Why is stat slow?

[Brian.Inglis@SystematicSW.ab.ca]

On 2025-12-22 09:39, Eliot Moss wrote:
> On 12/22/2025 11:28 AM, Brian Inglis via Cygwin wrote:
>> 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.
> 
> Interesting; so the suggested /etc/fstab line would be this?
> 
> d: /\d ntfs binary,posix=0,user 0 0
> 
> How do I type a path, then, e.g., now I might have /d/foo ... ?
> Would I have to type /\d/foo ?

No change to fstab - just be wary of typing /? in a Cygwin shell command line.
I once tried mapping my cygdrives under root / so every cmd help /? expanded to 
/c /d /f /g and I used it and forgot often enough to be annoying so reverted to 
/mnt.

-- 
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