用ftrace抓取分析camera数据

ls /sys/kernel/tracing/events | grep -E
查看ftrace/tracepoint注册表

ls /sys/kernel/tracing/events/vb2
查看具体某个模块的tracepoint

cd /sys/kernel/tracing

echo 0 > tracing_on
echo > trace

echo 1 > tracing_on
echo 0 > tracing_on

cat trace > /data/local/tmp/vb2_trace.txt
adb pull /data/local/tmp/vb2_trace.txt

清空旧的trace，
只打开需要的tracepoint，
开始/停止记录，
导出trace

echo 1 > events/v4l2/v4l2_qbuf/enable
echo 1 > events/v4l2/v4l2_dqbuf/enable

echo 1 > events/v4l2/vb2_v4l2_qbuf/enable
echo 1 > events/v4l2/vb2_v4l2_buf_queue/enable
echo 1 > events/v4l2/vb2_v4l2_buf_done/enable
echo 1 > events/v4l2/vb2_v4l2_dqbuf/enable

echo 1 > events/syscalls/sys_enter_ioctl/enable
echo 1 > events/syscalls/sys_exit_ioctl/enable

不保存文件，直接看log
cd /sys/kernel/tracing
echo 0 > tracing_on
echo > trace
echo 1 > tracing_on
cat trace_pipe | grep -E "vb2_v4l2|v4l2_qbuf|v4l2_dqbuf"