使用DXIFRShim性能测量使用了大量CPU

你好，
我一直在使用DXIFRShim样本进行一些性能测量，我已经开始注意到垫片层似乎使用了大量的CPU。
一些背景优先。
这是我正在使用的：
系统规格
GRID K520
4 GB RAM
VM中的Intel Xeon E3-2603 v3。
拥有2个CPU内核@ 1.6 GHz
软件
Capture SDK 5.0
Windows 8.1 64位
游戏是虚幻引擎的第一人称射击游戏模板（版本4.13）
DXIFRShim样本
CPU测量以一种简单的方式完成：我使用任务管理器查看游戏过程的百分比。
这是我注意到的：
当游戏在没有垫片层（即原始.dll文件）的情况下运行时，CPU利用率％约为22％。
当游戏使用DXIFRShim运行时，CPU利用率％约为40％。
这几乎翻了一番。
考虑到Capture SDK的重点是要做更快的GPU编码而不是CPU编码，CPU利用率％几乎翻倍是相当奇怪的。
我继续发表评论来自NvIFREncoder.cpp的大量代码，并发现这一行是罪犯：
NVIFRRESULT nr = pIFR-> NvIFRSetUpHWEncoder（＆amp; params）;
留下这一行并在其后面注释掉所有内容（包括实际编码和写入视频文件）仍会导致高CPU利用率％。
在此行注释掉的那一刻，CPU利用率回到百分比，就像垫片层不在那里一样。
我发现这很奇怪，因为人们会期望大部分工作都在编码循环中，这将是包含“NvIFRTransferRenderTargetToHWEncoder（）;”的“while”循环。
我无法查看NvIFRSetUpHWEncoder本身的实现，所以我想知道：为什么CPU使用率相当高？
有没有办法避免或减少它仍然能够进行GPU编码？
谢谢！



以下为原文

Hello,

I have been doing some performance measurements using the DXIFRShim sample, and I have started to notice that the shim layer seems to use a huge amount of CPU.

Some background first. Here is what I am using:

• System Specs
  
  • GRID K520
  • 4 GB RAM
  • Intel Xeon E3-2603 v3 in a VM. Has 2 CPU cores @1.6 GHz
    
• Software
  
  • Capture SDK 5.0
  • Windows 8.1 64-bit
  • Game is Unreal Engine's first person shooter template (version 4.13)
  • DXIFRShim sample
    
  
  

The CPU measurement is done in a simple way: I use task manager to look at the percentages given for the game process.

Here is what I noticed:

• When the game is running without the shim layer (i.e. original .dll files), the CPU utilization % is about 22%.
• When the game is running with DXIFRShim, the CPU utilization % is about 40%. This is almost double.
  

Considering that the whole point of the Capture SDK is to do much faster GPU encoding instead of CPU encoding, having the CPU utilization % to almost double is rather strange.

I went ahead to comment out huge chunks of code from NvIFREncoder.cpp, and found out that this line is the offender:
NVIFRRESULT nr = pIFR->NvIFRSetUpHWEncoder(¶ms);
Leaving this line in and commenting out everything after it (which includes the actual encoding and writing to video file) still results in high CPU utilization %. The moment this line is commented out, the CPU utilization goes back to the percentages as if the shim layer was not there. I found this rather strange since one would expect the majority of the work to be in the encoding loop, which would be the "while" loop containing "NvIFRTransferRenderTargetToHWEncoder();".

I am not able to look at the implementation of NvIFRSetUpHWEncoder itself, so I am wondering: why is the CPU usage rather high? Is there a way to avoid or reduce it while still being able to do GPU encoding?

Thanks!