Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?

[Gleb Natapov <gleb@redhat.com>]

On Tue, Aug 03, 2010 at 12:13:06PM +0100, Richard W.M. Jones wrote:
> 
> qemu compiled from today's git.  Using the following command line:
> 
> $qemudir/x86_64-softmmu/qemu-system-x86_64 -L $qemudir/pc-bios \
>     -drive file=/dev/null,if=virtio \
>     -enable-kvm \
>     -nodefaults \
>     -nographic \
>     -serial stdio \
>     -m 500 \
>     -no-reboot \
>     -no-hpet \
>     -net user,vlan=0,net=169.254.0.0/16 \
>     -net nic,model=ne2k_pci,vlan=0 \
>     -kernel /tmp/libguestfsEyAMut/kernel \
>     -initrd /tmp/libguestfsEyAMut/initrd \
>     -append 'panic=1 console=ttyS0 udevtimeout=300 noapic acpi=off printk.time=1 cgroup_disable=memory selinux=0 guestfs_vmchannel=tcp:169.254.2.2:35007 guestfs_verbose=1 TERM=xterm-color '
> 
> With kernel 2.6.35 [*], this takes about 1 min 20 s before the guest
> starts.
> 
> If I revert back to kernel 2.6.34, it's pretty quick as usual.
> 
> strace is not very informative.  It's in a loop doing select and
> reading/writing from some file descriptors, including the signalfd and
> two pipe fds.
> 
> Anyone seen anything like this?
> 
I assume your initrd is huge. In newer kernels ins/outs are much slower that
they were. They are much more correct too. It shouldn't be 1 min 20 sec for
100M initrd though, but it can take 20-30 sec. This belongs to kvm list BTW.

--
			Gleb.