From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.11] helo=sc8-sf-mx1.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1BEVIu-00017I-8B for user-mode-linux-devel@lists.sourceforge.net; Fri, 16 Apr 2004 08:30:56 -0700 Received: from main.gmane.org ([80.91.224.249]) by sc8-sf-mx1.sourceforge.net with esmtp (Exim 4.30) id 1BEVIs-0002DE-BY for user-mode-linux-devel@lists.sourceforge.net; Fri, 16 Apr 2004 08:30:54 -0700 Received: from root by main.gmane.org with local (Exim 3.35 #1 (Debian)) id 1BEVIp-0008Kz-00 for ; Fri, 16 Apr 2004 17:30:51 +0200 Received: from office.bytemark.co.uk ([82.133.96.198]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 16 Apr 2004 17:30:51 +0200 Received: from matthew by office.bytemark.co.uk with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 16 Apr 2004 17:30:51 +0200 From: Matthew Bloch Message-ID: References: <185d01c41e23$5996cc00$2000000a@schlepptopp> <189201c41e30$d434cc70$2000000a@schlepptopp> <200404091626.i39GQqsf002414@ccure.user-mode-linux.org> <20040410140840.GB5782@ccure.user-mode-linux.org> <4077FDF9.7070707@upb.de> <20040410170707.GA6492@ccure.user-mode-linux.org> <224701c42280$f110e0f0$2000000a@schlepptopp> <000801c422e1$783f8030$1400a8c0@DAVIDVAIO> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit In-Reply-To: <000801c422e1$783f8030$1400a8c0@DAVIDVAIO> Subject: [uml-devel] Re: [uml-user] Network lags Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Fri, 16 Apr 2004 16:12:30 +0100 To: user-mode-linux-devel@lists.sourceforge.net Cc: user-mode-linux-user@lists.sourceforge.net David Cannings wrote: >>>Anyone else who's running lots of UMLs with interactive sessions may have >>>noticed the following symptoms which this patch cures: >>> >>> * irregular ping times to UMLs-- huge delay for the first ping, a few >>> normal, a couple of long delays etc.; > > The huge delay is often related to ARP, a fundamental part of 802.3/true > ethernet. Indeed, but when logging back on to an ssh session etc. it's very irritating for customers to find their machine takes seconds to "wake up" while the 2.4 kernel swaps stuff back in. [snip] > The problem with "just activating that option" is that many people will do > it blindly, unaware of the serious implications it could have to their host. > Whilst mlocking an area of memory may not affect you now, or in the next ten > minutes, it could cause trouble in three weeks when you start doing > something on the host that is memory intensive. In the last three years of > running a remote server I have only had to turn up on site to fix it twice. > Both were very silly things, one that I'd "just activated" to see what it > would do. It cost me a rather expensive journey half way across the country > to fix. Since writing that post back in October, we've deployed the mlock patch across two rackfuls of hosts, and we've never had a host kernel "just crash" (well we have, but that was down to something else ): longest uptime on one group of our hosts is 100 days. Yes it was experimental but we did a bit of testing first. From this experience; I would disagree that using lots of mlocked memory inherently destabilises the machine. I'm sure it *can* but this goes for a lot of things. [snip] > The idea behind UML is to create a separate environment from the host, > constructing a UML kernel that can interfere so badly with the host is the > total opposite. It's very easy for a UML kernel to trash the host, and I'm not sure anyone knows what "the idea behind UML" is :-) I can see Jeff's point about the mlock patch despite the fact that it solved a major problem for us with deploying UML in a hosting environment. Jeff's proposed new memory management features will give us more flexibility than my simple on/off mlock patch, and allows him to wash his hands of these grubby management decisions. cheerio, -- Matthew Bloch Bytemark Hosting http://www.bytemark-hosting.co.uk/ phone UK: 0845 004 3 004 US: 1-877 BYTEMAR Dedicated Linux hosts from 15ukp ($26) per month ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel