Messages in this thread | | | From | "Li, Liang Z" <> | Subject | RE: about the time consuming kvm_vcpu_ioctl issue in rhel kernel | Date | Thu, 6 Aug 2015 05:38:23 +0000 |
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The synchronize_rcu() is a time consuming operation, the unpstream kernel still have some issue, the KVM_RUN ioctl will take more then 10ms when resume the VM after migration.
Liang
> -----Original Message----- > From: Li, Liang Z > Sent: Thursday, August 06, 2015 11:47 AM > To: 'Paolo Bonzini'; 'Juan Quintela'; linux-kernel@vger.kernel.org > Cc: Zhang, Yang Z; kvm@vger.kernel.org > Subject: about the time consuming kvm_vcpu_ioctl issue in rhel kernel > > Hi Paolo & Juan, > > I found some of the kvm_vcpu_ioctl operation takes about more than 10ms > with the 3.10.0-229.el7.x86_64 kernel, which prolong the VM service > downtime when doing live migration about 20~30ms. > This happened when doing the KVM_KVMCLOCK_CTRL ioctl. It's worse if > more VCPUs used by guest(4VPUs in my test). The upstream kernel does not > have this issue because of the patch 7a72f7a140bfd3, maybe this patch > should be backported to the el7 kernel. > > Liang
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