Question

我们测量了一些执行测试，我注意到CPU在内核模式下运行了很多时间。我想知道为什么会这样。

应用程序：它是Owin在IIS下监听的经典Azure云服务Web角色，而Owin本身只提供缓存在内存中的静态文件（因此应该只有一点性能损失，每个人都应该很快。内容通过await stream.CopyToAsync(response.Body)复制到输出流。

测试本身在加特林中看起来像这样：

val openLoginSet = exec(http("ROOT")
      .get("/")
      .headers(Headers105Test2.headers_0)
      .resources(
        http("MED: arrow-down-small.png").get(uriIconAssets + "/arrow-down-small.png").headers(Headers105Test2.headers_1),
        http("MED: arrow-up-small.png").get(uriIconAssets + "/arrow-up-small.png").headers(Headers105Test2.headers_1),
        http("MED: close-medium.png").get(uriIconAssets + "/close-medium.png").headers(Headers105Test2.headers_1),
        http("MED: decline-medium.png").get(uriIconAssets + "/decline-medium.png").headers(Headers105Test2.headers_1),
        http("MED: help-medium.png").get(uriIconAssets + "/help-medium.png").headers(Headers105Test2.headers_1),
        http("MED: submit-medium.png").get(uriIconAssets + "/submit-medium.png").headers(Headers105Test2.headers_1),
        http("MED: delete-medium.png").get(uriIconAssets + "/delete-medium.png").headers(Headers105Test2.headers_1),
        http("MED: en-us.js").get("/en-us.js").headers(Headers105Test2.headers_8),
        http("MED: cloud_logo_big.png").get("/assets/cloud_logo_big.png").headers(Headers105Test2.headers_1),
        http("MED: favicon.ico").get("/favicon.ico").headers(Headers105Test2.headers_0))

val httpProtocol = http
  .baseURL("https://myurl.com")
  .inferHtmlResources()

val openLoginSenario = scenario("OpenOnly").exec(repeat(400, "n") {
    exec(openLoginSet).pause(3,6)
})

setUp(openLoginSenario.inject(rampUsers(150) over (3 minutes)))
  .protocols(httpProtocol)
  .maxDuration(3 minutes)

（我将测试缩短为运行3分钟，只是为了抓住数据显示在这里）有3台计算机运行这个加特林测试，每个计算机最多150个并发线程，总共450个线程。

我看到内核中运行的代码很多，W3wp进程不占用大部分CPU：

测试刚启动时捕获的CPU（添加新线程时cpu正在上升）：

测试几乎在结束前捕获CPU：

内核模式看起来很糟糕，我不确定是什么原因造成的。应该几乎没有涉及锁。当阅读其他可能导致高内核模式的内容时，我发现DPC可能会导致它。所以我也捕获了一些DPC数据，但我不确定什么是正常的，什么不是。无论如何，具有DPC最大时间的图表也包含在sshot中。

vmbus.sys占用了所有DPC的最重要时间。这意味着Azure实例不是任何裸机（并不令人惊讶），并且该实例与其他实例共享它的计算能力。据我了解，vmbus.sys负责例如网卡本身和托管的HyperV实例。可能在HyperV中运行是导致性能低下的主要原因吗？

我想知道在哪里查看，以及如何在我的情况下找出导致内核模式的原因。

更多数据：

测试开始时的部分DPC数据（在30秒内拍摄）：

Total = 17887 for module vmbus.sys
Elapsed Time, >        0 usecs AND <=        1 usecs,    137, or   0.77%
Elapsed Time, >        1 usecs AND <=        2 usecs,   2148, or  12.01%
Elapsed Time, >        2 usecs AND <=        4 usecs,   3941, or  22.03%
Elapsed Time, >        4 usecs AND <=        8 usecs,   2291, or  12.81%
Elapsed Time, >        8 usecs AND <=       16 usecs,   5182, or  28.97%
Elapsed Time, >       16 usecs AND <=       32 usecs,   3305, or  18.48%
Elapsed Time, >       32 usecs AND <=       64 usecs,    786, or   4.39%
Elapsed Time, >       64 usecs AND <=      128 usecs,     85, or   0.48%
Elapsed Time, >      128 usecs AND <=      256 usecs,      6, or   0.03%
Elapsed Time, >      256 usecs AND <=      512 usecs,      1, or   0.01%
Elapsed Time, >      512 usecs AND <=     1024 usecs,      2, or   0.01%
Elapsed Time, >     1024 usecs AND <=     2048 usecs,      0, or   0.00%
Elapsed Time, >     2048 usecs AND <=     4096 usecs,      1, or   0.01%
Elapsed Time, >     4096 usecs AND <=     8192 usecs,      2, or   0.01%
Total,                                                 17887

测试结束时DPC数据的一部分（在30秒内拍摄）：

Total = 141796 for module vmbus.sys
Elapsed Time, >        0 usecs AND <=        1 usecs,   7703, or   5.43%
Elapsed Time, >        1 usecs AND <=        2 usecs,  21075, or  14.86%
Elapsed Time, >        2 usecs AND <=        4 usecs,  17301, or  12.20%
Elapsed Time, >        4 usecs AND <=        8 usecs,  38988, or  27.50%
Elapsed Time, >        8 usecs AND <=       16 usecs,  32028, or  22.59%
Elapsed Time, >       16 usecs AND <=       32 usecs,  11861, or   8.36%
Elapsed Time, >       32 usecs AND <=       64 usecs,   7034, or   4.96%
Elapsed Time, >       64 usecs AND <=      128 usecs,   5038, or   3.55%
Elapsed Time, >      128 usecs AND <=      256 usecs,    606, or   0.43%
Elapsed Time, >      256 usecs AND <=      512 usecs,     53, or   0.04%
Elapsed Time, >      512 usecs AND <=     1024 usecs,     26, or   0.02%
Elapsed Time, >     1024 usecs AND <=     2048 usecs,     11, or   0.01%
Elapsed Time, >     2048 usecs AND <=     4096 usecs,     10, or   0.01%
Elapsed Time, >     4096 usecs AND <=     8192 usecs,     53, or   0.04%
Elapsed Time, >     8192 usecs AND <=    16384 usecs,      3, or   0.00%
Elapsed Time, >    16384 usecs AND <=    32768 usecs,      1, or   0.00%
Elapsed Time, >    32768 usecs AND <=    65536 usecs,      5, or   0.00%
Total,                                                141796

％DPC从测试开始到结束的时间