What is sched_switch event in metadata?
sched_switch event defined in the metadata helps to identify if the thread is running or idle state.
sched_switch looks like this:
event {
name = "sched_switch";
id = 0;
stream_id = 0;
fields := struct {
integer { size = 8; align = 8; signed = 0; encoding = UTF8; base = 10;} _prev_comm[16];
integer { size = 32; align = 8; signed = 1; encoding = none; base = 10; } _prev_tid;
integer { size = 32; align = 8; signed = 1; encoding = none; base = 10; } _prev_prio;
integer { size = 64; align = 8; signed = 1; encoding = none; base = 10; } _prev_state;
integer { size = 8; align = 8; signed = 0; encoding = UTF8; base = 10; } _next_comm[16];
integer { size = 32; align = 8; signed = 1; encoding = none; base = 10; } _next_tid;
integer { size = 32; align = 8; signed = 1; encoding = none; base = 10; } _next_prio;
};
};A thread can have following types of state:
define TASK_RUNNING 0x0000
define TASK_INTERRUPTIBLE 0x0001
define TASK_UNINTERRUPTIBLE 0x0002
define TASK_PARKED 0x0040
define TASK_DEAD 0x0080
define TASK_WAKEKILL 0x0100
define TASK_WAKING 0x0200
define TASK_NOLOAD 0x0400
define TASK_NEW 0x0800
define TASK_STATE_MAX 0x1000
define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE)
define TASK_STOPPED (TASK_WAKEKILL | __TASK_STOPPED)
define TASK_TRACED (TASK_WAKEKILL | __TASK_TRACED)
define TASK_IDLE (TASK_UNINTERRUPTIBLE | TASK_NOLOAD)
define TASK_NORMAL (TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE)
define TASK_REPORT (TASK_RUNNING | TASK_INTERRUPTIBLE | \How to detect if the thread is idle or not?
If thread API returns 1 then it means it is idle thread.
( ( ( thread_id >> 24 ) & 0x7 ) == 1 )If above condtion returns 1 then it is idle thread. For idle thread _prev_tid of sched_switch value is 0.
References
Written on August 4, 2019