X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=rts%2Fsm%2FScav.c;h=5d156ed64c761eda4e09139b3c2ef36bfd9d0a19;hb=4e79709df545c16812b85f2c27ab3411f5a7b54f;hp=080c75014e647acfb8db1d41ce52491cc55604f2;hpb=bf1197b67163d9f5b6509cf836e07ff83cc0a063;p=ghc-hetmet.git

diff --git a/rts/sm/Scav.c b/rts/sm/Scav.c
index 080c750..5d156ed 100644
--- a/rts/sm/Scav.c
+++ b/rts/sm/Scav.c
@@ -1,6 +1,6 @@
 /* -----------------------------------------------------------------------------
  *
- * (c) The GHC Team 1998-2006
+ * (c) The GHC Team 1998-2008
  *
  * Generational garbage collector: scavenging functions
  *
@@ -16,6 +16,7 @@
 #include "Storage.h"
 #include "MBlock.h"
 #include "GC.h"
+#include "GCThread.h"
 #include "GCUtils.h"
 #include "Compact.h"
 #include "Evac.h"
@@ -31,8 +32,6 @@ static void scavenge_large_bitmap (StgPtr p,
 				   StgLargeBitmap *large_bitmap, 
 				   nat size );
 
-static void scavenge_block (bdescr *bd, StgPtr scan);
-
 
 /* Similar to scavenge_large_bitmap(), but we don't write back the
  * pointers we get back from evacuate().
@@ -133,9 +132,33 @@ scavenge_fun_srt(const StgInfoTable *info)
    Scavenge a TSO.
    -------------------------------------------------------------------------- */
 
+STATIC_INLINE void
+scavenge_TSO_link (StgTSO *tso)
+{
+    // We don't always chase the link field: TSOs on the blackhole
+    // queue are not automatically alive, so the link field is a
+    // "weak" pointer in that case.
+    if (tso->why_blocked != BlockedOnBlackHole) {
+        evacuate((StgClosure **)&tso->_link);
+    }
+}
+
 static void
 scavengeTSO (StgTSO *tso)
 {
+    rtsBool saved_eager;
+
+    if (tso->what_next == ThreadRelocated) {
+        // the only way this can happen is if the old TSO was on the
+        // mutable list.  We might have other links to this defunct
+        // TSO, so we must update its link field.
+        evacuate((StgClosure**)&tso->_link);
+        return;
+    }
+
+    saved_eager = gct->eager_promotion;
+    gct->eager_promotion = rtsFalse;
+
     if (   tso->why_blocked == BlockedOnMVar
 	|| tso->why_blocked == BlockedOnBlackHole
 	|| tso->why_blocked == BlockedOnException
@@ -144,18 +167,26 @@ scavengeTSO (StgTSO *tso)
     }
     evacuate((StgClosure **)&tso->blocked_exceptions);
     
-    // We don't always chase the link field: TSOs on the blackhole
-    // queue are not automatically alive, so the link field is a
-    // "weak" pointer in that case.
-    if (tso->why_blocked != BlockedOnBlackHole) {
-	evacuate((StgClosure **)&tso->link);
-    }
-
     // scavange current transaction record
     evacuate((StgClosure **)&tso->trec);
     
     // scavenge this thread's stack 
     scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
+
+    if (gct->failed_to_evac) {
+        tso->flags |= TSO_DIRTY;
+        scavenge_TSO_link(tso);
+    } else {
+        tso->flags &= ~TSO_DIRTY;
+        scavenge_TSO_link(tso);
+        if (gct->failed_to_evac) {
+            tso->flags |= TSO_LINK_DIRTY;
+        } else {
+            tso->flags &= ~TSO_LINK_DIRTY;
+        }
+    }
+
+    gct->eager_promotion = saved_eager;
 }
 
 /* -----------------------------------------------------------------------------
@@ -252,429 +283,6 @@ scavenge_AP (StgAP *ap)
 }
 
