Fix a bug which sometimes caused extra major GCs to be performed

[ghc-hetmet.git] / rts / Capability.h

diff --git a/rts/Capability.h b/rts/Capability.h
index 478b0f1..77132e3 100644 (file)
--- a/rts/Capability.h
+++ b/rts/Capability.h
@@ -32,11 +32,7 @@ struct Capability_ {
     // code.  During STG execution, the BaseReg register always points
     // to the StgRegTable of the current Capability (&cap->r).
     StgFunTable f;
-    StgRegTable r GNU_ATTRIBUTE(packed);
-       // packed eliminates any padding between f and r.  Not strictly
-       // necessary, but it means the negative offsets for accessing
-       // the fields of f when we are in STG code are as small as
-       // possible.
+    StgRegTable r;
 
     nat no;  // capability number.
 
@@ -69,10 +65,12 @@ struct Capability_ {
     Task *suspended_ccalling_tasks;
 
     // One mutable list per generation, so we don't need to take any
-    // locks when updating an old-generation thunk.  These
-    // mini-mut-lists are moved onto the respective gen->mut_list at
-    // each GC.
+    // locks when updating an old-generation thunk.  This also lets us
+    // keep track of which closures this CPU has been mutating, so we
+    // can traverse them using the right thread during GC and avoid
+    // unnecessarily moving the data from one cache to another.
     bdescr **mut_lists;
+    bdescr **saved_mut_lists; // tmp use during GC
 
     // Context switch flag. We used to have one global flag, now one 
     // per capability. Locks required  : none (conflicts are harmless)
@@ -147,12 +145,10 @@ struct Capability_ {
 
 // Converts a *StgRegTable into a *Capability.
 //
-#define OFFSET(s_type, field) ((size_t)&(((s_type*)0)->field))
-
 INLINE_HEADER Capability *
 regTableToCapability (StgRegTable *reg)
 {
-    return (Capability *)((void *)((unsigned char*)reg - OFFSET(Capability,r)));
+    return (Capability *)((void *)((unsigned char*)reg - FIELD_OFFSET(Capability,r)));
 }
 
 // Initialise the available capabilities.