Commit 990171bf authored by Simon Marlow's avatar Simon Marlow
Browse files

tweak the totally-bogus arbitrary stack-squeezing heuristic to fix #2797

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.
parent a8a47739
......@@ -315,7 +315,8 @@ end:
// 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
......
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