 /* -----------------------------------------------------------------------------
-   Scavenge a block from the given scan pointer up to bd->free.
-
-   evac_gen is set by the caller to be either zero (for a step in a
-   generation < N) or G where G is the generation of the step being
-   scavenged.  
-
-   We sometimes temporarily change evac_gen back to zero if we're
-   scavenging a mutable object where eager promotion isn't such a good
-   idea.  
-   -------------------------------------------------------------------------- */
-
-static void
-scavenge_block (bdescr *bd, StgPtr scan)
-{
-  StgPtr p, q;
-  StgInfoTable *info;
-  nat saved_evac_gen;
-
-  p = scan;
-  
-  debugTrace(DEBUG_gc, "scavenging block %p (gen %d, step %d) @ %p",
-	     bd->start, bd->gen_no, bd->step->no, scan);
-
-  gct->evac_gen = bd->gen_no;
-  saved_evac_gen = gct->evac_gen;
-  gct->failed_to_evac = rtsFalse;
-
-  // we might be evacuating into the very object that we're
-  // scavenging, so we have to check the real bd->free pointer each
-  // time around the loop.
-  while (p < bd->free) {
-
-    ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
-    info = get_itbl((StgClosure *)p);
-    
-    ASSERT(gct->thunk_selector_depth == 0);
-
-    q = p;
-    switch (info->type) {
-
-    case MVAR_CLEAN:
-    case MVAR_DIRTY:
-    { 
-	rtsBool saved_eager_promotion = gct->eager_promotion;
-
-	StgMVar *mvar = ((StgMVar *)p);
-	gct->eager_promotion = rtsFalse;
-	evacuate((StgClosure **)&mvar->head);
-	evacuate((StgClosure **)&mvar->tail);
-	evacuate((StgClosure **)&mvar->value);
-	gct->eager_promotion = saved_eager_promotion;
-
-	if (gct->failed_to_evac) {
-	    mvar->header.info = &stg_MVAR_DIRTY_info;
-	} else {
-	    mvar->header.info = &stg_MVAR_CLEAN_info;
-	}
-	p += sizeofW(StgMVar);
-	break;
-    }
-
-    case FUN_2_0:
-	scavenge_fun_srt(info);
-	evacuate(&((StgClosure *)p)->payload[1]);
-	evacuate(&((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-
-    case THUNK_2_0:
-	scavenge_thunk_srt(info);
-	evacuate(&((StgThunk *)p)->payload[1]);
-	evacuate(&((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 2;
-	break;
-
-    case CONSTR_2_0:
-	evacuate(&((StgClosure *)p)->payload[1]);
-	evacuate(&((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case THUNK_1_0:
-	scavenge_thunk_srt(info);
-	evacuate(&((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 1;
-	break;
-	
-    case FUN_1_0:
-	scavenge_fun_srt(info);
-    case CONSTR_1_0:
-	evacuate(&((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 1;
-	break;
-	
-    case THUNK_0_1:
-	scavenge_thunk_srt(info);
-	p += sizeofW(StgThunk) + 1;
-	break;
-	
-    case FUN_0_1:
-	scavenge_fun_srt(info);
-    case CONSTR_0_1:
-	p += sizeofW(StgHeader) + 1;
-	break;
-	
-    case THUNK_0_2:
-	scavenge_thunk_srt(info);
-	p += sizeofW(StgThunk) + 2;
-	break;
-	
-    case FUN_0_2:
-	scavenge_fun_srt(info);
-    case CONSTR_0_2:
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case THUNK_1_1:
-	scavenge_thunk_srt(info);
-	evacuate(&((StgThunk *)p)->payload[0]);
-	p += sizeofW(StgThunk) + 2;
-	break;
-
-    case FUN_1_1:
-	scavenge_fun_srt(info);
-    case CONSTR_1_1:
-	evacuate(&((StgClosure *)p)->payload[0]);
-	p += sizeofW(StgHeader) + 2;
-	break;
-	
-    case FUN:
-	scavenge_fun_srt(info);
-	goto gen_obj;
-
-    case THUNK:
-    {
-	StgPtr end;
-
-	scavenge_thunk_srt(info);
-	end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
-	for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
-	    evacuate((StgClosure **)p);
-	}
-	p += info->layout.payload.nptrs;
-	break;
-    }
-	
-    gen_obj:
-    case CONSTR:
-    case WEAK:
-    case STABLE_NAME:
-    {
-	StgPtr end;
-
-	end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
-	for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
-	    evacuate((StgClosure **)p);
-	}
-	p += info->layout.payload.nptrs;
-	break;
-    }
-
-    case BCO: {
-	StgBCO *bco = (StgBCO *)p;
-	evacuate((StgClosure **)&bco->instrs);
-	evacuate((StgClosure **)&bco->literals);
-	evacuate((StgClosure **)&bco->ptrs);
-	p += bco_sizeW(bco);
-	break;
-    }
-
-    case IND_PERM:
-      if (bd->gen_no != 0) {
-#ifdef PROFILING
-        // @LDV profiling
-        // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an 
-        // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
-        LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
-#endif        
-        // 
-        // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
-        //
-	SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
-
-        // We pretend that p has just been created.
-        LDV_RECORD_CREATE((StgClosure *)p);
-      }
-	// fall through 
-    case IND_OLDGEN_PERM:
-	evacuate(&((StgInd *)p)->indirectee);
-	p += sizeofW(StgInd);
-	break;
-
-    case MUT_VAR_CLEAN:
-    case MUT_VAR_DIRTY: {
-	rtsBool saved_eager_promotion = gct->eager_promotion;
-
-	gct->eager_promotion = rtsFalse;
-	evacuate(&((StgMutVar *)p)->var);
-	gct->eager_promotion = saved_eager_promotion;
-
-	if (gct->failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
-	}
-	p += sizeofW(StgMutVar);
-	break;
-    }
-
-    case CAF_BLACKHOLE:
-    case SE_CAF_BLACKHOLE:
-    case SE_BLACKHOLE:
-    case BLACKHOLE:
-	p += BLACKHOLE_sizeW();
-	break;
-
-    case THUNK_SELECTOR:
