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Date: Fri, 3 Feb 2012 20:13:49 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Slow stat() on noacl mounts due to x permission check
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On Feb  3 19:20, Christian Franke wrote:
> Cygwin stat() may be much slower on noacl mounts than on acl
> mounts.This is because on noacl mounts the x-permission bit is
> guessed by checking for "#!", ":" or "MZ" in the first bytes of the
> file. AFAIKS this is done for all files except *.exe, *.lnk and
> *.com.
> 
> A real world testcase with 20120201 snapshot on a (C++/Java
> development) tree with ~52000 files in ~12000 dirs:
> 
> .                            noacl  acl
> find -size ... (after boot)   518s  51s
> find -size ... (disk cached)   13s   8s
> find -name ... (disk cached)    3s   3s (does not need stat())
> 
> Is it really needed to do the header check for each file?
> 
> Would it break important use cases if the check is only done for
> files with typical script file extensions?
> For example: no extension, .sh, .csh, .pl, .py, ...
> 
> Another more flexible solution would be a mount option to configure this.
> (xguess=0: no check; 1: some extensions only; 2: all files)

We already have the exec/notexec/cygexec mount options, see
http://cygwin.com/cygwin-ug-net/using.html#mount-table


Corinna

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

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