netdev - Re: [PATCH 2/2] virtio-net: reduce the CPU consumption of dim worker

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Date: Mon, 25 Mar 2024 16:22:17 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux.dev,
 "Michael S. Tsirkin" <mst@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
 "David S. Miller" <davem@...emloft.net>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH 2/2] virtio-net: reduce the CPU consumption of dim worker



在 2024/3/25 下午3:56, Jason Wang 写道:
> On Mon, Mar 25, 2024 at 3:18 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>>
>>
>> 在 2024/3/25 下午1:57, Jason Wang 写道:
>>> On Mon, Mar 25, 2024 at 10:21 AM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>>>>
>>>> 在 2024/3/22 下午1:19, Jason Wang 写道:
>>>>> On Thu, Mar 21, 2024 at 7:46 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
>>>>>> Currently, ctrlq processes commands in a synchronous manner,
>>>>>> which increases the delay of dim commands when configuring
>>>>>> multi-queue VMs, which in turn causes the CPU utilization to
>>>>>> increase and interferes with the performance of dim.
>>>>>>
>>>>>> Therefore we asynchronously process ctlq's dim commands.
>>>>>>
>>>>>> Signed-off-by: Heng Qi <hengqi@...ux.alibaba.com>
>>>>> I may miss some previous discussions.
>>>>>
>>>>> But at least the changelog needs to explain why you don't use interrupt.
>>>> Will add, but reply here first.
>>>>
>>>> When upgrading the driver's ctrlq to use interrupt, problems may occur
>>>> with some existing devices.
>>>> For example, when existing devices are replaced with new drivers, they
>>>> may not work.
>>>> Or, if the guest OS supported by the new device is replaced by an old
>>>> downstream OS product, it will not be usable.
>>>>
>>>> Although, ctrlq has the same capabilities as IOq in the virtio spec,
>>>> this does have historical baggage.
>>> I don't think the upstream Linux drivers need to workaround buggy
>>> devices. Or it is a good excuse to block configure interrupts.
>> Of course I agree. Our DPU devices support ctrlq irq natively, as long
>> as the guest os opens irq to ctrlq.
>>
>> If other products have no problem with this, I would prefer to use irq
>> to solve this problem, which is the most essential solution.
> Let's do that.

Ok, will do.

Do you have the link to the patch where you previously modified the 
control queue for interrupt notifications.
I think a new patch could be made on top of it, but I can't seem to find it.

Thanks,
Heng

>
> Thanks
>
>>> And I remember you told us your device doesn't have such an issue.
>> YES.
>>
>> Thanks,
>> Heng
>>
>>> Thanks
>>>
>>>> Thanks,
>>>> Heng
>>>>
>>>>> Thanks