-    { 
-	StgSelector *s = (StgSelector *)p;
-	evacuate(&s->selectee);
-	p += THUNK_SELECTOR_sizeW();
-	break;
-    }
-
-    // A chunk of stack saved in a heap object
-    case AP_STACK:
-    {
-	StgAP_STACK *ap = (StgAP_STACK *)p;
-
-	evacuate(&ap->fun);
-	scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
-	p = (StgPtr)ap->payload + ap->size;
-	break;
-    }
-
-    case PAP:
-	p = scavenge_PAP((StgPAP *)p);
-	break;
-
-    case AP:
-	p = scavenge_AP((StgAP *)p);
-	break;
-
-    case ARR_WORDS:
-	// nothing to follow 
-	p += arr_words_sizeW((StgArrWords *)p);
-	break;
-
-    case MUT_ARR_PTRS_CLEAN:
-    case MUT_ARR_PTRS_DIRTY:
-	// follow everything 
-    {
-	StgPtr next;
-	rtsBool saved_eager;
-
-	// We don't eagerly promote objects pointed to by a mutable
-	// array, but if we find the array only points to objects in
-	// the same or an older generation, we mark it "clean" and
-	// avoid traversing it during minor GCs.
-	saved_eager = gct->eager_promotion;
-	gct->eager_promotion = rtsFalse;
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    evacuate((StgClosure **)p);
-	}
-	gct->eager_promotion = saved_eager;
-
-	if (gct->failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
-	}
-
-	gct->failed_to_evac = rtsTrue; // always put it on the mutable list.
-	break;
-    }
-
-    case MUT_ARR_PTRS_FROZEN:
-    case MUT_ARR_PTRS_FROZEN0:
-	// follow everything 
-    {
-	StgPtr next;
-
-	next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
-	for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
-	    evacuate((StgClosure **)p);
-	}
-
-	// If we're going to put this object on the mutable list, then
-	// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
-	if (gct->failed_to_evac) {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
-	} else {
-	    ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
-	}
-	break;
-    }
-
-    case TSO:
-    { 
-	StgTSO *tso = (StgTSO *)p;
-	rtsBool saved_eager = gct->eager_promotion;
-
-	gct->eager_promotion = rtsFalse;
-	scavengeTSO(tso);
-	gct->eager_promotion = saved_eager;
-
-	if (gct->failed_to_evac) {
-	    tso->flags |= TSO_DIRTY;
-	} else {
-	    tso->flags &= ~TSO_DIRTY;
-	}
-
-	gct->failed_to_evac = rtsTrue; // always on the mutable list
-	p += tso_sizeW(tso);
-	break;
-    }
-
-    case TVAR_WATCH_QUEUE:
-      {
-	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	gct->evac_gen = 0;
-	evacuate((StgClosure **)&wq->closure);
-	evacuate((StgClosure **)&wq->next_queue_entry);
-	evacuate((StgClosure **)&wq->prev_queue_entry);
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTVarWatchQueue);
-	break;
-      }
-
-    case TVAR:
-      {
-	StgTVar *tvar = ((StgTVar *) p);
-	gct->evac_gen = 0;
-	evacuate((StgClosure **)&tvar->current_value);
-	evacuate((StgClosure **)&tvar->first_watch_queue_entry);
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTVar);
-	break;
-      }
-
-    case TREC_HEADER:
-      {
-        StgTRecHeader *trec = ((StgTRecHeader *) p);
-        gct->evac_gen = 0;
-	evacuate((StgClosure **)&trec->enclosing_trec);
-	evacuate((StgClosure **)&trec->current_chunk);
-	evacuate((StgClosure **)&trec->invariants_to_check);
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTRecHeader);
-        break;
-      }
-
-    case TREC_CHUNK:
-      {
-	StgWord i;
-	StgTRecChunk *tc = ((StgTRecChunk *) p);
-	TRecEntry *e = &(tc -> entries[0]);
-	gct->evac_gen = 0;
-	evacuate((StgClosure **)&tc->prev_chunk);
-	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
-	  evacuate((StgClosure **)&e->tvar);
-	  evacuate((StgClosure **)&e->expected_value);
-	  evacuate((StgClosure **)&e->new_value);
-	}
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgTRecChunk);
-	break;
-      }
-
-    case ATOMIC_INVARIANT:
-      {
-        StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-        gct->evac_gen = 0;
-	evacuate(&invariant->code);
-	evacuate((StgClosure **)&invariant->last_execution);
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgAtomicInvariant);
-        break;
-      }
-
-    case INVARIANT_CHECK_QUEUE:
-      {
-        StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-        gct->evac_gen = 0;
-	evacuate((StgClosure **)&queue->invariant);
-	evacuate((StgClosure **)&queue->my_execution);
-	evacuate((StgClosure **)&queue->next_queue_entry);
-	gct->evac_gen = saved_evac_gen;
-	gct->failed_to_evac = rtsTrue; // mutable
-	p += sizeofW(StgInvariantCheckQueue);
-        break;
-      }
-
-    default:
-	barf("scavenge: unimplemented/strange closure type %d @ %p", 
-	     info->type, p);
-    }
-
-    /*
-     * We need to record the current object on the mutable list if
-     *  (a) It is actually mutable, or 
-     *  (b) It contains pointers to a younger generation.
-     * Case (b) arises if we didn't manage to promote everything that
-     * the current object points to into the current generation.
-     */
-    if (gct->failed_to_evac) {
-	gct->failed_to_evac = rtsFalse;
-	if (bd->gen_no > 0) {
-	    recordMutableGen_GC((StgClosure *)q, &generations[bd->gen_no]);
-	}
-    }
-  }
-
-  debugTrace(DEBUG_gc, "   scavenged %ld bytes", (bd->free - scan) * sizeof(W_));
-}    
-
-/* -----------------------------------------------------------------------------
    Scavenge everything on the mark stack.
 
