# Maintenance notes
This picks and describes some tools to help analyze the state of the codebase and support its maintenance.
# Analyze churn
The amount of churn, so the number of changes done to a file can be an indicator which files/parts might need refactoring.
To find churn metrics a tool such as Churn (opens new window) can be used:
gem install churn
An example output as of v1.6.0-rc2 would be:
cd src/PX4-Autopilot
churn --start_date "6 months ago"
**********************************************************************
* Revision Changes
**********************************************************************
Files
+------------------------------------------+
| file |
+------------------------------------------+
| src/modules/navigator/mission.cpp |
| src/modules/navigator/navigator_main.cpp |
| src/modules/navigator/rtl.cpp |
+------------------------------------------+
**********************************************************************
* Project Churn
**********************************************************************
Files
+---------------------------------------------------------------------------+---------------+
| file_path | times_changed |
+---------------------------------------------------------------------------+---------------+
| src/modules/mc_pos_control/mc_pos_control_main.cpp | 107 |
| src/modules/commander/commander.cpp | 67 |
| ROMFS/px4fmu_common/init.d/rcS | 52 |
| Makefile | 49 |
| src/drivers/px4fmu/fmu.cpp | 47 |
| ROMFS/px4fmu_common/init.d/rc.sensors | 40 |
| src/drivers/boards/aerofc-v1/board_config.h | 31 |
| src/modules/logger/logger.cpp | 29 |
| src/modules/navigator/navigator_main.cpp | 28 |