extern size_t default_channel_subbuf_size;
extern size_t default_metadata_subbuf_size;
extern size_t default_ust_pid_channel_subbuf_size;
extern size_t default_channel_subbuf_size;
extern size_t default_metadata_subbuf_size;
extern size_t default_ust_pid_channel_subbuf_size;