    This is slightly different from scavenge():
@@ -687,10 +295,10 @@ scavenge_mark_stack(void)
 {
     StgPtr p, q;
     StgInfoTable *info;
-    nat saved_evac_gen;
+    step *saved_evac_step;
 
-    gct->evac_gen = oldest_gen->no;
-    saved_evac_gen = gct->evac_gen;
+    gct->evac_step = &oldest_gen->steps[0];
+    saved_evac_step = gct->evac_step;
 
 linear_scan:
     while (!mark_stack_empty()) {
@@ -700,7 +308,7 @@ linear_scan:
 	info = get_itbl((StgClosure *)p);
 	
 	q = p;
-	switch (info->type) {
+        switch (((volatile StgWord *)info)[1] & 0xffff) {
 	    
         case MVAR_CLEAN:
         case MVAR_DIRTY:
@@ -919,31 +527,18 @@ linear_scan:
 
 	case TSO:
 	{ 
-	    StgTSO *tso = (StgTSO *)p;
-	    rtsBool saved_eager = gct->eager_promotion;
-
-	    gct->eager_promotion = rtsFalse;
-	    scavengeTSO(tso);
-	    gct->eager_promotion = saved_eager;
-	    
-	    if (gct->failed_to_evac) {
-		tso->flags |= TSO_DIRTY;
-	    } else {
-		tso->flags &= ~TSO_DIRTY;
-	    }
-	    
-	    gct->failed_to_evac = rtsTrue; // always on the mutable list
+            scavengeTSO((StgTSO*)p);
 	    break;
 	}
 
 	case TVAR_WATCH_QUEUE:
 	  {
 	    StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	    gct->evac_gen = 0;
+	    gct->evac_step = 0;
             evacuate((StgClosure **)&wq->closure);
 	    evacuate((StgClosure **)&wq->next_queue_entry);
 	    evacuate((StgClosure **)&wq->prev_queue_entry);
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
 	    break;
 	  }
@@ -951,10 +546,10 @@ linear_scan:
 	case TVAR:
 	  {
 	    StgTVar *tvar = ((StgTVar *) p);
-	    gct->evac_gen = 0;
+	    gct->evac_step = 0;
 	    evacuate((StgClosure **)&tvar->current_value);
 	    evacuate((StgClosure **)&tvar->first_watch_queue_entry);
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
 	    break;
 	  }
@@ -964,14 +559,14 @@ linear_scan:
 	    StgWord i;
 	    StgTRecChunk *tc = ((StgTRecChunk *) p);
 	    TRecEntry *e = &(tc -> entries[0]);
-	    gct->evac_gen = 0;
+	    gct->evac_step = 0;
 	    evacuate((StgClosure **)&tc->prev_chunk);
 	    for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
 	      evacuate((StgClosure **)&e->tvar);
 	      evacuate((StgClosure **)&e->expected_value);
 	      evacuate((StgClosure **)&e->new_value);
 	    }
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
 	    break;
 	  }
@@ -979,11 +574,11 @@ linear_scan:
 	case TREC_HEADER:
 	  {
 	    StgTRecHeader *trec = ((StgTRecHeader *) p);
-	    gct->evac_gen = 0;
+	    gct->evac_step = 0;
 	    evacuate((StgClosure **)&trec->enclosing_trec);
 	    evacuate((StgClosure **)&trec->current_chunk);
   	    evacuate((StgClosure **)&trec->invariants_to_check);
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
 	    break;
 	  }
@@ -991,10 +586,10 @@ linear_scan:
         case ATOMIC_INVARIANT:
           {
             StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-            gct->evac_gen = 0;
+            gct->evac_step = 0;
 	    evacuate(&invariant->code);
     	    evacuate((StgClosure **)&invariant->last_execution);
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
             break;
           }
@@ -1002,11 +597,11 @@ linear_scan:
         case INVARIANT_CHECK_QUEUE:
           {
             StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-            gct->evac_gen = 0;
+            gct->evac_step = 0;
     	    evacuate((StgClosure **)&queue->invariant);
 	    evacuate((StgClosure **)&queue->my_execution);
             evacuate((StgClosure **)&queue->next_queue_entry);
-	    gct->evac_gen = saved_evac_gen;
+	    gct->evac_step = saved_evac_step;
 	    gct->failed_to_evac = rtsTrue; // mutable
             break;
           }
@@ -1018,8 +613,8 @@ linear_scan:
 
 	if (gct->failed_to_evac) {
 	    gct->failed_to_evac = rtsFalse;
-	    if (gct->evac_gen > 0) {
-		recordMutableGen_GC((StgClosure *)q, &generations[gct->evac_gen]);
+	    if (gct->evac_step) {
+		recordMutableGen_GC((StgClosure *)q, gct->evac_step->gen);
 	    }
 	}
 	
