/bin/grep is your friend.

fs/proc/proc_misc.c:498:

      seq_printf(p, "cpu%d %llu %llu %llu %llu %llu %llu %llu %llu\n",
         i,                                                           
         (unsigned long long)cputime64_to_clock_t(user),
         (unsigned long long)cputime64_to_clock_t(nice),
         (unsigned long long)cputime64_to_clock_t(system),
         (unsigned long long)cputime64_to_clock_t(idle),  
         (unsigned long long)cputime64_to_clock_t(iowait),
         (unsigned long long)cputime64_to_clock_t(irq),   
         (unsigned long long)cputime64_to_clock_t(softirq),
         (unsigned long long)cputime64_to_clock_t(steal)); 

kernel/sched.c:3113:

/*
 * Account for involuntary wait time.
 * @p: the process from which the cpu time has been stolen
 * @steal: the cpu time spent in involuntary wait
 */
void account_steal_time(struct task_struct *p, cputime_t steal)