From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Smith Subject: Re: Losing serial console boot output / sync_console Date: Sat, 2 Jul 2011 23:40:07 +0000 Message-ID: <20110702234007.GJ5935@bitfolk.com> References: <20110702200440.GG5935@bitfolk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Hi Keir, On Sun, Jul 03, 2011 at 12:14:32AM +0100, Keir Fraser wrote: > On 02/07/2011 21:04, "Andy Smith" wrote: > > About two months ago I sent this email to the Xen users lists > > regarding a problem I was having losing some of my serial console > > output on boot: > > > > http://lists.xensource.com/archives/html/xen-users/2011-04/msg00340.html > > If your serial line is very slow (I don't know why you're limited to 9600 > baud -- 115200 baud at least is usually possible) and there is a lot of boot > output then you can expect some of it to be discarded. We prefer to discard > data rather than spin-wait to send it as that can indeed cause other > time-critical services to be delayed too long. Fair enough. I'm not really concerned about things being slow during boot, more if sync_console would introduce strange latencies during normal operation even without excessive ongoing console output. Unfortunately I have no control over the terminal server configuration in this instance otherwise I'd certainly be using a higher baud rate. Having never had this problem with earlier versions of Xen or anything else I thought I better ask. > If you want to capture all Xen's boot output, the safest way is to increase > the serial transmit buffer size. Try adding serial_tx_buffer=64k to the Xen > command line. Thanks, I'll try that. Cheers, Andy