Hi, I deployed KVM on my Gentoo servers for performance testing, but I am now having high latency problems with the VirtIO NIC: diggle7 is the KVM host, diggle6 is another physical host in the same physical network, and app211 is a KVM guest running on diggle7. ------------------------------- ping statistics ------------------------------- diggle7 ~ # ping -c 5 app211 PING app211 (192.168.1.211) 56(84) bytes of data. 64 bytes from app211 (192.168.1.211): icmp_seq=1 ttl=64 time=0.454 ms 64 bytes from app211 (192.168.1.211): icmp_seq=2 ttl=64 time=0.097 ms 64 bytes from app211 (192.168.1.211): icmp_seq=3 ttl=64 time=0.248 ms 64 bytes from app211 (192.168.1.211): icmp_seq=4 ttl=64 time=0.355 ms 64 bytes from app211 (192.168.1.211): icmp_seq=5 ttl=64 time=0.494 ms --- app211 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 3998ms rtt min/avg/max/mdev = 0.097/0.329/0.494/0.145 ms diggle7 ~ # ping -c 5 diggle6 PING diggle6 (192.168.1.44) 56(84) bytes of data. 64 bytes from diggle6 (192.168.1.44): icmp_seq=1 ttl=64 time=0.101 ms 64 bytes from diggle6 (192.168.1.44): icmp_seq=2 ttl=64 time=0.076 ms 64 bytes from diggle6 (192.168.1.44): icmp_seq=3 ttl=64 time=0.085 ms 64 bytes from diggle6 (192.168.1.44): icmp_seq=4 ttl=64 time=0.130 ms 64 bytes from diggle6 (192.168.1.44): icmp_seq=5 ttl=64 time=0.083 ms --- diggle6 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 3998ms rtt min/avg/max/mdev = 0.076/0.095/0.130/0.019 ms ------------------------------- ping statistics ------------------------------- as above, the latency between Host and KVM guest(0.3+ms on average) is much higher than the latency between the two physical hosts(~0.1ms on average), this might not be acceptable for latency sensitive applications, for example memcached. is the latency normal? or is there something wrong with my configuration? here is detailed information about my hardware and software environment: Host hardware: DELL R710 + Intel Xeon E5620 @2.40GHz + 96GB memory + BCM5709 GB Ethernet Host software: Gentoo amd64 + 2.6.36-gentoo-r5 + qemu-kvm-0.13.0 KVM related kernel configs for the host (diggle7): diggle7 ~ # zgrep -E "(VIRTIO|KVM)" /proc/config.gz CONFIG_VIRTIO_BLK=m CONFIG_VIRTIO_NET=m # CONFIG_VIRTIO_CONSOLE is not set CONFIG_HW_RANDOM_VIRTIO=m CONFIG_HAVE_KVM=y CONFIG_HAVE_KVM_IRQCHIP=y CONFIG_HAVE_KVM_EVENTFD=y CONFIG_KVM_APIC_ARCHITECTURE=y CONFIG_KVM_MMIO=y CONFIG_KVM=m CONFIG_KVM_INTEL=m # CONFIG_KVM_AMD is not set CONFIG_VIRTIO=m CONFIG_VIRTIO_RING=m CONFIG_VIRTIO_PCI=m CONFIG_VIRTIO_BALLOON=m Kernel modules loaded on the host: diggle7 ~ # lsmod Module Size Used by virtio_balloon 4098 0 tun 12809 2 bridge 63340 0 stp 1871 1 bridge llc 4595 2 bridge,stp drbd 181114 7 lru_cache 6273 1 drbd virtio_net 10812 0 virtio 3978 2 virtio_balloon,virtio_net virtio_ring 4692 2 virtio_balloon,virtio_net xt_state 1218 1 iptable_filter 1626 1 iptable_nat 3806 0 nf_nat 15835 1 iptable_nat nf_conntrack_ipv4 11106 4 iptable_nat,nf_nat nf_defrag_ipv4 1361 1 nf_conntrack_ipv4 iptable_mangle 1591 0 ipmi_devintf 7380 0 ipmi_si 37990 0 ipmi_msghandler 31256 2 ipmi_devintf,ipmi_si kvm_intel 42059 18 kvm 248729 1 kvm_intel fuse 58921 2 KVM related kernel configs for the guest (app211): app211 ~ # zgrep -E "(VIRTIO|KVM)" /proc/config.gz CONFIG_KVM_CLOCK=y CONFIG_KVM_GUEST=y CONFIG_VIRTIO_BLK=y CONFIG_VIRTIO_NET=y CONFIG_VIRTIO_CONSOLE=y CONFIG_HW_RANDOM_VIRTIO=y CONFIG_HAVE_KVM=y # CONFIG_KVM is not set CONFIG_VIRTIO=y CONFIG_VIRTIO_RING=y CONFIG_VIRTIO_PCI=y CONFIG_VIRTIO_BALLOON=y Command line for starting the KVM guest: diggle7 ~ # pgrep -fl qemu 18154 /usr/bin/qemu-system-x86_64 --enable-kvm -drive file=/vm/app211/app211.qcow2,if=virtio,boot=on,cache=writeback -cdrom /mfs/sysadmin/finnix.iso -boot c -vnc diggle7:211 -net nic,model=virtio,macaddr=52:54:C0:A8:01:D3 -net tap,ifname=app211,script=no -m 30720 -cpu host -smp 16 -daemonize any help will be appreciated. Thanks, Xupeng -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
