On 08/25/2010 06:09 PM, walt wrote:
On 08/25/2010 12:48 PM, Anthony Liguori wrote:
On 08/25/2010 02:37 PM, walt wrote:
Hi qemu team,
I just discovered that qemu now offers kvm support, so I decided to
compare it to qemu-kvm.
I'm running the latest git versions of both programs on an AMD64
host running the latest kernel from Linus.git.
The guest is Windows 7 on a qcow2 disk image and one kvm64 cpu.
I find that qemu-kvm boots to the Win7 login prompt in 25 seconds,
>> while qemu with kvm enabled takes about 45 seconds.
make sure you build qemu with --enable-io-thread.
I built qemu both with and without io-thread, and it makes no difference
at least in this particular experiment.
(BTW, I found that qemu-kvm will not even compile with --enable-io-thread
because qemu_mutex_lock_iothread becomes defined in two places.)
Also, what's your full command line?
For qemu:
/usr/local/bin/qemu-system-x86_64 -m 1024 -enable-kvm -cpu kvm64 w7.diff
For qemu-kvm:
/home/wa1ter/bin/qemu-system-x86_64 -m 1024 -enable-kvm -cpu kvm64
w7.diff
You'll get more accurate and repeatable results by using:
qemu-system-x86_64 -m 1024 -enable-kvm -cpu kvm64 -drive
file=w7.diff,cache=none
Also try qemu-kvm with -no-kvm-irqchip. I can't believe an in-kernel
lapic would make this much of a difference with windows 7 but it's worth
trying.
Regards,
Anthony Liguori
Note that w7.diff is the same file in both cases: a qcow2 differencing
disk
made from the original qcow2 backing file w7.img.
Thanks for your reply. I'm curious if anyone can reproduce this
difference
in speed.
