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Date: Fri, 3 Feb 2012 13:54:22 -0500
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Subject: Re: Slow stat() on noacl mounts due to x permission check
From: Earnie Boyd <earnie AT users DOT sourceforge DOT net>
To: cygwin AT cygwin DOT com
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On Fri, Feb 3, 2012 at 1:20 PM, Christian Franke
<Christian DOT Franke AT t-online DOT de> 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?
>

Yes.

> 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, ...
>

Yes it would break my use of this feature.

> Another more flexible solution would be a mount option to configure this.
> (xguess=0: no check; 1: some extensions only; 2: all files)
>

The default should be the existing behavior.

-- 
Earnie
-- https://sites.google.com/site/earnieboyd

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