通过perf record和perf report, 发现sys_nanosleep这个调用占比很高，达到6/7%.
sys_nanosleep是休眠的，为啥CPU占比这么高呢？难道是频繁调用这个函数导致的？

# Children      Self       Samples  Command       Shared Object                 Symbol
6.70%     0.19%          3022  decision  [kernel.kallsyms]             [k] sys_nanosleep
            |
             --6.51%--sys_nanosleep
                       |
                        --6.45%--hrtimer_nanosleep
                                  |
                                   --6.17%--do_nanosleep
                                             |
                                             |--4.34%--schedule
                                             |          |
                                             |           --4.12%--__schedule
                                             |                     |
                                             |                      --4.03%--finish_task_switch
                                             |                                |
                                             |                                 --3.99%--_raw_spin_unlock_irq
                                             |
                                              --1.38%--hrtimer_start_range_ns
                                                        |
                                                         --1.35%--_raw_spin_unlock_irqrestore
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FROM 107.182.184.*