From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: Offline state in scheduling Date: Tue, 29 Jun 2010 13:50:12 +0100 Message-ID: <4C29EC04.9000403@eu.citrix.com> References: <201006281159133905493@gmail.com> <201006291942243126656@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201006291942243126656@gmail.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "duyuyang@gmail.com" Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On 29/06/10 12:42, Yuyang Du wrote: > Is it right to say the time HVM waits for I/O equals the offline time (given no administrator pauses)? There are some I/O events that are handled inside of Xen (such as APIC accesses); these don't cause a vcpu to be paused. I think in the normal course of operation, an HVM vcpu is only paused when doing I/O. Other reasons might be administrator pause, migration, save/restore, domain creation, memory sharing / page swapping, and so on. But if you aren't doing any of those, I think I/O done in QEMU would be the only reason. > I am testing apache web server in a HVM, and I find that vcpu blocking state makes up a large portion. Since the HVM can not issue SCHED_block hypercalls, so the blocking state means the VM is not cpu intensive and often executes HLT to halt itself? Yes. If you take a trace to include VMX / SVM events, and use xenalyze, you should be able to see the HLT vmexit before blocking. -George