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@xxxxxxxxxxxxxxx > Cc: Zhang, Yang Z; kvm@xxxxxxxxxxxxxxx > 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 -- 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
