Profiling by info table mode (-hi)

This profiling mode creates bands by the address of the info table for
each closure. This provides a much more fine-grained profiling output
than any of the other profiling modes.

The `-hi` profiling mode does not require a profiling build.

7 files changed, 35 insertions, 6 deletions

diff --git a/docs/users_guide/profiling.rst b/docs/users_guide/profiling.rst
index 6eb5008146..75569f6409 100644
--- a/docs/users_guide/profiling.rst
+++ b/docs/users_guide/profiling.rst
@@ -800,6 +800,11 @@ following RTS options select which break-down to use:
     Biographical profiling is described in more detail below
     (:ref:`biography-prof`).
 
+.. rts-flag:: -hi
+
+    Break down the graph by the address of the info table of a closure. This
+    profiling mode is intended to be used with :ghc-flag:`-finfo-table-map`.
+
 .. rts-flag:: -l
     :noindex:
 
diff --git a/includes/rts/EventLogFormat.h b/includes/rts/EventLogFormat.h
index 340a12d4e9..4b50adfe5b 100644
--- a/includes/rts/EventLogFormat.h
+++ b/includes/rts/EventLogFormat.h
@@ -221,7 +221,8 @@ typedef enum {
     HEAP_PROF_BREAKDOWN_TYPE_DESCR,
     HEAP_PROF_BREAKDOWN_RETAINER,
     HEAP_PROF_BREAKDOWN_BIOGRAPHY,
-    HEAP_PROF_BREAKDOWN_CLOSURE_TYPE
+    HEAP_PROF_BREAKDOWN_CLOSURE_TYPE,
+    HEAP_PROF_BREAKDOWN_INFO_TABLE
 } HeapProfBreakdown;
 
 #if !defined(EVENTLOG_CONSTANTS_ONLY)
diff --git a/includes/rts/Flags.h b/includes/rts/Flags.h
index 204ec525ac..eda961656d 100644
--- a/includes/rts/Flags.h
+++ b/includes/rts/Flags.h
@@ -132,15 +132,16 @@ typedef struct _COST_CENTRE_FLAGS {
 /* See Note [Synchronization of flags and base APIs] */
 typedef struct _PROFILING_FLAGS {
     uint32_t doHeapProfile;
-# define NO_HEAP_PROFILING	0	/* N.B. Used as indexes into arrays */
-# define HEAP_BY_CCS		1
-# define HEAP_BY_MOD		2
-# define HEAP_BY_DESCR		4
-# define HEAP_BY_TYPE		5
+# define NO_HEAP_PROFILING      0	/* N.B. Used as indexes into arrays */
+# define HEAP_BY_CCS            1
+# define HEAP_BY_MOD            2
+# define HEAP_BY_DESCR          4
+# define HEAP_BY_TYPE           5
 # define HEAP_BY_RETAINER       6
 # define HEAP_BY_LDV            7
 
 # define HEAP_BY_CLOSURE_TYPE   8
+# define HEAP_BY_INFO_TABLE     9
 
     Time        heapProfileInterval; /* time between samples */
     uint32_t    heapProfileIntervalTicks; /* ticks between samples (derived) */
diff --git a/libraries/base/GHC/RTS/Flags.hsc b/libraries/base/GHC/RTS/Flags.hsc
index 2f161c72c3..2abe5d7d85 100644
--- a/libraries/base/GHC/RTS/Flags.hsc
+++ b/libraries/base/GHC/RTS/Flags.hsc
@@ -256,6 +256,7 @@ data DoHeapProfile
     | HeapByRetainer
     | HeapByLDV
     | HeapByClosureType
+    | HeapByInfoTable
     deriving ( Show -- ^ @since 4.8.0.0
              , Generic -- ^ @since 4.15.0.0
              )
@@ -270,6 +271,7 @@ instance Enum DoHeapProfile where
     fromEnum HeapByRetainer    = #{const HEAP_BY_RETAINER}
     fromEnum HeapByLDV         = #{const HEAP_BY_LDV}
     fromEnum HeapByClosureType = #{const HEAP_BY_CLOSURE_TYPE}
+    fromEnum HeapByInfoTable   = #{const HEAP_BY_INFO_TABLE}
 
