mach python profiling.diff

diff --git a/mach b/mach
--- a/mach
+++ b/mach
@@ -83,19 +83,19 @@ py2commands="
 
 run_py() {
     # Try to run a specific Python interpreter. Fall back to the system
     # default Python if the specific interpreter couldn't be found.
     py_executable="$1"
     shift
     if which "$py_executable" > /dev/null
     then
-        exec "$py_executable" "$0" "$@"
+        exec "$py_executable" -m cProfile -s cumulative "$0" "$@"
     elif [ "$py_executable" = "python2.7" ]; then
-        exec python "$0" "$@"
+        exec python  -m cProfile -s cumulative "$0" "$@"
     else
         echo "This mach command requires $py_executable, which wasn't found on the system!"
         exit 1
     fi
 }
 
 first_arg=$1
 if [ "$first_arg" = "help" ]; then