Michael Tokarev wrote: > René Pfeiffer wrote: >> Hello! >> >> I just tested qemu-kvm-0.11.0 with the KVM module of kernel 2.6.31.1. I >> noticed that the I/O performance of an unattended stock Debian Lenny >> install dropped somehow. The test machines ran with kvm-88 and 2.6.30.x >> before. The difference is very noticeable (went from about 5 minutes up >> to 15-25 minutes). The two test machines have different CPUs (one is an >> Intel Core2 CPU, the other runs with an AMD Athlon 64 X2 Dual). >> >> Is this the effect of added code regarding caching/data integrity to the >> VirtIO block layer or somewhere else? The qemu-system-x86_64 seems to >> hang a lot more in heavy I/O (showing 'D' in top/htop). >> >> The command line is quite straight-forward: >> qemu-system-x86_64 -drive file=debian.qcow2,if=virtio,boot=on -cdrom \ >> /srv/isos/debian-502-i386-netinst.iso -smp 2 -boot d -m 512 -net nic \ >> -net user -usb > ^^^^^^^^^ > > Care to try with something more real than user-level networking? > You're using netinstall which - apparently - tries to use some > networking d/loading components etc, and userlevel networking is > known to be very very slow.... It can be particularly slow if you use in-kernel irqchips and the default NIC emulation (up to 10 times slower), some effect I always wanted to understand on a rainy day. So, when you actually want -net user, try -no-kvm-irqchip. Jan
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