Topic: Solution for slow CGI execution on Windows 10

[Miguel2016]

I'd like to call attention to a problem that affects everybody running any web server using CGI on any version of Windows 10.

I have recently started running servers on Windows 10 (32bit, 64bit, home, and Pro) using Apache for Windows, IIS, and other less known web servers for Windows.

One issue stood out - very slow CGI output from every server on any version of Windows 10. In particular this occurs when using large CGI scripts/binaries and large data passes from standard web forms.

In my case I created a C++ binary (as an EXE, 2mb in size) in the Cgi-Bin processing a standard web form passing over 4,000 variables. Before you think this is a lot, this identical arrangement using an XP server produced results in just 2 seconds. We expected upgrading to Windows 10 would match that speed.

Windows 10 took an average of 13 seconds to deliver CGI output compared to 2 seconds on XP. Obviously something was misconfigured on Windows 10.

It turns out that all versions of Windows 10 we tested suffer from an older Microsoft issue that required and still requires a simple, Microsoft endorsed registry hack to fix.

So here is the simple fix we used on our Windows servers to speed up CGI output. Search Google and you'll see this same fix being done 8 years ago.

Go to this registry location:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters

Right click Parameters and create a new DWORD named MaxBufferedSendBytes. Set the value to 65536. (We did this for 32bit because the binary was 32bit).

Reboot or restart your networking.

Upon rebooting our CGI on Windows 10 matched XP results, delivering output in 2 seconds.

As a mathematician I can't say I'm an expert in server or OS issues. It appears there are a number of other parameters that can be created and tweaked in this same registry area but none of them pertained to this slow CGI issue.

Miguel