From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Re: [Xen-changelog] fail domU creation if memory need couldn't be succeed after ballooning out dom0 Date: Thu, 18 Aug 2005 10:51:22 -0500 Message-ID: <4304AE7A.9060605@us.ibm.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: 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: Ian Pratt Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Ian Pratt wrote: >>In general, we should try to avoid using timeouts at all >>cost. If we do have to use a timeout, then we should make >>sure it's long enough that the timeout is never going to >>happen. It's surprisingly easy to have enough load on your >>system such you miss a 2 second timeout. >> >> > >Yep, in general I'm all for making timeouts long enough to be visible. > >However, this timeout is different: its something we expect may fail (as >opposed to an internal failure of the tools). > Is it really possible to fail? I just did: echo 42 > /proc/xen/balloon On domain-0 and the system crashed. It would be nice if it actually failed but currently the only thing this timeout will do is prevent us from working when we could have :-) How about when we fix the balloon driver, we have it write a node in the store that indicates whether the balloon has succeeded or failed and then the tools can simply set a watch and wait for something to happen? Regards, Anthony Liguori > We're asking domain 0 to >try and shrink itself. It may be unable to, in which case trying for a >few seconds and then failing the domain create seems like a good >approach. If domain 0 can't page enough stuff out after a second or two, >its unlikely to succeed without operator intervention (e.g. killing >something). > >2s is perhaps overly short, but I doubt going larger than 5s would >result in any greater chance of success, and would just anoy users. > >Ian > > >