offcpu-cost.stp

#! /usr/bin/env stap

# usage:
#   stap tools/offcpu-cost.stp -x ${pid} -D MAXSKIPPED=1000000 -t -v -w -T 1

global MAX_PROBE_NUM = 10000 # max context-switch number
global cur_probe_num = 0

global begin_sleep_time
global delta

probe kernel.function("finish_task_switch@kernel/sched/core.c") {
#target_pid = strtol(@1, 10)
    if (pid() != target()) next
    if (cur_probe_num >= MAX_PROBE_NUM) next

    begin_sleep_time[$prev->pid] = gettimeofday_us()

    if (!begin_sleep_time[tid()])
        next
    elapse = gettimeofday_us() - begin_sleep_time[tid()]
    stack = sprint_ubacktrace()
    delta[stack] += elapse
    begin_sleep_time[tid()] = 0
    cur_probe_num += 1
}

probe end {
    n = 0
    foreach (stack in delta-) {
        if (n < 10) {
            printf("%d\n%s\n===============\n\n", delta[stack], stack)
        }
        n += 1
    }
}