@@ -1079,7 +674,7 @@ static rtsBool
 scavenge_one(StgPtr p)
 {
     const StgInfoTable *info;
-    nat saved_evac_gen = gct->evac_gen;
+    step *saved_evac_step = gct->evac_step;
     rtsBool no_luck;
     
     ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
@@ -1251,31 +846,18 @@ scavenge_one(StgPtr p)
 
     case TSO:
     {
-	StgTSO *tso = (StgTSO *)p;
-	rtsBool saved_eager = gct->eager_promotion;
-
-	gct->eager_promotion = rtsFalse;
-	scavengeTSO(tso);
-	gct->eager_promotion = saved_eager;
-
-	if (gct->failed_to_evac) {
-	    tso->flags |= TSO_DIRTY;
-	} else {
-	    tso->flags &= ~TSO_DIRTY;
-	}
-
-	gct->failed_to_evac = rtsTrue; // always on the mutable list
+	scavengeTSO((StgTSO*)p);
 	break;
     }
   
     case TVAR_WATCH_QUEUE:
       {
 	StgTVarWatchQueue *wq = ((StgTVarWatchQueue *) p);
-	gct->evac_gen = 0;
+	gct->evac_step = 0;
         evacuate((StgClosure **)&wq->closure);
         evacuate((StgClosure **)&wq->next_queue_entry);
         evacuate((StgClosure **)&wq->prev_queue_entry);
-	gct->evac_gen = saved_evac_gen;
+	gct->evac_step = saved_evac_step;
 	gct->failed_to_evac = rtsTrue; // mutable
 	break;
       }
@@ -1283,10 +865,10 @@ scavenge_one(StgPtr p)
     case TVAR:
       {
 	StgTVar *tvar = ((StgTVar *) p);
-	gct->evac_gen = 0;
+	gct->evac_step = 0;
 	evacuate((StgClosure **)&tvar->current_value);
         evacuate((StgClosure **)&tvar->first_watch_queue_entry);
-	gct->evac_gen = saved_evac_gen;
+	gct->evac_step = saved_evac_step;
 	gct->failed_to_evac = rtsTrue; // mutable
 	break;
       }
@@ -1294,11 +876,11 @@ scavenge_one(StgPtr p)
     case TREC_HEADER:
       {
         StgTRecHeader *trec = ((StgTRecHeader *) p);
-        gct->evac_gen = 0;
+        gct->evac_step = 0;
 	evacuate((StgClosure **)&trec->enclosing_trec);
 	evacuate((StgClosure **)&trec->current_chunk);
         evacuate((StgClosure **)&trec->invariants_to_check);
-	gct->evac_gen = saved_evac_gen;
+	gct->evac_step = saved_evac_step;
 	gct->failed_to_evac = rtsTrue; // mutable
         break;
       }
@@ -1308,14 +890,14 @@ scavenge_one(StgPtr p)
 	StgWord i;
 	StgTRecChunk *tc = ((StgTRecChunk *) p);
 	TRecEntry *e = &(tc -> entries[0]);
-	gct->evac_gen = 0;
+	gct->evac_step = 0;
 	evacuate((StgClosure **)&tc->prev_chunk);
 	for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
 	  evacuate((StgClosure **)&e->tvar);
 	  evacuate((StgClosure **)&e->expected_value);
 	  evacuate((StgClosure **)&e->new_value);
 	}
-	gct->evac_gen = saved_evac_gen;
+	gct->evac_step = saved_evac_step;
 	gct->failed_to_evac = rtsTrue; // mutable
 	break;
       }
@@ -1323,10 +905,10 @@ scavenge_one(StgPtr p)
     case ATOMIC_INVARIANT:
     {
       StgAtomicInvariant *invariant = ((StgAtomicInvariant *) p);
-      gct->evac_gen = 0;
+      gct->evac_step = 0;
       evacuate(&invariant->code);
       evacuate((StgClosure **)&invariant->last_execution);
-      gct->evac_gen = saved_evac_gen;
+      gct->evac_step = saved_evac_step;
       gct->failed_to_evac = rtsTrue; // mutable
       break;
     }
@@ -1334,11 +916,11 @@ scavenge_one(StgPtr p)
     case INVARIANT_CHECK_QUEUE:
     {
       StgInvariantCheckQueue *queue = ((StgInvariantCheckQueue *) p);
-      gct->evac_gen = 0;
+      gct->evac_step = 0;
       evacuate((StgClosure **)&queue->invariant);
       evacuate((StgClosure **)&queue->my_execution);
       evacuate((StgClosure **)&queue->next_queue_entry);
-      gct->evac_gen = saved_evac_gen;
+      gct->evac_step = saved_evac_step;
       gct->failed_to_evac = rtsTrue; // mutable
       break;
     }
@@ -1413,7 +995,7 @@ scavenge_mutable_list(generation *gen)
 
     bd = gen->saved_mut_list;
 
