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.

4 files changed, 47 insertions, 0 deletions

diff --git a/testsuite/tests/profiling/should_run/all.T b/testsuite/tests/profiling/should_run/all.T
index fbe1379e92..9f1fa67e1e 100644
--- a/testsuite/tests/profiling/should_run/all.T
+++ b/testsuite/tests/profiling/should_run/all.T
@@ -8,6 +8,12 @@ test('heapprof002',
 
 test('T11489', [req_profiling], makefile_test, ['T11489'])
 
+test('dynamic-prof', [], compile_and_run, [''])
+
+test('dynamic-prof2', [only_ways(['normal']), extra_run_opts('+RTS -hT --no-automatic-heap-samples')], compile_and_run, [''])
+
+test('dynamic-prof3', [only_ways(['normal']), extra_run_opts('+RTS -hT --no-automatic-heap-samples')], compile_and_run, [''])
+
 # Below this line, run tests only with profiling ways.
 setTestOpts(req_profiling)
 setTestOpts(extra_ways(['prof', 'ghci-ext-prof']))
diff --git a/testsuite/tests/profiling/should_run/dynamic-prof.hs b/testsuite/tests/profiling/should_run/dynamic-prof.hs
new file mode 100644
index 0000000000..243e094877
--- /dev/null
+++ b/testsuite/tests/profiling/should_run/dynamic-prof.hs
@@ -0,0 +1,13 @@
+{-# LANGUAGE BangPatterns #-}
+module Main where
+
+import GHC.Profiling
+import Control.Exception
+
+main = do
+  let !t = [0..1000000]
+  evaluate (length t)
+  requestHeapCensus
+  evaluate (length t)
+
+
diff --git a/testsuite/tests/profiling/should_run/dynamic-prof2.hs b/testsuite/tests/profiling/should_run/dynamic-prof2.hs
new file mode 100644
index 0000000000..243e094877
--- /dev/null
+++ b/testsuite/tests/profiling/should_run/dynamic-prof2.hs
@@ -0,0 +1,13 @@
+{-# LANGUAGE BangPatterns #-}
+module Main where
+
+import GHC.Profiling
+import Control.Exception
+
+main = do
+  let !t = [0..1000000]
+  evaluate (length t)
+  requestHeapCensus
+  evaluate (length t)
+
+
diff --git a/testsuite/tests/profiling/should_run/dynamic-prof3.hs b/testsuite/tests/profiling/should_run/dynamic-prof3.hs
new file mode 100644
index 0000000000..f5a17bef8d
--- /dev/null
+++ b/testsuite/tests/profiling/should_run/dynamic-prof3.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE BangPatterns #-}
+module Main where
+
+import GHC.Profiling
+import Control.Exception
+
+main = do
+  startHeapProfTimer
+  let !t = [0..1000000]
+  evaluate (length t)
+  requestHeapCensus
+  evaluate (length t)
+  stopHeapProfTimer
+
+