Hello, jenkins.debian.net is running inside a KVM VM, and it runs nested KVM guests for its installation attempts. This goes fine with Linux kernels, but it is extremely slow with gnumach kernels. I have reproduced the issue with my laptop with a linux 3.17 host kernel, a 3.16 L1-guest kernel, and an i7-2720QM CPU, with similar results; it's actually even slower than letting qemu emulate the CPU... For these tests I'm using the following image: http://people.debian.org/~sthibault/tmp/netinst.iso The reference test here boils down to running qemu -cdrom netinst.iso -m 512, choosing the "Automated install" choice, and waiting for "Loading additional components" step to complete. (yes, the boot menu gets mangled ATM, there's apparently currently a bug between qemu and grub) My host is A, my level1-KVM-guest is B. KVM: A$ qemu -enable-kvm -cdrom netinst.iso -m 512M takes ~1 minute. QEMU: A$ qemu -cdrom netinst.iso -m 512M takes ~7 minutes. KVM-in-KVM: B$ qemu -enable-kvm -cdrom netinst.iso -m 512M takes ~10 minutes, when it doesn't gets completely stuck, which is quite often, actually... QEMU-in-KVM: B$ qemu -cdrom netinst.iso -m 512M takes ~7 minutes. I don't see such horrible slowdown with a linux image. Is there something particular that could explain such a difference? What tools or counters could I use to investigate which area of KVM is getting slow? Samuel -- 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
