Unconditionally flush update remembered set during minor GCwip/gc/optimize

Flush the update remembered set. The goal here is to flush periodically to
ensure that we don't end up with a thread who marks their stack on their
local update remembered set and doesn't flush until the nonmoving sync
period as this would result in a large fraction of the heap being marked
during the sync pause.

1 files changed, 8 insertions, 0 deletions

diff --git a/rts/sm/GC.c b/rts/sm/GC.c
index 6be81e5ff0..83e9c97bd9 100644
--- a/rts/sm/GC.c
+++ b/rts/sm/GC.c
@@ -730,6 +730,14 @@ GarbageCollect (uint32_t collect_gen,
     }
   } // for all generations
 
+  // Flush the update remembered set. See Note [Eager update remembered set
+  // flushing] in NonMovingMark.c
+  if (RtsFlags.GcFlags.useNonmoving) {
+      RELEASE_SM_LOCK;
+      nonmovingAddUpdRemSetBlocks(&gct->cap->upd_rem_set.queue);
+      ACQUIRE_SM_LOCK;
+  }
+
   // Mark and sweep the oldest generation.
   // N.B. This can only happen after we've moved
   // oldest_gen->scavenged_large_objects back to oldest_gen->large_objects.