From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH 1/2] xl: neuter vcpu-set --ignore-host. Date: Thu, 26 Sep 2013 21:52:16 -0400 Message-ID: <20130927015216.GD7952@konrad-lan.dumpdata.com> References: <1380141617-8981-1-git-send-email-konrad.wilk@oracle.com> <1380141617-8981-2-git-send-email-konrad.wilk@oracle.com> <1380186391.29483.18.camel@kazak.uk.xensource.com> <20130926152800.GD6538@konrad-lan.dumpdata.com> <1380210460.29483.134.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1380210460.29483.134.camel@kazak.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: George.Dunlap@eu.citrix.com, xen-devel@lists.xensource.com, Ian.Jackson@eu.citrix.com List-Id: xen-devel@lists.xenproject.org . snip.. > > I do get your frustration - why would a normal user want to shoot themselves > > in the foot with VCPU over-subscription? I have some faint clue - but I > > do to get a stream of requests from customers demanding it. > > And not a single one has explained to you why they want it? > > Or perhaps you could explain this faint clue of yours? I believe it is mostly driven by VMWare making statements that this is a OK scenario (see ESXi CPU considerations in http://www.vmware.com/pdf/Perf_Best_Practices_vSphere5.0.pdf) > > I'm not saying we can't make this change. I'm saying you haven't even > come close to giving a reasonable justification for it. I seem to > remember saying exactly the same thing last time we went around this > mulberry bush too. I learned two new idioms today - mulberry bush and tosh today :-) > > > And if they pay to > > shoot themselves in the foot - well, here is a cocked gun and let me point the > > gun at your foot and you can pull the trigger. > > They can use the override. Yes they can. I am was hoping we would allow a non override mode for those who really don't want any of these overrides. George suggested the "seatbelt" option and that looks to be a good compromise for me. > > > Lastly, now that the PV ticketlocks are in and they work for both PV and > > HVM I am curious how many people are going to start using it. > > Why would they? What possible benefit is there to doing this whether or > not PV ticketlocks are available? Because now one can run Linux guests without incuring huge latency waits due to spinlock contention. This makes it possible to actually compile a Linux kernel with massively overcommited scenarios.