Add a proper write barrier for MVars

Previously MVars were always on the mutable list of the old
generation, which meant every MVar was visited during every minor GC.
With lots of MVars hanging around, this gets expensive.  We addressed
this problem for MUT_VARs (aka IORefs) a while ago, the solution is to
use a traditional GC write-barrier when the object is modified.  This
patch does the same thing for MVars.

TVars are still done the old way, they could probably benefit from the
same treatment too.

3 files changed, 33 insertions, 29 deletions

diff --git a/includes/ClosureTypes.h b/includes/ClosureTypes.h
index 3765801a3c..b7bebd6c6b 100644
--- a/includes/ClosureTypes.h
+++ b/includes/ClosureTypes.h
@@ -66,32 +66,33 @@
 #define BLACKHOLE	        42
 #define SE_BLACKHOLE		43
 #define SE_CAF_BLACKHOLE	44
-#define MVAR		        45
-#define ARR_WORDS	        46
-#define MUT_ARR_PTRS_CLEAN      47
-#define MUT_ARR_PTRS_DIRTY      48
-#define MUT_ARR_PTRS_FROZEN0    49
-#define MUT_ARR_PTRS_FROZEN     50
-#define MUT_VAR_CLEAN	        51
-#define MUT_VAR_DIRTY	        52
-#define WEAK		        53
-#define STABLE_NAME	        54
-#define TSO		        55
-#define BLOCKED_FETCH	        56
-#define FETCH_ME                57
-#define FETCH_ME_BQ             58
-#define RBH                     59
-#define EVACUATED               60
-#define REMOTE_REF              61
-#define TVAR_WATCH_QUEUE        62
-#define INVARIANT_CHECK_QUEUE   63
-#define ATOMIC_INVARIANT        64
-#define TVAR                    65
-#define TREC_CHUNK              66
-#define TREC_HEADER             67
-#define ATOMICALLY_FRAME        68
-#define CATCH_RETRY_FRAME       69
-#define CATCH_STM_FRAME         70
-#define N_CLOSURE_TYPES         71
+#define MVAR_CLEAN	        45
+#define MVAR_DIRTY	        46
+#define ARR_WORDS	        47
+#define MUT_ARR_PTRS_CLEAN      48
+#define MUT_ARR_PTRS_DIRTY      49
+#define MUT_ARR_PTRS_FROZEN0    50
+#define MUT_ARR_PTRS_FROZEN     51
+#define MUT_VAR_CLEAN	        52
+#define MUT_VAR_DIRTY	        53
+#define WEAK		        54
+#define STABLE_NAME	        55
+#define TSO		        56
+#define BLOCKED_FETCH	        57
+#define FETCH_ME                58
+#define FETCH_ME_BQ             59
+#define RBH                     60
+#define EVACUATED               61
+#define REMOTE_REF              62
+#define TVAR_WATCH_QUEUE        63
+#define INVARIANT_CHECK_QUEUE   64
+#define ATOMIC_INVARIANT        65
+#define TVAR                    66
+#define TREC_CHUNK              67
+#define TREC_HEADER             68
+#define ATOMICALLY_FRAME        69
+#define CATCH_RETRY_FRAME       70
+#define CATCH_STM_FRAME         71
+#define N_CLOSURE_TYPES         72
 
 #endif /* CLOSURETYPES_H */
diff --git a/includes/RtsExternal.h b/includes/RtsExternal.h
index 6c1f71e3d1..39a22fd3a8 100644
--- a/includes/RtsExternal.h
+++ b/includes/RtsExternal.h
@@ -124,5 +124,8 @@ extern void performMajorGC(void);
 extern HsInt64 getAllocations( void );
 extern void revertCAFs( void );
 extern void dirty_MUT_VAR(StgRegTable *reg, StgClosure *p);
+extern void dirty_MVAR(StgRegTable *reg, StgClosure *p);
+
+extern void dirty_TSO(StgClosure *tso);
 
 #endif /*  RTSEXTERNAL_H */
diff --git a/includes/StgMiscClosures.h b/includes/StgMiscClosures.h
index ea9e8059d0..a99ff72a22 100644
--- a/includes/StgMiscClosures.h
+++ b/includes/StgMiscClosures.h
@@ -99,8 +99,8 @@ RTS_INFO(stg_EVACUATED_info);
 RTS_INFO(stg_WEAK_info);
 RTS_INFO(stg_DEAD_WEAK_info);
 RTS_INFO(stg_STABLE_NAME_info);
-RTS_INFO(stg_FULL_MVAR_info);
-RTS_INFO(stg_EMPTY_MVAR_info);
+RTS_INFO(stg_MVAR_CLEAN_info);
+RTS_INFO(stg_MVAR_DIRTY_info);
 RTS_INFO(stg_TSO_info);
 RTS_INFO(stg_ARR_WORDS_info);
 RTS_INFO(stg_MUT_ARR_WORDS_info);