Where can see messages generated by blk_add_cgroup_trace_msg/blk_add_trace_msg?
 

I want to see the log messages generated by blk-throttle. It uses function like throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu", expires - jiffies, jiffies); The definition of throtl_log is

#define throtl_log(sq, fmt, args...) do { \
struct throtl_grp *__tg = sq_to_tg((sq)); \
struct throtl_data *__td = sq_to_td((sq)); \
\
(void)__td; \
if (likely(!blk_trace_note_message_enabled(__td->queue))) \
break; \
if ((__tg)) { \
blk_add_cgroup_trace_msg(__td->queue, \
tg_to_blkg(__tg)->blkcg, "throtl " fmt, ##args);\
} else { \
blk_add_trace_msg(__td->queue, "throtl " fmt, ##args); \
} \
} while (0)

But I don't know where/how I can see these messages.