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我正在使用 hwlat_detector 跟踪器来测量在 Linux 之外引起的系统延迟。

用于测量的机器是华硕 Zenbook ux331un。我确实使用 idle=poll 内核命令行参数禁用了处理器电源状态，禁用了超线程，禁用了涡轮增压。这是 hwlat 跟踪器的示例输出。

   <...>-4976  [002] d......  3258.677286: #81    inner/outer(us):   31/33    ts:1572267806.608681762
   <...>-4976  [003] dn.....  3276.085073: #82    inner/outer(us):   32/34    ts:1572267824.016656104
   <...>-4976  [000] d.L....  3277.113063: #83    inner/outer(us):   32/0     ts:1572267825.044656725
   <...>-4976  [003] dn.....  3280.181030: #84    inner/outer(us):   32/32    ts:1572267828.112657027
   <...>-4976  [000] dnL....  3281.205020: #85    inner/outer(us):   32/32    ts:1572267829.136657127
   <...>-4976  [002] dn.....  3283.252999: #86    inner/outer(us):  456/33    ts:1572267831.184659048
   <...>-4976  [003] dn.....  3284.276986: #87    inner/outer(us):   16/32    ts:1572267832.208656275
   <...>-4976  [000] dnL....  3285.300975: #88    inner/outer(us):   16/33    ts:1572267833.232656714
   <...>-4976  [002] dn.....  3287.348959: #89    inner/outer(us):   20/33    ts:1572267835.280662760
   <...>-4976  [003] dn.....  3288.372943: #90    inner/outer(us):   33/34    ts:1572267836.304657092
   <...>-4976  [000] dnL....  3289.396938: #91    inner/outer(us):   32/32    ts:1572267837.328663631
   <...>-4976  [002] dn.....  3291.444912: #92    inner/outer(us):   20/33    ts:1572267839.376659443

从输出中可以看出，发生了超过 400us 的延迟。我在 30us 范围内也有很多延迟。起初我认为延迟是由 SMI 引起的，所以我开始读取 MSR 寄存器 0x​​34，它计算自系统启动以来发生的 SMI 数量。测试运行时它不会增加。还有什么可能是这种延迟的原因？

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