On Sun, 2023-07-02 at 20:18 +0000, Long Li wrote:

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Subject: Re: [Patch v3] net: mana: Batch ringing RX
queue
doorbell
on receiving
packets

On Fri, 30 Jun 2023 20:42:28 +0000 Long Li wrote:

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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.

That part we understand.

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, 
not a bug fix. I was trying to justify that the "Fixes:" tag
was
needed. 

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 5.15 
and 6.1 kernels. They planned the product cycles and
certification
processes 
around these longterm kernel versions. It's difficult for them
to
upgrade to newer
kernel versions.

I think there are some misunderstanding WRT distros and stable kernels.
(Commercial) distros will backport the patch as needed, regardless such
patch landing in the 5.15 upstream tree or not. Individual users
running their own vanilla 5.15 kernel can't expect performance
improvement landing there.

All in all I feel undecided. I would endorse this change going trough
net-next (without the stable tag). I would feel less torn with this
change targeting -net without the stable tag. Targeting -net with the
stable tag sounds a bit too much to me.

Cheers,
Paolo