netdev - Re: [PATCH net-next v3] net: dqs: introduce IFF_NO

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Date: Thu, 13 Jun 2024 17:48:50 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Jakub Kicinski <kuba@...nel.org>, pabeni@...hat.com, davem@...emloft.net, 
	dsahern@...nel.org, mst@...hat.com, jasowang@...hat.com, 
	xuanzhuo@...ux.alibaba.com, eperezma@...hat.com, leitao@...ian.org, 
	netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v3] net: dqs: introduce IFF_NO_BQL private flag
 for non-BQL drivers

On Thu, Jun 13, 2024 at 5:37 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> On Thu, Jun 13, 2024 at 11:26 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > On Thu, Jun 13, 2024 at 5:02 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > >
> > > On Thu, 13 Jun 2024 22:55:16 +0800 Jason Xing wrote:
> > > > I wonder why the status of this patch was changed to 'Changes
> > > > Requested'? Is there anything else I should adjust?
> > >
> > > Sorry to flip the question on you, but do you think the patch should
> > > be merged as is? Given Jiri is adding BQL support to virtio?
> >
> > Also what is the rationale for all this discussion ?
> >
> > Don't we have many sys files that are never used anyway ?
>
> At the very beginning, I thought the current patch is very simple and
> easy to get merged because I just found other non-BQL drivers passing
> the checks in netdev_uses_bql(). Also see the commit:

>     Suggested-by: Eric Dumazet <edumazet@...gle.com>
>     Signed-off-by: Breno Leitao <leitao@...ian.org>
>     Link: https://lore.kernel.org/r/20240216094154.3263843-1-leitao@debian.org
>     Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>
> I followed this patch and introduced a flag only.
>
> Actually, it's against my expectations. It involved too many
> discussions. As I said again: at the very beginning, I thought it's
> very easy to get merged... :(

I think you missed the point of the original suggestion leading to Breno patch.

At Google, we create gazillion of netns per minute, with few virtual
drivers in them (like loopback, ipvlan)

This was pretty easy to avoid /sys/class/net/lo/queues/tx-0/byte_queue_limits/*
creation. cpu savings for little investment.

But when it comes to physical devices, I really do not see the benefit
of being picky about some sysfs files.

So let me repeat my question : Why do you need this ?