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

[Richard W.M. Jones]

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?

Rich.

[*] This Fedora kernel:
http://koji.fedoraproject.org/koji/buildinfo?buildID=187085

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://et.redhat.com/~rjones/libguestfs/
See what it can do: http://et.redhat.com/~rjones/libguestfs/recipes.html