Question

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

用于测量的机器是Asus Zenbook ux331un。我确实使用idle = poll kernel cmd-line参数禁用了处理器电源状态，禁用了超线程，禁用了turbo boost。这是hwlat跟踪程序的示例输出。

   <...>-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

从输出中可以看到，发生了超过400us的延迟。我也在30us范围内获得了很多延迟。起初，我认为延迟是由SMI引起的，因此我开始读取MSR寄存器0x34，该寄存器对自系统启动以来发生的SMI进行计数。测试运行时，它不会增加。造成这种延迟的原因还有哪些？

使用hwlat测得的意外高延迟峰值

0 个答案: