From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail108.syd.optusnet.com.au (mail108.syd.optusnet.com.au [211.29.132.59]) by sourceware.org (Postfix) with ESMTP id 4D61D3857412 for ; Thu, 10 Jun 2021 02:23:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4D61D3857412 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=optusnet.com.au Authentication-Results: sourceware.org; spf=fail smtp.mailfrom=dimstar.local.net Received: from dimstar.local.net (n49-192-76-174.sun3.vic.optusnet.com.au [49.192.76.174]) by mail108.syd.optusnet.com.au (Postfix) with SMTP id ACAB11B342C for ; Thu, 10 Jun 2021 12:23:04 +1000 (AEST) Received: (qmail 29407 invoked by uid 501); 10 Jun 2021 02:23:03 -0000 Date: Thu, 10 Jun 2021 12:23:03 +1000 From: Duncan Roe To: cygwin@cygwin.com Subject: Re: odd prob for cygwin 'dd' from a character device on network disk Message-ID: <20210610022303.GA14223@dimstar.local.net> Mail-Followup-To: cygwin@cygwin.com References: <60C168AF.4070400@tlinx.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60C168AF.4070400@tlinx.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=F8MpiZpN c=1 sm=1 tr=0 a=2x+9a05Zy+c+NO1c5nU3Ew==:117 a=2x+9a05Zy+c+NO1c5nU3Ew==:17 a=kj9zAlcOel0A:10 a=r6YtysWOX24A:10 a=RSmzAf-M6YYA:10 a=e-ICQenMb20CKPRKd80A:9 a=CjuIK1q_8ugA:10 X-Spam-Status: No, score=-4.0 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, RCVD_IN_DNSWL_LOW, SPF_FAIL, SPF_HELO_PASS, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: cygwin@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Jun 2021 02:23:10 -0000 On Wed, Jun 09, 2021 at 06:19:43PM -0700, L A Walsh wrote: > I've been using a character device on linux in my > home directory named 'zero' that is a copy of the > 'zero' device in /dev: > crwxrwxrw- 1 1, 5 Jun 15 2015 zero > > to do read benchmarks using 'dd' (and write benchmarks > using a file named 'null' thats a copy of /dev/null). > > I run it "occasionally", but not on a regular basis, since > it stays a bit boring. Nevertheless, ballpark numbers > consistent with historical norms verify correct network > function (separate from read/write files). Read/write speeds > at last check a few weeks ago were typical with > reads at 700MB/s and writes at about 300MB/s. > > A few hours ago I tried it again due to some strange network > probs where I seemed to be getting file xfer speeds as low > as 200K/s. > > I tried the bench script, and its half broken now -- because > I can no longer get anything back from the zero device > on my server via the network. Locally, I can do 'dd' from > /dev/zero (or the zero file) and it takes a few seconds and > gave about 800MB/s. So seemed to have been working fine, > but remotely -- still nada... reads 0 bytes from /dev/zero > and about 300MB/s write speed. > > Can anyone think of anything that might have changed in > cygwin such that it would know the remote device is a > "/dev/zero". Wondered if the 'dd' prog might have changed, > but just realize it did same with 'cat' as well. > > Anyway -- I'm a bit stumped as to possible causes... > The writing to a remote /dev/null part is still working, > so not sure why one would change and not the other. > > If anyone can think of anything, please let me know -- I'm > also gonna ping the samba list and maybe my distro list > > Thanks! > -linda > nfs / nodev?