|
| 1 | +# mbed-memory-status |
| 2 | + |
| 3 | +## Purpose |
| 4 | + |
| 5 | +Print thread stack, ISR stack, and global heap locations, sizes, and utilization at runtime when using mbed OS. Useful for tracking down total runtime memory usage and stack overflows. |
| 6 | + |
| 7 | +It will print debug information to the serial port, or use SEGGER Real Time Transfer (RTT), or use the Serial Wire Output (SWO) capabilities in supported ARM Cortex chips. |
| 8 | + |
| 9 | +Does *not* use printf(). It *will* automatically initialize the default serial port to 115200 8N1 using the low-level mbed `serial_api.h` if no other instantiation has occurred. |
| 10 | + |
| 11 | +The code has now been fixed to detect whether it is running on the CMSIS-RTOS 1 or CMSIS-RTOS 2 API and will adjust its low-level API calls accordingly. |
| 12 | + |
| 13 | +## Example |
| 14 | + |
| 15 | +```c |
| 16 | +#include "mbed_memory_status.h" |
| 17 | + |
| 18 | +int main() |
| 19 | +{ |
| 20 | + print_all_thread_info(); |
| 21 | + print_heap_and_isr_stack_info(); |
| 22 | +} |
| 23 | +``` |
| 24 | + |
| 25 | +## Building |
| 26 | + |
| 27 | +When building the code, make sure to pass the `MBED_STACK_STATS_ENABLED` compiler macro as follows, otherwise mbed will eliminate the stack canary code: |
| 28 | + |
| 29 | +``` |
| 30 | +mbed compile -D MBED_STACK_STATS_ENABLED=1 |
| 31 | +``` |
| 32 | + |
| 33 | +This value can also be added permanently to the `mbed_app.json` macros. |
| 34 | + |
| 35 | +## Output |
| 36 | + |
| 37 | +Using ARM RTX RTOS on up to mbed 5.4.7, this will print something like: |
| 38 | + |
| 39 | +``` |
| 40 | + stack ( start: 20005100 end: 20005420 size: 00000320 used: 00000070 ) thread ( id: 2000542C entry: 00020D91 ) |
| 41 | + stack ( start: 20003D1C end: 2000451C size: 00000800 used: 00000254 ) thread ( id: 2000546C entry: 000201E1 ) |
| 42 | + stack ( start: 20004E58 end: 20005058 size: 00000200 used: 00000050 ) thread ( id: 20005644 entry: 0002022D ) |
| 43 | + heap ( start: 200056E8 end: 20007800 size: 00002118 used: 00000398 ) alloc ( ok: 00000006 fail: 00000000 ) |
| 44 | +isr_stack ( start: 20007800 end: 20008000 size: 00000800 used: 000002B0 ) |
| 45 | +``` |
| 46 | + |
| 47 | +Using CMSIS-RTOS 2 from mbed 5.5 and higher, we gain access to thread names, so this will print something like: |
| 48 | + |
| 49 | +``` |
| 50 | + stack ( start: 20004628 end: 20005628 size: 00001000 used: 000000F8 ) thread ( id: 200045D8 entry: 0001CEBD name: main_thread ) |
| 51 | + stack ( start: 200040A0 end: 200042A0 size: 00000200 used: 00000100 ) thread ( id: 20003D58 entry: 0001D019 name: unknown ) |
| 52 | + stack ( start: 20003DA0 end: 200040A0 size: 00000300 used: 00000068 ) thread ( id: 20003D10 entry: 0001F1BD name: unknown ) |
| 53 | + heap ( start: 20005738 end: 2000FC00 size: 0000A4C8 used: 00000000 ) alloc ( ok: 00000000 fail: 00000000 ) |
| 54 | +isr_stack ( start: 2000FC00 end: 20010000 size: 00000400 ) |
| 55 | +``` |
| 56 | + |
| 57 | +## Use |
| 58 | + |
| 59 | +Add to your program: |
| 60 | + |
| 61 | +``` |
| 62 | +mbed add https://github.com/nuket/mbed-memory-status.git mbed-memory-status |
| 63 | +``` |
| 64 | + |
| 65 | +To enable the ISR stack usage tracking, the following assembly code needs to be added to your chip's specific `startup_[your chip].S` file: |
| 66 | + |
| 67 | +```asm |
| 68 | +#if DEBUG_ISR_STACK_USAGE |
| 69 | + LDR R0, =fill_isr_stack_with_canary |
| 70 | + BLX R0 |
| 71 | +#endif |
| 72 | +``` |
| 73 | + |
| 74 | +See the `startup_example.S.txt` file for what this looks like (the file is a modified copy of `startup_NRF51822.S`). |
| 75 | + |
| 76 | +Then define this in `mbed_memory_status.c`, or via the `mbed_app.json` macros, or via the command line: |
| 77 | + |
| 78 | +```c |
| 79 | +#define DEBUG_ISR_STACK_USAGE 1 |
| 80 | +``` |
| 81 | +
|
| 82 | +## Outputs |
| 83 | +
|
| 84 | +With `#define OUTPUT_SERIAL 1`: |
| 85 | +
|
| 86 | + |
| 87 | +
|
| 88 | +With `#define OUTPUT_RTT 1`: |
| 89 | +
|
| 90 | + |
| 91 | +
|
| 92 | +With `#define OUTPUT_SWO 1` (and `-D ENABLE_SWO` on an nRF52 Development Kit): |
| 93 | +
|
| 94 | + |
| 95 | +
|
| 96 | +And, having all of them active together works too! |
| 97 | +
|
| 98 | + |
| 99 | +
|
| 100 | +## Supports |
| 101 | +
|
| 102 | +[mbed OS](https://github.com/ARMmbed/mbed-os/) 5.2.0 - 5.9.5 (and up to [b53a9ea](https://github.com/ARMmbed/mbed-os/commit/b53a9ea4c02fd67cb0cc94d08361e8815585b7bf)) |
| 103 | +
|
| 104 | +## Gotchas |
| 105 | +
|
| 106 | +On mbed 5.5 and up, there may be a Heisenbug when calling print_thread_info() inside of osKernelLock()! |
| 107 | +
|
| 108 | +This error sometimes appears on the serial console shortly after chip startup, but not always: |
| 109 | +`mbed assertation failed: os_timer->get_tick() == svcRtxKernelGetTickCount(), file: .\mbed-os\rtos\TARGET_CORTEX\mbed_rtx_idle.c` |
| 110 | +
|
| 111 | +The RTOS seems to be asserting an idle constraint violation due to the slowness of sending data through the serial port, but it does not happen consistently. |
| 112 | +
|
| 113 | +Resetting or power-cycling the chip may solve this problem. |
| 114 | +
|
| 115 | +## Why This Exists |
| 116 | +
|
| 117 | +This code exists because of a stupid amount of bug-hunting: |
| 118 | +
|
| 119 | +> https://vilimpoc.org/blog/2017/02/01/stack-heap-and-thread-crash-hunting-in-mbed-os/ |
| 120 | +> https://vilimpoc.org/blog/2017/02/04/isr-stack-usage-on-mbed/ |
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