At this point, I'd suggest testing vhost-net on the upstream kernel,
not on rhel kernels. The change that introduced per-device threads is:
c23f3445e68e1db0e74099f264bc5ff5d55ebdeb
i will try this tomorrow.
Is CONFIG_SCHED_DEBUG set?
yes. CONFIG_SCHED_DEBUG=y.
2010/11/23 Michael S. Tsirkin <mst@xxxxxxxxxx>:
> On Tue, Nov 23, 2010 at 10:13:43AM +0800, lidong chen wrote:
>> 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).
>
> At this point, I'd suggest testing vhost-net on the upstream kernel,
> not on rhel kernels. The change that introduced per-device threads is:
> c23f3445e68e1db0e74099f264bc5ff5d55ebdeb
>
>> 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%.
>
> Is CONFIG_SCHED_DEBUG set? We are stressing the scheduler a lot with
> vhost-net.
>
>> 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.
>
> Let's try to figure out what the issue is, first.
>
> --
> MST
>
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