Hi Lidong, What do you mean by 'send the same traffic load between...' ? See if my understanding is correct: You have two identical physical machines (CPU/Memory/NIC...), one(A) runs RHEL6 Beta2(2.6.32-60) and the other one (B) runs RHEL6 (2.6.32-71). Each machine booted 5 identical VMs and then VMs on machine A (pool A) paired up with VMs on machine B (pool B). Sending packets between two VM pools yielded 20% utilization difference. Did you test bi-direction traffic, i.e. first pool A sends and pool B receives then vice versa? Regards, HUANG, Zhiteng -----Original Message----- From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On Behalf Of lidong chen Sent: Tuesday, November 23, 2010 10:14 AM To: tj@xxxxxxxxxx; sri@xxxxxxxxxx; mst@xxxxxxxxxx; Avi Kivity; kvm@xxxxxxxxxxxxxxx Subject: Performance test result between per-vhost kthread disable and enable I test the performance between per-vhost kthread disable and enable. Test method: Send the same traffic load between per-vhost kthread disable and enable, and compare the cpu rate of host os. I run five vm on kvm, each of them have five nic. the vhost version which per-vhost kthread disable we used is rhel6 beta 2(2.6.32.60). the vhost version which per-vhost kthread enable we used is rhel6 (2.6.32-71). Test result: with per-vhost kthread disable, the cpu rate of host os is 110%. with per-vhost kthread enable, the cpu rate of host os is 130%. In 2.6.32.60,the whole system only have a kthread. [root@rhel6-kvm1 ~]# ps -ef | grep vhost root 973 2 0 Nov22 ? 00:00:00 [vhost] In 2.6.32.71,the whole system have 25 kthread. [root@kvm-4slot ~]# ps -ef | grep vhost- root 12896 2 0 10:26 ? 00:00:00 [vhost-12842] root 12897 2 0 10:26 ? 00:00:00 [vhost-12842] root 12898 2 0 10:26 ? 00:00:00 [vhost-12842] root 12899 2 0 10:26 ? 00:00:00 [vhost-12842] root 12900 2 0 10:26 ? 00:00:00 [vhost-12842] root 13022 2 0 10:26 ? 00:00:00 [vhost-12981] root 13023 2 0 10:26 ? 00:00:00 [vhost-12981] root 13024 2 0 10:26 ? 00:00:00 [vhost-12981] root 13025 2 0 10:26 ? 00:00:00 [vhost-12981] root 13026 2 0 10:26 ? 00:00:00 [vhost-12981] root 13146 2 0 10:26 ? 00:00:00 [vhost-13088] root 13147 2 0 10:26 ? 00:00:00 [vhost-13088] root 13148 2 0 10:26 ? 00:00:00 [vhost-13088] root 13149 2 0 10:26 ? 00:00:00 [vhost-13088] root 13150 2 0 10:26 ? 00:00:00 [vhost-13088] ... Code difference: In 2.6.32.60,in function vhost_init, create the kthread for vhost. vhost_workqueue = create_singlethread_workqueue("vhost"); In 2.6.32.71,in function vhost_dev_set_owner, create the kthread for each nic interface. dev->wq = create_singlethread_workqueue(vhost_name); Conclusion: with per-vhost kthread enable, the system can more throughput. but deal the same traffic load with per-vhost kthread enable, it waste more cpu resource. In my application scene, the cpu resource is more important, and one kthread for deal with traffic load is enough. So i think we should add a param to control this. for the CPU-bound system, this param disable per-vhost kthread. for the I/O-bound system, this param enable per-vhost kthread. the default value of this param is enable. If my opinion is right, i will give a patch for this. -- 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 -- 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
