X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org F1C803858C55
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1712063879;
	bh=y8S7kpXb9KKQEwDF2ycWrsbetI79UXj/vdf5/dKBtIg=;
	h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	 From;
	b=wr2p8j2zq0buuq/gMZkyOIHCPHESQ1D4FyASN0X4MSMJbSXg2KxtKocM+Hmc2O+Jm
	 UQj2STe4S085MQXnCsDV/lXgOmdJ/jbdDBPfVZZYzRoBDVct/9Y1y3Mb7bjVXUQga2
	 tT3a6OjwCmS4PprewsLzP41eHgRg5+tFroUZh9os=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5C56F3858424
Date: Tue, 2 Apr 2024 15:16:37 +0200
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin&Win32 file prefetch, block sizes?
Message-ID: <ZgwFNde2z804koS_@calimero.vinschen.de>
Mail-Followup-To: cygwin AT cygwin DOT com
References: <CANH4o6Mxai4_C=d1P93Prrimb8_H=trTwm-Eg+WBwpomN3tNJw AT mail DOT gmail DOT com>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <CANH4o6Mxai4_C=d1P93Prrimb8_H=trTwm-Eg+WBwpomN3tNJw@mail.gmail.com>
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
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>
From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
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 Apr  2 02:04, Martin Wege via Cygwin wrote:
> Hello,
> 
> Is there any document which describes how Cygwin and Win32 file
> prefetch and readahead work, and which sizes are used (e.g. always
> read one full page even if only 16 bytes are requested?)?

I'm not aware of any docs, but again, keep in mind that Cygwin is a
usersapce DLL. We basically do what Windows does for low-level file
access.

> Quick /usr/bin/stat /etc/profile returns "IO Block: 65536". Does that
> mean the file's block size is really 64k? Is this info per filesystem,
> or hardcoded in Cygwin?

Hardcoded in Cygwin since 2017, based on a discussion in terms of
file access performance, especially when using stdio.h functions:

  https://cygwin.com/cgit/newlib-cygwin/commit/?id=7bef7db5ccd9c

Corinna

-- 
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