netdev - Re: [PATCH v1 net-next 02/15] net: Introduce direct data placement tcp offload

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Message-ID: <20201211230515.n5i2i2w23zdwnl6q@bsd-mbp.dhcp.thefacebook.com>
Date:   Fri, 11 Dec 2020 15:05:15 -0800
From:   Jonathan Lemon <jonathan.lemon@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Boris Pismenny <borispismenny@...il.com>,
        Boris Pismenny <borisp@...lanox.com>, davem@...emloft.net,
        saeedm@...dia.com, hch@....de, sagi@...mberg.me, axboe@...com,
        kbusch@...nel.org, viro@...iv.linux.org.uk, edumazet@...gle.com,
        boris.pismenny@...il.com, linux-nvme@...ts.infradead.org,
        netdev@...r.kernel.org, benishay@...dia.com, ogerlitz@...dia.com,
        yorayz@...dia.com, Ben Ben-Ishay <benishay@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Yoray Zack <yorayz@...lanox.com>,
        Boris Pismenny <borisp@...dia.com>
Subject: Re: [PATCH v1 net-next 02/15] net: Introduce direct data placement
 tcp offload

On Fri, Dec 11, 2020 at 12:59:52PM -0700, David Ahern wrote:
> On 12/11/20 11:45 AM, Jakub Kicinski wrote:
> > Ack, these patches are not exciting (to me), so I'm wondering if there
> > is a better way. The only reason NIC would have to understand a ULP for
> > ZC is to parse out header/message lengths. There's gotta be a way to
> > pass those in header options or such...
> > 
> > And, you know, if we figure something out - maybe we stand a chance
> > against having 4 different zero copy implementations (this, TCP,
> > AF_XDP, netgpu) :(
> 
> AF_XDP is for userspace IP/TCP/packet handling.
> 
> netgpu is fundamentally kernel stack socket with zerocopy direct to
> userspace buffers. Yes, it has more complications like the process is
> running on a GPU, but essential characteristics are header / payload
> split, a kernel stack managed socket, and dedicated H/W queues for the
> socket and those are all common to what the nvme patches are doing. So,
> can we create a common framework for those characteristics which enables
> other use cases (like a more generic Rx zerocopy)?

AF_XDP could also be viewed as a special case of netgpu.
-- 
Jonathan