[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] KVM VM(rhel-5.5) %si is too high when TX/RX packets
From: |
Zhanghaoyu (A) |
Subject: |
[Qemu-devel] KVM VM(rhel-5.5) %si is too high when TX/RX packets |
Date: |
Fri, 3 May 2013 04:05:01 +0000 |
I running a VM(RHEL-5.5) on KVM hypervisor(linux-3.8 + QEMU-1.4.1), and
direct-assign intel 82576 VF to the VM. When TX/RX packets on VM to the other
host via iperf tool, top tool result on VM shown that the %si is too high,
approximately 95% ~ 100%, but from the view of host, the VM's total CPU usage
is about 20% - 30%. And the throughput rate is approximately 200Mb/s, far from
the line rate 1Gb/s,
And, I found the hardirq rate is lower than normal by running "watch -d -n 1
cat /proc/interrupts", I think it's caused by the too high %si, because the
NIC's hardirq was disabled during the softirq process.
Then, I direct-assign the intel 82576 to the VM, the same case happened too.
I found the intel 82576 and intel 82576 VF's interrupt mode are both PCI-MSI-X.
And,
I rmmod the igb driver, and, re-insmod the igb driver(igb-4.1.2) with the
parameter IntMode=0/1(0:legacy, 1:MSI, 2:MSI-x), the problem then gone, the %si
is approximately 20% -30%, and the throughput rate came to the line rate, about
940Mb/s.
I update the VM to RHEL-6.1, the problem disappeared too.
And, I found a very strange thing, the VM's 82576VF's irq routing is set one
time on Vf's one interrupt received, so frequently.
Thanks,
Zhang Haoyu
- [Qemu-devel] KVM VM(rhel-5.5) %si is too high when TX/RX packets,
Zhanghaoyu (A) <=