From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Poor HVM performance with 8 vcpus Date: Wed, 07 Oct 2009 08:55:05 +0200 Message-ID: <4ACC3B49.4060500@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: 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, we've got massive performance problems running a 8 vcpu HVM-guest (BS2000) under XEN (xen 3.3.1). With a specific benchmark producing a rather high load on memory management operations (lots of process creation/deletion and memory allocation) the 8 vcpu performance was worse than the 4 vcpu performance. On other platforms (/390, MIPS, SPARC) this benchmark scaled rather well with the number of cpus. The result of the usage of the software performance counters of XEN seemed to point to the shadow lock being the reason. I modified the Hypervisor to gather some lock statistics (patch will be sent soon) and found that the shadow lock is really the bottleneck. On average 4 vcpus are waiting to get the lock! Is this a known issue? Is there a chance to split the shadow lock into sub-locks or to use a reader/writer lock instead? I just wanted to ask before trying to understand all of the shadow code :-) Juergen -- Juergen Gross Principal Developer Operating Systems TSP ES&S SWE OS6 Telephone: +49 (0) 89 636 47950 Fujitsu Technolgy Solutions e-mail: juergen.gross@ts.fujitsu.com Otto-Hahn-Ring 6 Internet: ts.fujitsu.com D-81739 Muenchen Company details: ts.fujitsu.com/imprint.html