nonmoving: Clear segment bitmaps during sweep

Previously we would clear the bitmaps of segments which we are going to
sweep during the preparatory pause. However, this is unnecessary: the
existence of the mark epoch ensures that the sweep will correctly
identify non-reachable objects, even if we do not clear the bitmap.

We now defer clearing the bitmap to sweep, which happens concurrently
with mutation.

1 files changed, 1 insertions, 0 deletions

diff --git a/rts/sm/NonMovingSweep.c b/rts/sm/NonMovingSweep.c
index b390959612..925d7c2068 100644
--- a/rts/sm/NonMovingSweep.c
+++ b/rts/sm/NonMovingSweep.c
@@ -65,6 +65,7 @@ nonmovingSweepSegment(struct NonmovingSegment *seg)
     } else {
         ASSERT(seg->next_free == 0);
         ASSERT(nonmovingSegmentInfo(seg)->next_free_snap == 0);
+        nonmovingClearBitmap(seg);
         return SEGMENT_FREE;
     }
 }