-    gct->evac_gen = gen->no;
+    gct->evac_step = &gen->steps[0];
     for (; bd != NULL; bd = bd->link) {
 	for (q = bd->start; q < bd->free; q++) {
 	    p = (StgPtr)*q;
@@ -1453,14 +1035,17 @@ scavenge_mutable_list(generation *gen)
 	    case TSO: {
 		StgTSO *tso = (StgTSO *)p;
 		if ((tso->flags & TSO_DIRTY) == 0) {
-		    // A clean TSO: we don't have to traverse its
-		    // stack.  However, we *do* follow the link field:
-		    // we don't want to have to mark a TSO dirty just
-		    // because we put it on a different queue.
-		    if (tso->why_blocked != BlockedOnBlackHole) {
-			evacuate((StgClosure **)&tso->link);
-		    }
-		    recordMutableGen_GC((StgClosure *)p,gen);
+                    // Must be on the mutable list because its link
+                    // field is dirty.
+                    ASSERT(tso->flags & TSO_LINK_DIRTY);
+
+                    scavenge_TSO_link(tso);
+                    if (gct->failed_to_evac) {
+                        recordMutableGen_GC((StgClosure *)p,gen);
+                        gct->failed_to_evac = rtsFalse;
+                    } else {
+                        tso->flags &= ~TSO_LINK_DIRTY;
+                    }
 		    continue;
 		}
 	    }
@@ -1477,7 +1062,7 @@ scavenge_mutable_list(generation *gen)
     }
 
     // free the old mut_list
-    freeChain(gen->saved_mut_list);
+    freeChain_sync(gen->saved_mut_list);
     gen->saved_mut_list = NULL;
 }
 
@@ -1495,24 +1080,23 @@ scavenge_static(void)
   StgClosure* p;
   const StgInfoTable *info;
 
+  debugTrace(DEBUG_gc, "scavenging static objects");
+
   /* Always evacuate straight to the oldest generation for static
    * objects */
-  gct->evac_gen = oldest_gen->no;
+  gct->evac_step = &oldest_gen->steps[0];
 
   /* keep going until we've scavenged all the objects on the linked
      list... */
 
   while (1) {
       
-    ACQUIRE_SPIN_LOCK(&static_objects_sync);
-    
     /* get the next static object from the list.  Remember, there might
      * be more stuff on this list after each evacuation...
      * (static_objects is a global)
      */
-    p = static_objects;
+    p = gct->static_objects;
     if (p == END_OF_STATIC_LIST) {
-    	  RELEASE_SPIN_LOCK(&static_objects_sync);
     	  break;
     }
     
@@ -1527,11 +1111,9 @@ scavenge_static(void)
     /* Take this object *off* the static_objects list,
      * and put it on the scavenged_static_objects list.
      */
-    static_objects = *STATIC_LINK(info,p);
-    *STATIC_LINK(info,p) = scavenged_static_objects;
-    scavenged_static_objects = p;
-    
-    RELEASE_SPIN_LOCK(&static_objects_sync);
+    gct->static_objects = *STATIC_LINK(info,p);
+    *STATIC_LINK(info,p) = gct->scavenged_static_objects;
+    gct->scavenged_static_objects = p;
     
     switch (info -> type) {
       
@@ -1669,17 +1251,22 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 	// discarding it.
     {
         nat type;
-        type = get_itbl(((StgUpdateFrame *)p)->updatee)->type;
-	if (type == IND) {
-	    ((StgUpdateFrame *)p)->updatee->header.info = 
-		(StgInfoTable *)&stg_IND_PERM_info;
-	} else if (type == IND_OLDGEN) {
-	    ((StgUpdateFrame *)p)->updatee->header.info = 
-		(StgInfoTable *)&stg_IND_OLDGEN_PERM_info;
-        }            
-	evacuate(&((StgUpdateFrame *)p)->updatee);
-	p += sizeofW(StgUpdateFrame);
-	continue;
+        const StgInfoTable *i;
+
+        i = ((StgUpdateFrame *)p)->updatee->header.info;
+        if (!IS_FORWARDING_PTR(i)) {
+            type = get_itbl(((StgUpdateFrame *)p)->updatee)->type;
+            if (type == IND) {
+                ((StgUpdateFrame *)p)->updatee->header.info = 
+                    (StgInfoTable *)&stg_IND_PERM_info;
+            } else if (type == IND_OLDGEN) {
+                ((StgUpdateFrame *)p)->updatee->header.info = 
+                    (StgInfoTable *)&stg_IND_OLDGEN_PERM_info;
+            }            
+            evacuate(&((StgUpdateFrame *)p)->updatee);
+            p += sizeofW(StgUpdateFrame);
+            continue;
+        }
     }
 
       // small bitmap (< 32 entries, or 64 on a 64-bit machine) 
@@ -1774,9 +1361,9 @@ scavenge_stack(StgPtr p, StgPtr stack_end)
 /*-----------------------------------------------------------------------------
   scavenge the large object list.
 
