Win32 API FindFirstFile and FindNextFile performance vs command line

We have encountered an unexpected performance issue when traversing directories looking for files using a wildcard pattern.

We have 180 folders each containing 10,000 files. A command line search using dir <pattern> /s completes almost instantly (<0.25 second). However, from our application the same search takes between 3-4 seconds.

We initially tried using System.IO.DirectoryInfo.GetFiles() with SearchOption.AllDirectories and have now tried the Win32 API calls FindFirstFile() and FindNextF开发者_开发知识库ile().

Profiling our code using indicates that the vast majority of execution time is spent on these calls.

Our code is based on the following blog post:

http://codebetter.com/blogs/matthew.podwysocki/archive/2008/10/16/functional-net-fighting-friction-in-the-bcl-with-directory-getfiles.aspx

We found this to be slow so updated the GetFiles function to take a string search pattern rather than a predicate.

Can anyone shed any light on what might be wrong with our approach?

In my tests using FindFirstFileEx with FindExInfoBasic and FIND_FIRST_EX_LARGE_FETCH is much faster than the plain FindFirstFile.

Scanning 20 folders with ~300,000 files took 661 seconds with FindFirstFile and 11 seconds with FindFirstFileEx. Subsequent calls to the same folders took less than a second.

HANDLE h=FindFirstFileEx(search.c_str(), FindExInfoBasic, &data, FindExSearchNameMatch, NULL, FIND_FIRST_EX_LARGE_FETCH); 

You can try with an implementation of FindFirstFile and FindNextFile I once blogged about.

Try IShellFolder::EnumObjects with SHGetDataFromIDList/IShellFolder::GetAttributesOf.

Pro/Cons here.