[libvirt] TSO of VM packets degardes significantly on increasing VM's on a Host

Hi, Problem- Offloading for VM packets (TSO enabled in VM's ) degrades severely with increase in VM's on a host What is controlling the offloading of VM packets and how can we improve it ? ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Description- We have a testbed OpenStack deployment. We boot 1, 10 and 25 VM's on a single compute node and start iperf traffic. ( VM's are iperf client ). We then simultaneously do tcpdump at the veth-pair connecting the VM to the OVS Bridges. Tcpdump data shows that on increasing the VM's on a host, the % of offloaded packets degrades severely ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Host configuration- 12 cores ( 24 vCPU ), 40 GB RAM [root@rhel7-25 ~]# uname -a Linux rhel7-25.in.ibm.com 3.10.0-229.el7.x86_64 #1 SMP Thu Jan 29 18:37:38 EST 2015 x86_64 x86_64 x86_64 GNU/Linux VM MTU is set to 1450 ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Analysis- ------------------------------------------------------------------------------------ | VMs | % Non-Offloaded packets | |-----------------------------------------------------------------------------------| | 1 | 11.11% | | 10 | 71.78% | | 25 | 80.44% | |-----------------------|-----------------------------------------------------------| Thus we see significant degradation in offloaded packets when 10 and 25 VM's are sending iperf data simultaneously. ( TSO enabled VM's ) Non-Offloaded packets means Ethernet Frame of size 1464 ( VM MTU is 1450 ) ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Tcpdump details- Iperf Server IP- 1.1.1.34 For 1 VM, we see majority offloaded packets- [piyush@rhel7-34 25]$ cat qvoed7aa38d-22.log | grep "> 1.1.1.34.5001" | head -n 30 14:36:26.331073 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 74: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 0 14:36:26.331917 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 66: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 0 14:36:26.331946 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 90: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 24 14:36:26.331977 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 7056: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 6990 14:36:26.332018 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 5658: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 5592 14:36:26.332527 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 7056: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 6990 14:36:26.332560 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 9852: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 9786 14:36:26.333024 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 8454: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 8388 14:36:26.333054 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 7056: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 6990 14:36:26.333076 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 4260: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 4194 14:36:26.333530 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 16842: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 16776 14:36:26.333568 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 4260: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 4194 14:36:26.333886 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 21036: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 20970 14:36:26.333925 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 2862: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 2796 14:36:26.334303 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 21036: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 20970 14:36:26.334349 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 2862: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 2796 14:36:26.334741 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 22434: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 22368 14:36:26.335118 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 25230: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 25164 14:36:26.335566 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 25230: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 25164 14:36:26.336007 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 23832: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 23766 14:36:26.336050 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 2862: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 2796 14:36:26.336453 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 26628: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 26562 14:36:26.336898 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 22434: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 22368 14:36:26.336941 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 5658: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 5592 14:36:26.337235 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 23832: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 23766 14:36:26.337603 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 21036: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 20970 14:36:26.337644 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 8454: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 8388 14:36:26.337987 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 18240: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 18174 14:36:26.338040 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 12648: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 12582 14:36:26.338356 fa:16:3e:98:41:8b > fa:16:3e:ef:5f:16, IPv4, length 14046: 10.20.7.3.50395 > 1.1.1.34.5001: tcp 13980 For 20 VM's, we see reduction is size of offloaded packets. Tcpdump for one of the 10 VM's- [piyush@rhel7-34 25]$ cat qvo255d8cdd-90.log | grep "> 1.1.1.34.5001" | head -n 30 15:09:25.024790 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 74: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 0 15:09:25.026834 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 66: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 0 15:09:25.026870 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 90: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 24 15:09:25.027186 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.027213 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 5658: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 5592 15:09:25.032500 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 5658: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 5592 15:09:25.032539 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 1464: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 1398 15:09:25.032567 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.035122 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.035631 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.035661 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.038508 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.038904 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.039300 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.040740 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 4260: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 4194 15:09:25.040774 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 2862: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 2796 15:09:25.040995 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.041235 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.042599 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.043209 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.043592 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.044312 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.044551 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.045232 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.045251 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.049951 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 5658: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 5592 15:09:25.049977 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 1464: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 1398 15:09:25.049996 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 7056: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 6990 15:09:25.050020 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 2862: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 2796 15:09:25.050039 fa:16:3e:b9:f8:ec > fa:16:3e:c1:de:cc, IPv4, length 4260: 10.20.18.3.36798 > 1.1.1.34.5001: tcp 4194 For 25 VM's, we hardly see very less offloaded packets. Tcpdump for one of the 25 VM's- 15:52:31.543613 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.543637 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 2862: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 2796 15:52:31.543957 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 2862: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 2796 15:52:31.544090 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 4260: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 4194 15:52:31.544272 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.544296 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.544316 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.544340 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545034 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545066 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 5658: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 5592 15:52:31.545474 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545501 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 2862: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 2796 15:52:31.545539 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 2862: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 2796 15:52:31.545572 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 7056: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 6990 15:52:31.545736 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545807 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545813 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545934 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545956 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.545974 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 15:52:31.546012 fa:16:3e:3c:7d:78 > fa:16:3e:aa:af:d5, IPv4, length 1464: 10.20.10.3.45892 > 1.1.1.34.5001: tcp 1398 Thanks and regards, Piyush Raman Mail: pirsriva(a)in.ibm.com