Slow stat() on noacl mounts due to x permission check
Christian Franke
Christian.Franke@t-online.de
Fri Feb 3 20:44:00 GMT 2012
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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