From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuehai Xu Subject: Re: Question about the ability of credit scheduler to handle I/O and CPU intensive VMs Date: Thu, 30 Sep 2010 08:28:47 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: George Dunlap Cc: xen-devel@lists.xensource.com, yhxu@wayne.edu List-Id: xen-devel@lists.xenproject.org On Tue, Sep 14, 2010 at 5:22 AM, George Dunlap wrote: > Credit2 development is mostly stalled; I've just got too many other > things to do at the moment. =A0If you know someone good at hypervisor > development that wants to move to Cambridge to help me out, I think we > have some open positions... :-) > > The problem you describe, which I call the "mixed workload" problem, > is something that I'd like to try to solve with credit2. =A0The actual > problem with credit1, at the moment, is that when a vcpu is scheduled > to run, it can always run for 30ms if it wants to. =A0So if it's a CPU > burner, in order to give it 50%, you have to keep it from running for > 30ms before letting it run for 30ms again. > > I agree, letting a VM with an interrupt run for a short period of time > makes sense. =A0The challenge is to make sure that it can't simply send > itself interrupts every 50us and get to run 100% of the time. :-) I am afraid I don't really understand the challenge is, or, in another word, this method is good principally, but in practice, it is hard to implement? As I know, the OS should always schedules I/O related processes once they are in runnable queue, so, as long as we give even a very short period of time to the waken up guest VM, the I/O process in it should be scheduled at once. In that case, this problem should be solved. Of course, I don't do experiments, saying is always much easier than doing. Thanks, Yuehai > > I don't have time to work on this right now, but if you work up some > patches, I can give you feedback. =A0Be advised, that getting this stuff > to work right is not easy. > > =A0-George