiled
needed linear stack space when interpreted. It turned out to be
nothing more than stack-squeezing not happening. We have a heuristic
to avoid stack-squeezing when it would be too expensive (shuffling a
large amount of memory to save a few words), but in some cases even
expensive stack-squeezing is necessary to avoid linear stack usage.
One day we should implement stack chunks, which would make this less
expensive.
// the number of words we have to shift down is less than the
// number of stack words we squeeze away by doing so.
if (RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue &&
- ((weight <= 5 && words_to_squeeze > 0) || weight < words_to_squeeze)) {
+ ((weight <= 8 && words_to_squeeze > 0) || weight < words_to_squeeze)) {
+ // threshold above bumped from 5 to 8 as a result of #2797
stackSqueeze(cap, tso, (StgPtr)frame);
tso->flags |= TSO_SQUEEZED;
// This flag tells threadStackOverflow() that the stack was