Why is stat slow?

[Brian.Inglis@SystematicSW.ab.ca]

On 2025-12-22 08:35, Eliot Moss via Cygwin wrote:
> On 12/22/2025 10:07 AM, Christian Franke via Cygwin wrote:
>> Eliot Moss via Cygwin wrote:
>>> I'm sure this has been asked before, more than once, but I am again wondering
>>> what, specifically, makes stat (the program, but presumably also the syscall)
>>> substantially slower on Cygwin compared to stat on WSL2.  I am talking about
>>> an external HDD (not solid state) on my D: drive.  It shows under WSL 2 as
>>> /mnt/d like this (output of mount):
>>>
>>> D:\ on /mnt/d type 9p (rw,noatime,aname=drvfs;path=D: 
>>> \;uid=0;gid=0;symlinkroot=/ 
>>> mnt/,cache=5,access=client,msize=65536,trans=fd,rfd=5,wfd=5)
>>>
>>> On Cygwin it shows up like this (yes, mount shows two lines):
>>>
>>> D: on /cygdrive/d type ntfs (binary,notexec,posix=0,user)
>>> D: on /cygdrive/d type ntfs (binary,noacl,posix=0,user,noumount,auto)
>>>
>>> My /etc/fstab lines are:
>>>
>>> none /cygdrive cygdrive binary,noacl,posix=0,user 0 0
>>> d: /cygdrive/d ntfs binary,posix=0,user,auto,notexec 0 0
>>
>> In the past, Cygwin did not support individual options for some /cygdrive/X. 
>> If this is still the case, "noacl" without "notexec" is effective for / 
>> cygdrive/d. Then Cygwin reads the header of each file to check for a possible 
>> "x" permission.

>>> (Presumably this has something to do with two mounts showing ...)
>>>
>>> On D; I have a folder with hundreds of 2Gb files (they are backups, split into
>>> 2Gb portions).  On Cygwin
>>>
>>> time stat <the files> gives
>>>
>>> real    2m12.425s
>>> user    0m0.249s
>>> sys     0m1.312s

>> This would explain this long duration.
>>
>> Quick test:
>>
>> $ echo '#!/bin/sh' > /cygdrive/d/script.tmp
>> $ ls -l /cygdrive/d/script.tmp
>> -rwxr-xr-x .... <== notexec unset
>> -rw-r--r-- .... <== notexec set

> Aha!  I changed my /etc/fstab to be like this:
> 
> none /cygdrive cygdrive binary,noacl,posix=0,user 0 0
> d: /d ntfs binary,posix=0,user 0 0
> 
> D: is still available via explicit /cygdrive/d, but that would be without the
> noacl option.  Using /d now the previously slow stat completes in a few
> seconds, reasonable for going over what is now 2000 files.  My memory of
> exactly why is dim, but the noacl seems important for my C: drive.  Using the
> ACLs on D: to determine executability seems good.

Mapping drives to /? causes an issue if you ever want to get help from any 
non-Cygwin Windows console program that uses Windows help conventions /? -> /d: 
I believe using /\? avoids that.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retrancher  but when there is no more to cut
                                 -- Antoine de Saint-Exupéry