Experimental "mark-region" strategy for the old generation
[ghc-hetmet.git] / rts / sm / GC.c
index b71079b..165c706 100644 (file)
@@ -49,6 +49,7 @@
 #include "GCUtils.h"
 #include "MarkWeak.h"
 #include "Sparks.h"
+#include "Sweep.h"
 
 #include <string.h> // for memset()
 #include <unistd.h>
@@ -288,10 +289,13 @@ GarbageCollect ( rtsBool force_major_gc )
   /* Allocate a mark stack if we're doing a major collection.
    */
   if (major_gc) {
-      mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
+      nat mark_stack_blocks;
+      mark_stack_blocks = stg_max(MARK_STACK_BLOCKS, 
+                                  oldest_gen->steps[0].n_old_blocks / 100);
+      mark_stack_bdescr = allocGroup(mark_stack_blocks);
       mark_stack = (StgPtr *)mark_stack_bdescr->start;
       mark_sp    = mark_stack;
-      mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
+      mark_splim = mark_stack + (mark_stack_blocks * BLOCK_SIZE_W);
   } else {
       mark_stack_bdescr = NULL;
   }
@@ -485,9 +489,12 @@ GarbageCollect ( rtsBool force_major_gc )
       }
   }
 
-  // Finally: compaction of the oldest generation.
-  if (major_gc && oldest_gen->steps[0].is_compacted) {
-      compact(gct->scavenged_static_objects);
+  // Finally: compact or sweep the oldest generation.
+  if (major_gc && oldest_gen->steps[0].mark) {
+      if (oldest_gen->steps[0].compact) 
+          compact(gct->scavenged_static_objects);
+      else
+          sweep(&oldest_gen->steps[0]);
   }
 
   IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
@@ -542,7 +549,7 @@ GarbageCollect ( rtsBool force_major_gc )
     }
 
     for (s = 0; s < generations[g].n_steps; s++) {
-      bdescr *next;
+      bdescr *next, *prev;
       stp = &generations[g].steps[s];
 
       // for generations we collected... 
@@ -553,29 +560,48 @@ GarbageCollect ( rtsBool force_major_gc )
         * freed blocks will probaby be quickly recycled.
         */
        if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
-           if (stp->is_compacted)
+           if (stp->mark)
             {
                // tack the new blocks on the end of the existing blocks
                if (stp->old_blocks != NULL) {
+
+                    prev = NULL;
                    for (bd = stp->old_blocks; bd != NULL; bd = next) {
-                        stp->n_words += bd->free - bd->start;
-
-                       // NB. this step might not be compacted next
-                       // time, so reset the BF_COMPACTED flags.
-                       // They are set before GC if we're going to
-                       // compact.  (search for BF_COMPACTED above).
-                       bd->flags &= ~BF_COMPACTED;
-
-                        // between GCs, all blocks in the heap except
-                        // for the nursery have the BF_EVACUATED flag set.
-                        bd->flags |= BF_EVACUATED;
-
-                       next = bd->link;
-                       if (next == NULL) {
-                           bd->link = stp->blocks;
-                       }
+
+                        next = bd->link;
+
+                        if (!(bd->flags & BF_MARKED))
+                        {
+                            if (prev == NULL) {
+                                stp->old_blocks = next;
+                            } else {
+                                prev->link = next;
+                            }
+                            freeGroup(bd);
+                            stp->n_old_blocks--;
+                        }
+                        else
+                        {
+                            stp->n_words += bd->free - bd->start;
+
+                            // NB. this step might not be compacted next
+                            // time, so reset the BF_MARKED flags.
+                            // They are set before GC if we're going to
+                            // compact.  (search for BF_MARKED above).
+                            bd->flags &= ~BF_MARKED;
+                            
+                            // between GCs, all blocks in the heap except
+                            // for the nursery have the BF_EVACUATED flag set.
+                            bd->flags |= BF_EVACUATED;
+
+                            prev = bd;
+                        }
                    }
-                   stp->blocks = stp->old_blocks;
+
+                    if (prev != NULL) {
+                        prev->link = stp->blocks;
+                        stp->blocks = stp->old_blocks;
+                    }
                }
                // add the new blocks to the block tally
                stp->n_blocks += stp->n_old_blocks;
@@ -1144,6 +1170,7 @@ init_collected_gen (nat g, nat n_threads)
        stp->blocks       = NULL;
        stp->n_blocks     = 0;
        stp->n_words      = 0;
+       stp->live_estimate = 0;
 
