From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Catterall Subject: Re: [PATCH RFC v2 0/4] HVM x86 deprivileged mode operations Date: Mon, 7 Sep 2015 11:50:55 +0100 Message-ID: <55ED6C0F.90100@citrix.com> References: <1441296086-18209-1-git-send-email-Ben.Catterall@citrix.com> <55E87236.4020705@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZYu0r-0003zb-NQ for xen-devel@lists.xenproject.org; Mon, 07 Sep 2015 10:51:01 +0000 In-Reply-To: <55E87236.4020705@citrix.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: David Vrabel , xen-devel@lists.xenproject.org Cc: keir@xen.org, jbeulich@suse.com, george.dunlap@eu.citrix.com, andrew.cooper3@citrix.com, tim@xen.org, Aravind.Gopalakrishnan@amd.com, suravee.suthikulpanit@amd.com, boris.ostrovsky@oracle.com, ian.campbell@citrix.com List-Id: xen-devel@lists.xenproject.org On 03/09/15 17:15, David Vrabel wrote: > On 03/09/15 17:01, Ben Catterall wrote: >> >> Intel Intel 2.2GHz Xeon E5-2407 0 processor: >> -------------------------------------------- >> 1.55e-06 seconds was the average time for performing the write without the >> deprivileged code running. >> >> 5.75e-06 seconds was the average time for performing the write with the >> deprivileged code running. >> >> So approximately 351% overhead >> >> AMD Opteron 2376: >> ----------------- >> 1.74e-06 seconds was the average time for performing the write without the >> deprivileged code running. >> 3.10e-06 seconds was the average time for performing the write with an entry and >> exit from deprvileged mode. >> >> So approximately 178% overhead. > > How does this compare to the overhead of passing the I/O through to qemu? > So, passing this portio op through to QEMU takes roughly 20e-6 seconds. However, I don't know if the emulator would have gone and prodded a physical port as port of that which could skew the result. I'll look into this and get back if I find anything to clarify this. Ben > David >