From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: x86/dom0: limit dom0_max_vcpus value Date: Mon, 12 Mar 2012 16:32:39 +0000 Message-ID: <4F5E2527.9030605@citrix.com> References: <4F5E1CA5.1060103@citrix.com> <4F5E2E750200007800077C1B@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F5E2E750200007800077C1B@nat28.tlf.novell.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: Jan Beulich Cc: "Keir (Xen.org)" , xen-devel List-Id: xen-devel@lists.xenproject.org On 12/03/12 16:12, Jan Beulich wrote: >>>> On 12.03.12 at 16:56, Andrew Cooper wrote: >> This caused particularly poor performance when booting a server in >> uniprocessor mode for debugging reasons, and had 4 dom0 vcpus competing >> for 1pcpus worth of time. > NAK. This was intentionally removed in an earlier c/s (and I'm in fact > making use of this for certain types of stress tests). No-one forces > you or anyone else to boot with dom0_max_vcpus=4 when there's > just a single pCPU. > > Jan What is the justification for removing it? c/s 18266:d31546a3883e has no explanation. This is now resulting in a command line parameter with "max" in its name acting unlike all other "max" parameters. There is certainly an argument for introducing a "dom0_cpus" parameter for setting an exact number, but I feel that this behavior is wrong for a parameter with "max" in its name. -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com