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Message-ID: <4F2C472C.1080403@t-online.de>
Date: Fri, 03 Feb 2012 21:44:28 +0100
From: Christian Franke <Christian DOT Franke AT t-online DOT de>
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To: cygwin AT cygwin DOT com
Subject: Re: Slow stat() on noacl mounts due to x permission check
References: <4F2C2589 DOT 2000907 AT t-online DOT de> <20120203191349 DOT GH30293 AT calimero DOT vinschen DOT de>
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Corinna Vinschen wrote:
> 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
>
>

Somehow I misunderstood the notexec option. Sorry for the noise.

Christian


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