-  evac_gen set by caller; similar games played with evac_gen as with
+  evac_step set by caller; similar games played with evac_step as with
   scavenge() - see comment at the top of scavenge().  Most large
-  objects are (repeatedly) mutable, so most of the time evac_gen will
+  objects are (repeatedly) mutable, so most of the time evac_step will
   be zero.
   --------------------------------------------------------------------------- */
 
@@ -1786,7 +1373,7 @@ scavenge_large (step_workspace *ws)
     bdescr *bd;
     StgPtr p;
 
-    gct->evac_gen = ws->stp->gen_no;
+    gct->evac_step = ws->step;
 
     bd = ws->todo_large_objects;
     
@@ -1798,124 +1385,114 @@ scavenge_large (step_workspace *ws)
 	// the front when evacuating.
 	ws->todo_large_objects = bd->link;
 	
-	ACQUIRE_SPIN_LOCK(&ws->stp->sync_large_objects);
-	dbl_link_onto(bd, &ws->stp->scavenged_large_objects);
-	ws->stp->n_scavenged_large_blocks += bd->blocks;
-	RELEASE_SPIN_LOCK(&ws->stp->sync_large_objects);
+	ACQUIRE_SPIN_LOCK(&ws->step->sync_large_objects);
+	dbl_link_onto(bd, &ws->step->scavenged_large_objects);
+	ws->step->n_scavenged_large_blocks += bd->blocks;
+	RELEASE_SPIN_LOCK(&ws->step->sync_large_objects);
 	
 	p = bd->start;
 	if (scavenge_one(p)) {
-	    if (ws->stp->gen_no > 0) {
-		recordMutableGen_GC((StgClosure *)p, ws->stp->gen);
+	    if (ws->step->gen_no > 0) {
+		recordMutableGen_GC((StgClosure *)p, ws->step->gen);
 	    }
 	}
+
+        // stats
+        gct->scanned += closure_sizeW((StgClosure*)p);
     }
 }
 
 /* ----------------------------------------------------------------------------
-   Find the oldest full block to scavenge, and scavenge it.
+   Scavenge a block
    ------------------------------------------------------------------------- */
 
-static rtsBool
-scavenge_find_global_work (void)
-{
-    bdescr *bd;
-    int g, s;
-    rtsBool flag;
-    step_workspace *ws;
+#undef PARALLEL_GC
+#include "Scav.c-inc"
 
-    flag = rtsFalse;
-    for (g = RtsFlags.GcFlags.generations; --g >= 0; ) {
-	for (s = generations[g].n_steps; --s >= 0; ) {
-	    if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { 
-		continue; 
-	    }
-	    ws = &gct->steps[g][s];
-
-	    // If we have any large objects to scavenge, do them now.
-	    if (ws->todo_large_objects) {
-		scavenge_large(ws);
-		flag = rtsTrue;
-	    }
-
-	    if ((bd = grab_todo_block(ws)) != NULL) {
-		// no need to assign this to ws->scan_bd, we're going
-		// to scavenge the whole thing and then push it on
-		// our scavd list.  This saves pushing out the
-		// scan_bd block, which might be partial.
-		scavenge_block(bd, bd->start);
-		push_scan_block(bd, ws);
-		return rtsTrue;
-	    }
-
-	    if (flag) return rtsTrue;
-	}
-    }
-    return rtsFalse;
-}
+#ifdef THREADED_RTS
+#define PARALLEL_GC
+#include "Scav.c-inc"
+#endif
 
 /* ----------------------------------------------------------------------------
-   Look for local work to do.
-
-   We can have outstanding scavenging to do if, for any of the workspaces,
-
-     - the scan block is the same as the todo block, and new objects
-       have been evacuated to the todo block.
-
-     - the scan block *was* the same as the todo block, but the todo
-       block filled up and a new one has been allocated.
+   Look for work to do.
+
+   We look for the oldest step that has either a todo block that can
+   be scanned, or a block of work on the global queue that we can
+   scan.
+
+   It is important to take work from the *oldest* generation that we
+   has work available, because that minimizes the likelihood of
+   evacuating objects into a young generation when they should have
+   been eagerly promoted.  This really does make a difference (the
+   cacheprof benchmark is one that is affected).
+
+   We also want to scan the todo block if possible before grabbing
+   work from the global queue, the reason being that we don't want to
+   steal work from the global queue and starve other threads if there
+   is other work we can usefully be doing.
    ------------------------------------------------------------------------- */
 
 static rtsBool
-scavenge_find_local_work (void)
+scavenge_find_work (void)
 {
-    int g, s;
+    int s;
     step_workspace *ws;
-    rtsBool flag;
+    rtsBool did_something, did_anything;
+    bdescr *bd;
 
