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Message-ID: <5f1fb088-7f4b-4858-87b7-e1d89f5c7334@gmail.com>
Date: Mon, 22 Dec 2025 06:58:20 +0100
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Subject: Re: Why is stat slow?
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To: cygwin AT cygwin DOT com
References: <74bdc787-9099-8e29-492a-588546b6eedb AT cs DOT umass DOT edu>
In-Reply-To: <74bdc787-9099-8e29-492a-588546b6eedb@cs.umass.edu>
From: Marco Atzeri via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Marco Atzeri <marco DOT atzeri AT gmail DOT com>
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On 22/12/2025 06:15, Eliot Moss via Cygwin wrote:
> Dear Cygwin-ers --
> 
> 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
> 
> (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
> 
> A second run shortly after the first completes very quickly, indicating the
> presence of a cache :-) .
> 
> time stat <the files> on WSL2 gives:
> 
> real    0m2.208s
> user    0m0.026s
> sys     0m0.149s
> 
> This is after a reboot, so there is no caching available.  So, why is 
> Cygwin
> 60 times slower, even when WSL2 has the handicap of having to work 
> through the
> 9p adapter / COM surrogate?
> 
> Mostly I am curious, but this is also relevant because I rsync this file
> collection to offsite storage, and the stat time is about what it takes for
> rsync to start up - it needs to check file times and lengths.
> 
> This makes me wonder if there is something we can do to make this 
> better, by
> figuring out what WSL2 / 9p are doing ...
> 
> Best - Eliot Moss
> 

I do not notice a slow run.
The disk is an external 1T USB3 hard disk

$ time stat /dev/sdb1
   File: /dev/sdb1
   Size: 0               Blocks: 0          IO Block: 65536  block 
special file
Device: 8,17    Inode: 524305      Links: 1     Device type: 8,17
Access: (0666/brw-rw-rw-)  Uid: (197608/   Marco)   Gid: (197121/ NESSUNO)
Access: 2025-12-22 06:55:21.968106000 +0100
Modify: 2025-12-22 06:55:21.968106000 +0100
Change: 2025-12-22 06:55:21.968106000 +0100
  Birth: 2025-12-22 06:55:21.968106000 +0100

real    0m0.099s
user    0m0.030s
sys     0m0.000s

$ time stat /cygdrive/d
   File: /cygdrive/d
   Size: 0               Blocks: 8          IO Block: 65536  directory
Device: 54787,64366     Inode: 1407374883553285  Links: 1
Access: (0770/drwxrwx---)  Uid: (   18/  SYSTEM)   Gid: (   18/  SYSTEM)
Access: 2025-12-21 19:40:02.793348100 +0100
Modify: 2025-11-11 15:18:10.162456400 +0100
Change: 2025-11-11 15:18:10.162456400 +0100
  Birth: 2018-04-11 15:14:25.158842400 +0200

real    0m0.028s
user    0m0.015s
sys     0m0.000s

Regards
Marco

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