| ANRdaemon is a daemon to help analyze ANR due to CPU starvation by logging system |
| activity when CPU usage is very high. The daemon uses debugfs underlying for |
| logging. Trace are configured ahead by setting different modules in /d/tracing. |
| Depending on the CPU usage level, the trace is turn on/off by writting to the |
| global control /d/trace/trace_on. The raw trace file is stored at |
| /d/tracing/trace. |
| |
| The daemon will be started at boot time and will be running with the following |
| settings: |
| $ anrd -t 9990 sched gfx am |
| This means tracing will be enabled above 99.90% CPU utilization and will trace |
| sched, gfx and am modules (See -h for more info). |
| |
| Use ANRdaemon_get_trace.sh [device serial] to dump and fetch the compressed trace file. |
| |
| The compressed trace file can be parsed using systrace: |
| $ systrace.py --from-file=<path to compressed trace file> |
| |
| Known issue: in the systrace output, anrdaemon will show up when the trace is |
| not running. This is because the daemon process turns off tracing when CPU usage |
| drops, the last entry it leaves in the raw trace file is the scheduler switched |
| from some other process to the daemon. Then sometime later (say 20 secs later), |
| when the CPU usage becomes high and the daemon process turn on tracing again, |
| the first entry in /d/tracing/trace logged by sched is switching away from the |
| daemon process to some other process. Due to this artifact, when the raw trace |
| file is parsed by systrace.py, the daemon process is shown as running for the |
| whole 20secs (because from systrace's view, the two 20 sec apart sched trace |
| entries regarding the daemon process indicates the daemon process ran continuously |
| for all 20sec). However, this will not affect the actual captured trace during |
| high CPU usage case. |
