Profiling: Allow heap profiling to be controlled dynamically.

This patch exposes three new functions in `GHC.Profiling` which allow
heap profiling to be enabled and disabled dynamically.

1. startHeapProfTimer - Starts heap profiling with the given RTS options
2. stopHeapProfTimer  - Stops heap profiling
3. requestHeapCensus  - Perform a heap census on the next context
                        switch, regardless of whether the timer is enabled or not.

2 files changed, 25 insertions, 0 deletions

diff --git a/includes/rts/Flags.h b/includes/rts/Flags.h
index 735605b2ba..204ec525ac 100644
--- a/includes/rts/Flags.h
+++ b/includes/rts/Flags.h
@@ -144,6 +144,7 @@ typedef struct _PROFILING_FLAGS {
 
     Time        heapProfileInterval; /* time between samples */
     uint32_t    heapProfileIntervalTicks; /* ticks between samples (derived) */
+    bool        startHeapProfileAtStartup; /* true if we start profiling from program startup */
 
 
     bool		showCCSOnException;
diff --git a/includes/rts/prof/Heap.h b/includes/rts/prof/Heap.h
new file mode 100644
index 0000000000..90700c809b
--- /dev/null
+++ b/includes/rts/prof/Heap.h
@@ -0,0 +1,24 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The University of Glasgow, 2009
+ *
+ * Heap Census Profiling
+ *
+ * Do not #include this file directly: #include "Rts.h" instead.
+ *
+ * To understand the structure of the RTS headers, see the wiki:
+ *   https://gitlab.haskell.org/ghc/ghc/wikis/commentary/source-tree/includes
+ *
+ * ---------------------------------------------------------------------------*/
+
+#pragma once
+
+/* -----------------------------------------------------------------------------
+ * Fine-grained control over heap census profiling which can be called from
+ * Haskell to restrict the profile to portion(s) of the execution.
+ * See the module GHC.Profiling.
+ * ---------------------------------------------------------------------------*/
+
+void requestHeapCensus ( void );
+void startHeapProfTimer ( void );
+void stopHeapProfTimer ( void );