如何使用 Process Control Monitor 計算 PCIe 插槽的運行時頻寬？

Question

我從事深度學習工作，並試圖找出 GPU 管道中的瓶頸。

我們在配備 4 個 NVIDIA Titan RTX 的 Intel Xeon 主機板上運行 Ubuntu。儘管 GPU 記憶體使用率約為 97%，但 nvidia-smi 測量的 GPU 利用率似乎相當低。

所以我想看看總線是否是瓶頸。

我已經下載了相變材料我正在運行它來監控 PCIe 3.0 x16 流量。

Processor Counter Monitor: PCIe Bandwidth Monitoring Utility 
 This utility measures PCIe bandwidth in real-time

 PCIe event definitions (each event counts as a transfer): 
   PCIe read events (PCI devices reading from memory - application writes to disk/network/PCIe device):
     PCIeRdCur* - PCIe read current transfer (full cache line)
         On Haswell Server PCIeRdCur counts both full/partial cache lines
     RFO*      - Demand Data RFO
     CRd*      - Demand Code Read
     DRd       - Demand Data Read
   PCIe write events (PCI devices writing to memory - application reads from disk/network/PCIe device):
     ItoM      - PCIe write full cache line
     RFO       - PCIe partial Write
   CPU MMIO events (CPU reading/writing to PCIe devices):
     PRd       - MMIO Read [Haswell Server only] (Partial Cache Line)
     WiL       - MMIO Write (Full/Partial)
...
Socket 0: 2 memory controllers detected with total number of 6 channels. 3 QPI ports detected. 2 M2M (mesh to memory) blocks detected.
Socket 1: 2 memory controllers detected with total number of 6 channels. 3 QPI ports detected. 2 M2M (mesh to memory) blocks detected.
Trying to use Linux perf events...
Successfully programmed on-core PMU using Linux perf
Link 3 is disabled
Link 3 is disabled
Socket 0
Max QPI link 0 speed: 23.3 GBytes/second (10.4 GT/second)
Max QPI link 1 speed: 23.3 GBytes/second (10.4 GT/second)
Socket 1
Max QPI link 0 speed: 23.3 GBytes/second (10.4 GT/second)
Max QPI link 1 speed: 23.3 GBytes/second (10.4 GT/second)

Detected Intel(R) Xeon(R) Gold 5122 CPU @ 3.60GHz "Intel(r) microarchitecture codename Skylake-SP" stepping 4 microcode level 0x200004d
Update every 1.0 seconds
delay_ms: 54
Skt | PCIeRdCur |  RFO  |  CRd  |  DRd  |  ItoM  |  PRd  |  WiL
 0      13 K        19 K     0       0      220 K    84     588  
 1       0        3024       0       0        0       0     264  
-----------------------------------------------------------------------
 *      13 K        22 K     0       0      220 K    84     852  

暫時忽略實際值。我有更大的價值觀。 :-)

如何使用 Process Control Monitor 計算 PCIe 插槽的運行時頻寬？

為什麼只列出兩個套接字？

Answer 1

從github OPCM：

插槽指的是 CPU 插槽，而不是 PCIe 插槽或裝置。您的系統有 2 個 CPU 插槽，對嗎？ --help 輸出描述了 -B 開關以輸出每個 CPU 插槽的頻寬（另請參閱此處有關部分操作的警告）。 pci-iio.x 是一個不同的實用程序，顯示每個 PCIe 設備的頻寬。