Hi Dor, Thank you very much for your reply! Our kernel of host os was based on 2.6.18, so cgroup is not avaialbe for us. And our Intel chip supports constant_tsc. We will run RHEL 5.4 as guest os. Will the clock of guest os still be a issue if we use kvm-clock in guest os? And does it mean guest os will always has clock issue, if vcpu thread was not scheduled on time? Thanks, Yu On 08/17/2009 08:09 AM, Yu Jiang (yujia) wrote: > Hi KVM experts, > > Our user case needs to run KVM and application on host together. To > reserve some CPU resource for application, we want to limit the CPU > usage of KVM. Without KVM CPU usage limitation, the idle CPU of host > OS becomes 0% in peak time. > > I have searched this topic on internet, but didn't find much comments. > > One possible solution could be managing KVM process as regular process > on host OS, and use tool like http://cpulimit.sourceforge.net/ to > limit maximum CPU usage of VM. Basically, the cpulimit tool use SIGSTP > and SIGCONT signals to stop and resume the execution of KVM process. > It works fine for us at moment. But, I feel there may be some risk to > do this, because the signal will cause whole process of KVM paused(not > only vcpu thread). Do you think it's safe to use cpulimit kinds of > tool to SIGSTP/SIGCONT kvm? > > Another possible solution was: > Enhance QEMU user space to monitor the CPU usage of itself, and use > existing way(pause_all_vcpus?) to pause vcpu thread of KVM in case KVM > reaches CPU usage limitation. Is this solution possible? A mgmt daemon can control qemu using the monitor and stop/cont it on these cases. The main problem with the two solutions above is that the guest clock might drift. Moreover, you increase the latency for the guest OS/applications. You can use the 'nice' command to priorities the host applications. For newer kernels you should use cgroups that solves this specific issue exactly. > > Any idea? > > > Thanks, > Yu > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in the > body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
