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

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Message-ID: <20230630163805.79c0bdf5@kernel.org>
Date:   Fri, 30 Jun 2023 16:38:05 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Long Li <longli@...rosoft.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "longli@...uxonhyperv.com" <longli@...uxonhyperv.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        Ajay Sharma <sharmaajay@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
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:
> > > 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.