On Tue, 2008-09-16 at 09:16 -0500, Anthony Liguori wrote:
> Ben-Ami Yassour wrote:
> > I am running virtio with the latest KVM code, and see a significant
> > performance issue.
> >
> > Ping to the host (or any other close machine) reports a 4ms delay.
> >
>
> What kvm version and what host kernel version?
>
> It's very easy to mistakenly compile qemu without GSO support too. You
> have to make sure that the 2.6.27 if_tun.h is being included by QEMU.
Is there an option to control GSO support? How?
I am using the kernel and userspace that I pulled from the kvm tree
today.
Based on your comment, we checked and the build of the userspace does
not take if_tun.h from the kernel tree, it takes it from the system
include files.
The reason was that the file was not copied as part of the userspace
build.
To fix this we made the following change:
diff --git a/kernel/Makefile b/kernel/Makefile
index 3f5f6da..b81b098 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -53,7 +53,7 @@ T = $(subst -sync,,$@)-tmp
header-sync:
rm -rf $T
rsync -R \
- "$(LINUX)"/./include/linux/kvm*.h \
+ "$(LINUX)"/./include/linux/*.h \
"$(LINUX)"/./include/asm-*/kvm*.h \
Even with this change and compiling the userspace with the correct
if_tun.h the results are the same, ping takes 4ms.
What could be the reason?
Thanks,
Ben
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