The data manager dynamically allocates relatively small work item blocks
on an as needed basis. It never frees these, instead maintaining then in
a list of available block for reuse when needed. Even if these blocks
are small, the are required at non-deterministic times and can end up
scattered in memory thus causing memory fragmentation. In order to
mitigate this problems work item blocks are allocated in groups of 8 in
contiguous memory to reduce the number of scattered memory allocations.
In reality, based on current usage, rarely will more than one group of 8
be allocated.
Introduce SYS_RESTART_TYPE parameter having one of 3 values: boot
restart, inflight restart, or unknown restart, and defaulting to unknown
restart.
px4io.cpp sets this parameter according to the type of restart detected.
dataman.c retrieves this parameter and clears data entries according to
their persistence level. Does nothing if unknown restart.
When the data manager was first designed each file record contained a 2
byte header and an 126 byte data section, resulting in a record length
of 128 bytes. Along the way it was decided to add 2 spare bytes to the
record header, but regrettably the data section was not correspondingly
reduced in size so we end up with a record length of 130 bytes. This is
bad since it does not align with SD card flash sectors and results in
more erase/write flash cycles than necessary thus reducing the SD cards
life.
This update reduced the data section of the data manager to 124,
resulting in an optimal record length of 128 bytes.
In order to avoid the reuse of data previously written data in the old
format, which could result in catastrophic misinterpretation, the data
manager file is checked at startup. If it is found to be in the old
format, it is deleted and recreated with in the new record length. In
this case previously stored data is lost, but that is far safer than the
unpredictable result of using the old file.
- Add function to geo.c to determine if global position is inside fence
- Add navigator support/commands for maintaining fence coords.
- Add data manager module to support persistence fence storage. Can
store other data, but only used for fence at this time.
- Add unit tests for data manager
