diff options
| -rw-r--r-- | includes/rts/storage/ClosureMacros.h | 36 |
1 files changed, 26 insertions, 10 deletions
diff --git a/includes/rts/storage/ClosureMacros.h b/includes/rts/storage/ClosureMacros.h index 4d93994e4d..c4634f1c1e 100644 --- a/includes/rts/storage/ClosureMacros.h +++ b/includes/rts/storage/ClosureMacros.h @@ -457,20 +457,31 @@ INLINE_HEADER StgWord8 *mutArrPtrsCard (StgMutArrPtrs *a, W_ n) OVERWRITING_CLOSURE(p) on the old closure that is about to be overwritten. - In PROFILING mode, LDV profiling requires that we fill the slop - with zeroes, and record the old closure as dead (LDV_recordDead()). + Note [zeroing slop] - In DEBUG mode, we must overwrite the slop with zeroes, because the - sanity checker wants to walk through the heap checking all the - pointers. + In some scenarios we write zero words into "slop"; memory that is + left unoccupied after we overwrite a closure in the heap with a + smaller closure. - In multicore mode, we *cannot* overwrite slop with zeroes, because - another thread might be reading it. So, + Zeroing slop is required for: - LDV PROFILING is not compatible with +RTS -N<n> (for n > 1) + - full-heap sanity checks (DEBUG, and +RTS -DS) + - LDV profiling (PROFILING, and +RTS -hb) - THREADED_RTS can be used with DEBUG, but full heap sanity - checking is disabled except after major GC. + Zeroing slop must be disabled for: + + - THREADED_RTS with +RTS -N2 and greater, because we cannot + overwrite slop when another thread might be reading it. + + Hence, slop is zeroed when either: + + - PROFILING && era <= 0 (LDV is on) + - !THREADED_RTS && DEBUG + + And additionally: + + - LDV profiling and +RTS -N2 are incompatible + - full-heap sanity checks are disabled for THREADED_RTS -------------------------------------------------------------------------- */ @@ -489,6 +500,11 @@ EXTERN_INLINE void overwritingClosure (StgClosure *p) { nat size, i; +#if defined(PROFILING) && !defined(DEBUG) + // see Note [zeroing slop] + if (era <= 0) return; +#endif + size = closure_sizeW(p); // For LDV profiling, we need to record the closure as dead |