-    flag = rtsFalse;
-    for (g = RtsFlags.GcFlags.generations; --g >= 0; ) {
-	for (s = generations[g].n_steps; --s >= 0; ) {
-	    if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { 
-		continue; 
-	    }
-	    ws = &gct->steps[g][s];
-
-	    // If we have a todo block and no scan block, start
-	    // scanning the todo block.
-	    if (ws->scan_bd == NULL && ws->todo_bd != NULL)
-	    {
-		ws->scan_bd = ws->todo_bd;
-		ws->scan = ws->scan_bd->start;
-	    }
+    gct->scav_find_work++;
 
-	    // If we have a scan block with some work to do,
-	    // scavenge everything up to the free pointer.
-	    if (ws->scan != NULL && ws->scan < ws->scan_bd->free)
-	    {
-		scavenge_block(ws->scan_bd, ws->scan);
-		ws->scan = ws->scan_bd->free;
-		flag = rtsTrue;
-	    }
+    did_anything = rtsFalse;
 
-	    if (ws->scan_bd != NULL && ws->scan == ws->scan_bd->free
-		&& ws->scan_bd != ws->todo_bd)
-	    {
-		// we're not going to evac any more objects into
-		// this block, so push it now.
-		push_scan_block(ws->scan_bd, ws);
-		ws->scan_bd = NULL;
-		ws->scan = NULL;
-                // we might be able to scan the todo block now.  But
-                // don't do it right away: there might be full blocks
-		// waiting to be scanned as a result of scavenge_block above.
-		flag = rtsTrue; 
-	    }
+loop:
+    did_something = rtsFalse;
+    for (s = total_steps-1; s >= 0; s--) {
+        if (s == 0 && RtsFlags.GcFlags.generations > 1) { 
+            continue; 
+        }
+        ws = &gct->steps[s];
+        
+        gct->scan_bd = NULL;
+
+        // If we have a scan block with some work to do,
+        // scavenge everything up to the free pointer.
+        if (ws->todo_bd->u.scan < ws->todo_free)
+        {
+            if (n_gc_threads == 1) {
+                scavenge_block1(ws->todo_bd);
+            } else {
+                scavenge_block(ws->todo_bd);
+            }
+            did_something = rtsTrue;
+            break;
+        }
 
-	    if (flag) return rtsTrue;
-	}
+        // If we have any large objects to scavenge, do them now.
+        if (ws->todo_large_objects) {
+            scavenge_large(ws);
+            did_something = rtsTrue;
+            break;
+        }
+
+        if ((bd = grab_todo_block(ws)) != NULL) {
+            if (n_gc_threads == 1) {
+                scavenge_block1(bd);
+            } else {
+                scavenge_block(bd);
+            }
+            did_something = rtsTrue;
+            break;
+        }
     }
-    return rtsFalse;
+
+    if (did_something) {
+        did_anything = rtsTrue;
+        goto loop;
+    }
+    // only return when there is no more work to do
+
+    return did_anything;
 }
 
 /* ----------------------------------------------------------------------------
@@ -1931,8 +1508,8 @@ loop:
     work_to_do = rtsFalse;
 
     // scavenge static objects 
-    if (major_gc && static_objects != END_OF_STATIC_LIST) {
-	IF_DEBUG(sanity, checkStaticObjects(static_objects));
+    if (major_gc && gct->static_objects != END_OF_STATIC_LIST) {
+	IF_DEBUG(sanity, checkStaticObjects(gct->static_objects));
 	scavenge_static();
     }
     
@@ -1948,8 +1525,7 @@ loop:
     // local work.  Only if all the global work has been exhausted
     // do we start scavenging the fragments of blocks in the local
     // workspaces.
-    if (scavenge_find_global_work()) goto loop;
-    if (scavenge_find_local_work())  goto loop;
+    if (scavenge_find_work()) goto loop;
     
     if (work_to_do) goto loop;
 }
@@ -1957,16 +1533,13 @@ loop:
 rtsBool
 any_work (void)
 {
-    int g, s;
+    int s;
     step_workspace *ws;
 
+    gct->any_work++;
+
     write_barrier();
 
-    // scavenge static objects 
-    if (major_gc && static_objects != END_OF_STATIC_LIST) {
-	return rtsTrue;
-    }
-    
     // scavenge objects in compacted generation
     if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
 	(mark_stack_bdescr != NULL && !mark_stack_empty())) {
@@ -1976,16 +1549,16 @@ any_work (void)
     // Check for global work in any step.  We don't need to check for
     // local work, because we have already exited scavenge_loop(),
     // which means there is no local work for this thread.
-    for (g = RtsFlags.GcFlags.generations; --g >= 0; ) {
-	for (s = generations[g].n_steps; --s >= 0; ) {
-	    if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { 
-		continue; 
-	    }
-	    ws = &gct->steps[g][s];
-	    if (ws->todo_large_objects) return rtsTrue;
-	    if (ws->stp->todos) return rtsTrue;
-	}
+    for (s = total_steps-1; s >= 0; s--) {
+        if (s == 0 && RtsFlags.GcFlags.generations > 1) { 
+            continue; 
+        }
+        ws = &gct->steps[s];
+        if (ws->todo_large_objects) return rtsTrue;
+        if (ws->step->todos) return rtsTrue;
     }
 
+    gct->no_work++;
+
     return rtsFalse;
 }