Cygwin Filesystem Performance degradation 1.7.5 vs 1.7.7, and methods for improving performance

Corinna Vinschen corinna-cygwin@cygwin.com
Sun Sep 12 11:41:00 GMT 2010


On Sep 12 10:49, Yoni Londner wrote:
> Hi,
> 
> The caching-speed up is trivial:
> We store the the FileFullDirectoryInformation fields, and if any of
> them change - we re-read the file.
> 
> Its not (in practical life) possible to change a file without
> causing a modification on FileIndex/CreationTime/LastWriteTime/ChangeTime/EndOfFile/AllocationSize/FileAttributes/FileName/EaSize!
> 
> From the MSDN we see the info we can get on a
> FileFullDirectoryInformation request:

We're already using FileBothDirectoryInformation and
FileBothIdDirectoryInformation in readdir anyway.

However, isn't that kind of a chicken/egg situation?  If you want to
reuse the content of the FILE_BOTH{_ID}_DIRECTORY_INFORMATION structure
from a previous call to readdir, you would have to call the
corresponding NtQueryInformationFile call(s) to fetch the information
from the file for comparision purposes.  When you fetched it anyway,
there's no reason anymore to compare them, since you can use what
you just fetched.  Where's the advantage?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat



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