        // we don't have any to-be-scavenged blocks yet
        stp->todos = NULL;
@@ -1165,7 +1192,7 @@ init_collected_gen (nat g, nat n_threads)
        }
 
        // for a compacted step, we need to allocate the bitmap
-       if (stp->is_compacted) {
+       if (stp->mark) {
            nat bitmap_size; // in bytes
            bdescr *bitmap_bdescr;
            StgWord *bitmap;
@@ -1190,12 +1217,14 @@ init_collected_gen (nat g, nat n_threads)
                    bd->u.bitmap = bitmap;
                    bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
                    
-                   // Also at this point we set the BF_COMPACTED flag
+                   // Also at this point we set the BF_MARKED flag
                    // for this block.  The invariant is that
-                   // BF_COMPACTED is always unset, except during GC
+                   // BF_MARKED is always unset, except during GC
                    // when it is set on those blocks which will be
                    // compacted.
-                   bd->flags |= BF_COMPACTED;
+                    if (!(bd->flags & BF_FRAGMENTED)) {
+                        bd->flags |= BF_MARKED;
+                    }
                }
            }
        }
@@ -1425,13 +1454,18 @@ resize_generations (void)
     nat g;
 
     if (major_gc && RtsFlags.GcFlags.generations > 1) {
-       nat live, size, min_alloc;
+       nat live, size, min_alloc, words;
        nat max  = RtsFlags.GcFlags.maxHeapSize;
        nat gens = RtsFlags.GcFlags.generations;
        
        // live in the oldest generations
-       live = (oldest_gen->steps[0].n_words + BLOCK_SIZE_W - 1) / BLOCK_SIZE_W+
-           oldest_gen->steps[0].n_large_blocks;
+        if (oldest_gen->steps[0].live_estimate != 0) {
+            words = oldest_gen->steps[0].live_estimate;
+        } else {
+            words = oldest_gen->steps[0].n_words;
+        }
+        live = (words + BLOCK_SIZE_W - 1) / BLOCK_SIZE_W +
+            oldest_gen->steps[0].n_large_blocks;
        
        // default max size for all generations except zero
        size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
@@ -1448,13 +1482,19 @@ resize_generations (void)
             (max > 0 &&
              oldest_gen->steps[0].n_blocks > 
              (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
-           oldest_gen->steps[0].is_compacted = 1;
+           oldest_gen->steps[0].mark = 1;
+           oldest_gen->steps[0].compact = 1;
 //       debugBelch("compaction: on\n", live);
        } else {
-           oldest_gen->steps[0].is_compacted = 0;
+           oldest_gen->steps[0].mark = 0;
+           oldest_gen->steps[0].compact = 0;
 //       debugBelch("compaction: off\n", live);
        }
 
+        if (RtsFlags.GcFlags.sweep) {
+           oldest_gen->steps[0].mark = 1;
+        }
+
        // if we're going to go over the maximum heap size, reduce the
        // size of the generations accordingly.  The calculation is
        // different if compaction is turned on, because we don't need
@@ -1468,7 +1508,7 @@ resize_generations (void)
                heapOverflow();
            }
            
-           if (oldest_gen->steps[0].is_compacted) {
+           if (oldest_gen->steps[0].compact) {
                if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
                    size = (max - min_alloc) / ((gens - 1) * 2 - 1);
                }