X-Recipient:	archive-cygwin AT delorie DOT com
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.4.1 sourceware.org BE99E3858C39
Authentication-Results:	sourceware.org;
	dmarc=none (p=none dis=none) header.from=cs.umass.edu
Authentication-Results:	sourceware.org; spf=pass smtp.mailfrom=cs.umass.edu
Subject:	Re: Curiosity about file access performance
To:	Adam Dinwoodie <adam AT dinwoodie DOT org>, cygwin <cygwin AT cygwin DOT com>
References:	<00895c47-8df9-1f17-baac-0b3560de9d1c AT cs DOT umass DOT edu>
	<CA+kUOamNpqUSnFOnnd0SdSZJj7uohG6LaDL4jz95cttbM8XDVQ AT mail DOT gmail DOT com>
From:	Eliot Moss <moss AT cs DOT umass DOT edu>
Message-ID:	<a68b69d2-9624-281e-a561-816bef366c2f@cs.umass.edu>
Date:	Fri, 29 Oct 2021 11:58:45 +0100
User-Agent:	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101
	Thunderbird/68.12.1
MIME-Version:	1.0
In-Reply-To:	<CA+kUOamNpqUSnFOnnd0SdSZJj7uohG6LaDL4jz95cttbM8XDVQ@mail.gmail.com>
X-Spam-Status:	No, score=-3.6 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS,
	NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS,
	TXREP autolearn=ham autolearn_force=no version=3.4.4
X-Spam-Checker-Version:	SpamAssassin 3.4.4 (2020-01-24) on
	server2.sourceware.org
X-BeenThere:	cygwin AT cygwin DOT com
X-Mailman-Version:	2.1.29
List-Id:	General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe:	<https://cygwin.com/mailman/options/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive:	<https://cygwin.com/pipermail/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe:	<https://cygwin.com/mailman/listinfo/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
Reply-To:	moss AT cs DOT umass DOT edu
Errors-To:	cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com
Sender:	"Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

On 10/29/2021 11:44 AM, Adam Dinwoodie wrote:

> AIUI it's a fundamental part of the trade-offs that NTFS makes:
> compared to common Linux file systems like ext4, NTFS is much slower
> at things like parsing directory structures (which is a necessary part
> of opening any given file). In the same way that native Windows
> programs tend to use threading implementations that work differently
> to fork(), native Windows applications will also often much prefer
> large monolithic data files, where native *nix applications are much
> more likely to have lots of small files. As a result, for things that
> require opening lots of files, WSL (at least if you're using the
> native WSL disk, which will be a *nix disk image stored in a file,
> rather than files under /mnt/c or similar) will likely be quicker than
> a similar operation through Cygwin, as Cygwin will always be affected
> by those NTFS overheads.

Ah, that's interesting.  The files in question, that seem to be opened
(and *maybe* read) faster are in the *nix hierarchy, while my book files
are all in Windows (/mnt/c on WSL1).  So the huge speedup reading those
makes sense.  The speedup processing the rest still doesn't quite make
sense, unless maybe WSL1's parsed-directory caching is more effective
than Cygwin's or something.  (I assume something like that is going on,
to reduce conversions of directories to *nix format.)

Regards - Eliot

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple

- Raw text -