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Message-ID: <276f0623-d08a-9048-cfe8-fb93a83394b3@cs.umass.edu>
Date: Mon, 22 Dec 2025 11:39:14 -0500
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Subject: Re: Why is stat slow?
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To: cygwin AT cygwin DOT com
Cc: Brian DOT Inglis AT SystematicSW DOT ab DOT ca
References: <74bdc787-9099-8e29-492a-588546b6eedb AT cs DOT umass DOT edu>
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 <510a193d-633c-ddf1-68a7-a61b9847cfa8 AT cs DOT umass DOT edu>
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In-Reply-To: <30e1a743-0e08-4f00-aafc-82fe7dd9078d@SystematicSW.ab.ca>
From: Eliot Moss via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Eliot Moss <moss AT cs DOT umass DOT edu>
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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 ?

Regards - Eliot

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