On Wed, 26 Jul 2023 20:16:16 +0800 Ze Gao <zegao2021@xxxxxxxxx> wrote: > @@ -231,41 +253,29 @@ TRACE_EVENT(sched_switch, > TP_STRUCT__entry( > __array( char, prev_comm, TASK_COMM_LEN ) > __field( pid_t, prev_pid ) > - __field( int, prev_prio ) > - __field( long, prev_state ) > + __field( short, prev_prio ) > + __field( int, prev_state ) > + __field( char, prev_state_char ) > __array( char, next_comm, TASK_COMM_LEN ) > __field( pid_t, next_pid ) > - __field( int, next_prio ) > + __field( short, next_prio ) > ), The above adds a bunch of holes. This needs to be reordered to condense the event, we don't want to increase it. libtraceevent will handle reordering. The above produces: struct { char prev_comm[16]; pid_t prev_pid; short prev_prio; <-- 2 character padding int prev_state; char prev_state_char; char next_comm[16]; <- 3 character padding pid_t next_pid; short next_prio; <- 2 char padding }; (all events are at least 4 byte aligned, and are multiple of 4 bytes in size, thus that last short of next_prio did nothing) The above is a total of 56 bytes (note, that is the same as the current sched_switch event size); What the above should be: TP_STRUCT__entry( __field( pid_t, prev_pid ) __field( pid_t, next_pid ) __field( short, prev_prio ) __field( short, next_prio ) __field( int, prev_state ) __array( char, prev_comm, TASK_COMM_LEN ) __array( char, next_comm, TASK_COMM_LEN ) __field( char, prev_state_char ) ), Which would be: struct { pid_t prev_pid; pid_t next_pid; short prev_prio; short next_prio; int prev_state; char prev_comm[16]; char next_comm[16]; char prev_stat_char; <-- 3 characters of padding } which would be 52 byte. Saving us 4 bytes per event. Which is a big deal! -- Steve