Return memory to the OS; trac #698

[ghc-hetmet.git] / rts / sm / GC.c

diff --git a/rts/sm/GC.c b/rts/sm/GC.c
index 34aa0fd..191310a 100644 (file)
--- a/rts/sm/GC.c
+++ b/rts/sm/GC.c
@@ -727,11 +727,6 @@ SET_GCT(gc_threads[0]);
   // Reset the nursery
   resetNurseries();
 
-  // start any pending finalizers 
-  RELEASE_SM_LOCK;
-  scheduleFinalizers(cap, old_weak_ptr_list);
-  ACQUIRE_SM_LOCK;
-  
   // send exceptions to any threads which were about to die 
   RELEASE_SM_LOCK;
   resurrectThreads(resurrected_threads);
@@ -740,6 +735,30 @@ SET_GCT(gc_threads[0]);
   // Update the stable pointer hash table.
   updateStablePtrTable(major_gc);
 
+  // unlock the StablePtr table.  Must be before scheduleFinalizers(),
+  // because a finalizer may call hs_free_fun_ptr() or
+  // hs_free_stable_ptr(), both of which access the StablePtr table.
+  stablePtrPostGC();
+
+  // Start any pending finalizers.  Must be after
+  // updateStablePtrTable() and stablePtrPostGC() (see #4221).
+  RELEASE_SM_LOCK;
+  scheduleFinalizers(cap, old_weak_ptr_list);
+  ACQUIRE_SM_LOCK;
+
+  if (major_gc) {
+      nat need, got;
+      need = BLOCKS_TO_MBLOCKS(n_alloc_blocks);
+      got = mblocks_allocated;
+      /* If the amount of data remains constant, next major GC we'll
+         require (F+1)*need. We leave (F+2)*need in order to reduce
+         repeated deallocation and reallocation. */
+      need = (RtsFlags.GcFlags.oldGenFactor + 2) * need;
+      if (got > need) {
+          returnMemoryToOS(got - need);
+      }
+  }
+
   // check sanity after GC
   IF_DEBUG(sanity, checkSanity(rtsTrue));
 
@@ -771,9 +790,6 @@ SET_GCT(gc_threads[0]);
   slop = calcLiveBlocks() * BLOCK_SIZE_W - live;
   stat_endGC(allocated, live, copied, N, max_copied, avg_copied, slop);
 
-  // unlock the StablePtr table
-  stablePtrPostGC();
-
   // Guess which generation we'll collect *next* time
   initialise_N(force_major_gc);
 
@@ -1504,11 +1520,10 @@ resize_generations (void)
 
        // Auto-enable compaction when the residency reaches a
        // certain percentage of the maximum heap size (default: 30%).
-       if (RtsFlags.GcFlags.generations > 1 &&
-           (RtsFlags.GcFlags.compact ||
-            (max > 0 &&
-             oldest_gen->n_blocks > 
-             (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
+       if (RtsFlags.GcFlags.compact ||
+            (max > 0 &&
+             oldest_gen->n_blocks > 
+             (RtsFlags.GcFlags.compactThreshold * max) / 100)) {
            oldest_gen->mark = 1;
            oldest_gen->compact = 1;
 //       debugBelch("compaction: on\n", live);