     toEnum #{const NO_HEAP_PROFILING}    = NoHeapProfiling
     toEnum #{const HEAP_BY_CCS}          = HeapByCCS
@@ -279,6 +281,7 @@ instance Enum DoHeapProfile where
     toEnum #{const HEAP_BY_RETAINER}     = HeapByRetainer
     toEnum #{const HEAP_BY_LDV}          = HeapByLDV
     toEnum #{const HEAP_BY_CLOSURE_TYPE} = HeapByClosureType
+    toEnum #{const HEAP_BY_INFO_TABLE}   = HeapByInfoTable
     toEnum e = errorWithoutStackTrace ("invalid enum for DoHeapProfile: " ++ show e)
 
 -- | Parameters of the cost-center profiler
diff --git a/rts/ProfHeap.c b/rts/ProfHeap.c
index f880f5f406..b05c34d80f 100644
--- a/rts/ProfHeap.c
+++ b/rts/ProfHeap.c
@@ -197,6 +197,9 @@ closureIdentity( const StgClosure *p )
             return closure_type_names[info->type];
         }
     }
+    case HEAP_BY_INFO_TABLE: {
+        return get_itbl(p);
+        }
 
     default:
         barf("closureIdentity");
@@ -905,6 +908,12 @@ dumpCensus( Census *census )
             traceHeapProfSampleString(0, (char *)ctr->identity,
                                       count * sizeof(W_));
             break;
+        case HEAP_BY_INFO_TABLE:
+            fprintf(hp_file, "%p", ctr->identity);
+            char str[100];
+            sprintf(str, "%p", ctr->identity);
+            traceHeapProfSampleString(0, str, count * sizeof(W_));
+            break;
 #if defined(PROFILING)
         case HEAP_BY_CCS:
             fprint_ccs(hp_file, (CostCentreStack *)ctr->identity,
diff --git a/rts/RtsFlags.c b/rts/RtsFlags.c
index bc7e86901f..fa4af7f7a6 100644
--- a/rts/RtsFlags.c
+++ b/rts/RtsFlags.c
@@ -1409,6 +1409,10 @@ error = true;
                     OPTION_UNSAFE;
                     RtsFlags.ProfFlags.doHeapProfile = HEAP_BY_CLOSURE_TYPE;
                     break;
+                  case 'i':
+                    OPTION_UNSAFE;
+                    RtsFlags.ProfFlags.doHeapProfile = HEAP_BY_INFO_TABLE;
+                    break;
                   default:
                     OPTION_SAFE;
                     PROFILING_BUILD_ONLY();
@@ -2173,6 +2177,7 @@ static bool read_heap_profiling_flag(const char *arg)
     case 'd':
     case 'Y':
     case 'y':
+    case 'i':
     case 'R':
     case 'r':
     case 'B':
@@ -2253,6 +2258,9 @@ static bool read_heap_profiling_flag(const char *arg)
         case 'y':
             RtsFlags.ProfFlags.doHeapProfile = HEAP_BY_TYPE;
             break;
+        case 'i':
+            RtsFlags.ProfFlags.doHeapProfile = HEAP_BY_INFO_TABLE;
+            break;
         case 'R':
         case 'r':
             RtsFlags.ProfFlags.doHeapProfile = HEAP_BY_RETAINER;
diff --git a/rts/eventlog/EventLog.c b/rts/eventlog/EventLog.c
index 876f1ff7b6..c1eda283f5 100644
--- a/rts/eventlog/EventLog.c
+++ b/rts/eventlog/EventLog.c
@@ -1410,6 +1410,8 @@ static HeapProfBreakdown getHeapProfBreakdown(void)
         return HEAP_PROF_BREAKDOWN_BIOGRAPHY;
     case HEAP_BY_CLOSURE_TYPE:
         return HEAP_PROF_BREAKDOWN_CLOSURE_TYPE;
+    case HEAP_BY_INFO_TABLE:
+        return HEAP_PROF_BREAKDOWN_INFO_TABLE;
     default:
         barf("getHeapProfBreakdown: unknown heap profiling mode");
     }