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From:   Long Li <longli@microsoft.com>
To:     Jakub Kicinski <kuba@kernel.org>
CC:     Greg KH <gregkh@linuxfoundation.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Leon Romanovsky <leon@kernel.org>,
        Ajay Sharma <sharmaajay@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>,
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        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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Subject: RE: [Patch v3] net: mana: Batch ringing RX queue doorbell on
 receiving packets
Thread-Topic: [Patch v3] net: mana: Batch ringing RX queue doorbell on
 receiving packets
Thread-Index: AQHZqInuIa+OQxGM80ioo4gKQGwCLa+hejgAgACaBvCAARhFAIAAZi9AgAAzZwCAAA42kIAAMnKAgALheSA=
Date:   Sun, 2 Jul 2023 20:18:25 +0000
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> Subject: Re: [Patch v3] net: mana: Batch ringing RX queue doorbell on rec=
eiving
> packets
>=20
> On Fri, 30 Jun 2023 20:42:28 +0000 Long Li wrote:
> > > > 5.15 and kernel 6.1. (those kernels are longterm) They need this
> > > > fix to achieve the performance target.
> > >
> > > Why can't they be upgraded to get that performance target, and all
> > > the other goodness that those kernels have?  We don't normally
> > > backport new features, right?
> >
> > I think this should be considered as a fix, not a new feature.
> >
> > MANA is designed to be 200GB full duplex at the start.  Due to lack of
> > hardware testing capability at early stage of the project, we could
> > only test 100GB for the Linux driver. When hardware is fully capable
> > of reaching designed spec, this bug in the Linux driver shows up.
>=20
> That part we understand.
>=20
> If I were you I'd try to convince Greg and Paolo that the change is small=
 and
> significant for user experience. And answer Greg's question why upgrading=
 the
> kernel past 6.1 is a challenge in your environment.

I was under the impression that this patch was considered to be a feature,=
=20
not a bug fix. I was trying to justify that the "Fixes:" tag was needed.=20

I apologize for misunderstanding this.

Without this fix, it's not possible to run a typical workload designed for =
200Gb
physical link speed.

We see a large number of customers and Linux distributions committed on 5.1=
5=20
and 6.1 kernels. They planned the product cycles and certification processe=
s=20
around these longterm kernel versions. It's difficult for them to upgrade t=
o newer
kernel versions.

Thanks,

Long