netdev - Re: [PATCH net-next v2] drivers, ixgbe: show VF statistics

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Message-ID: <20220509073915.28476-1-mheyne@amazon.de>
Date:   Mon, 9 May 2022 07:39:15 +0000
From:   Maximilian Heyne <mheyne@...zon.de>
To:     Tony Nguyen <anthony.l.nguyen@...el.com>
CC:     Jakub Kicinski <kuba@...nel.org>,
        Maximilian Heyne <mheyne@...zon.de>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2] drivers, ixgbe: show VF statistics

On 2022-05-06T09:20:14-07:00   Tony Nguyen <anthony.l.nguyen@...el.com> wrote:
> On 5/6/2022 9:13 AM, Jakub Kicinski wrote:
> > On Fri, 6 May 2022 06:44:40 +0000 Maximilian Heyne wrote:
> >> On 2022-05-04T20:16:32-07:00   Jakub Kicinski <kuba@...nel.org> wrote:
> >>
> >>> On Tue, 3 May 2022 15:00:17 +0000 Maximilian Heyne wrote:
> >>>> +		for (i = 0; i < adapter->num_vfs; i++) {
> >>>> +			ethtool_sprintf(&p, "VF %u Rx Packets", i);
> >>>> +			ethtool_sprintf(&p, "VF %u Rx Bytes", i);
> >>>> +			ethtool_sprintf(&p, "VF %u Tx Packets", i);
> >>>> +			ethtool_sprintf(&p, "VF %u Tx Bytes", i);
> >>>> +			ethtool_sprintf(&p, "VF %u MC Packets", i);
> >>>> +		}
> >>>
> >>> Please drop the ethtool stats. We've been trying to avoid duplicating
> >>> the same stats in ethtool and iproute2 for a while now.
> >>
> >> I can see the point that standard metrics should only be reported via the
> >> iproute2 interface. However, in this special case this patch was
> >> intended to converge the out-of-tree driver with the in-tree version.
> >> These missing stats were breaking our userspace. If we now switch
> >> solely to iproute2 based statistics both driver versions would
> >> diverge even more. So depending on where a user gets the ixgbe driver
> >> from, they have to work-around.
> >>
> >> I can change the patch as requested, but it will contradict the inital
> >> intention. At least Intel should then port this change to the
> >> external driver as well. Let's get a statement from them.
> 
> We discussed this patch internally and concluded the correct approach 
> would be to not have the ethtool stats and use the VF info. Jakub beat 
> us to the comment. We would plan to port the iproute implementation to 
> OOT as well.

Ok, then I'll send a follow-up patch without the ethtool changes. I'm happy to
get some kind of convergence between the out-of-tree driver and upstream. 

While at it, I wonder whether other drivers need similar changes as well and
what other features are missing in the upstream driver. There should be no
surprises when switching between these drivers.

> 
> > Ack, but we really want people to move towards using standard stats.
> > 
> > Can you change the user space to first try reading the stats via
> > iproute2/rtnetlink? And fallback to random ethtool strings if not
> > available? That way it will work with any driver implementing the
> > standard API. Long term that'll make everyone's life easier.

Yes, in this case we are in control of user space and can work around.

> > 
> > Out-of-tree code cannot be an argument upstream, otherwise we'd
> > completely lose control over our APIs. Vendors could ship whatever
> > in their out of tree repo and then force us to accept it upstream.
> > 
> > It's disappointing to see the vendor letting the uAPI of the out of
> > tree driver diverge from upstream, especially a driver this mature.
> 



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