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

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Message-ID: <CACGkMEv88U1_2K2b0KdmH97gfrdOvK_1ajqh=UTK6=KgZ4OYvQ@mail.gmail.com>
Date: Mon, 25 Mar 2024 15:56:26 +0800
From: Jason Wang <jasowang@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.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

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.

Thanks

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