netdev - Re: [PATCH net-next v4 1/4] net: ethtool: support including Flow Label in the flow hash for RSS

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Message-ID: <aJqKVHT3v-4Pc1hC@MacBook-Air.local>
Date: Mon, 11 Aug 2025 17:27:00 -0700
From: Joe Damato <joe@...a.to>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
	pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
	donald.hunter@...il.com, michael.chan@...adcom.com,
	pavan.chebbi@...adcom.com, willemdebruijn.kernel@...il.com,
	ecree.xilinx@...il.com, andrew@...n.ch
Subject: Re: [PATCH net-next v4 1/4] net: ethtool: support including Flow
 Label in the flow hash for RSS

On Mon, Aug 11, 2025 at 04:42:09PM -0700, Jakub Kicinski wrote:
> Some modern NICs support including the IPv6 Flow Label in
> the flow hash for RSS queue selection. This is outside
> the old "Microsoft spec", but was included in the OCP NIC spec:
> 
>   [ ] RSS include ow label in the hash (configurable)
                   ^^^ flow?
 
[...]

> Due to the nature of host processing (relatively long queues,
> other kernel subsystems masking IRQs for 100s of msecs)
> the risk of reordering within the host is higher than in
> the network. But for applications which need it - it is far
> preferable to potentially persistent overload of subset of
                          ^^^^^^^^^^^^ maybe a typo of some kind or I'm just
                          reading it wrong, but can't seem to follow this
                          sentence?

> queues.

[...]
 
> ---
> CC: andrew@...n.ch
> CC: ecree.xilinx@...il.com
> ---
>  Documentation/netlink/specs/ethtool.yaml |  3 +++
>  include/uapi/linux/ethtool.h             |  1 +
>  net/ethtool/ioctl.c                      | 25 ++++++++++++++++++++++
>  net/ethtool/rss.c                        | 27 ++++++++++++------------
>  4 files changed, 43 insertions(+), 13 deletions(-)

Commit message nits aside, this is really interesting work.

Reviewed-by: Joe Damato <joe@...a.to>