netdev - Re: [PATCH v24 01/20] net: Introduce direct data placement tcp offload

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Message-ID: <253o79wr3lh.fsf@mtr-vdi-124.i-did-not-set--mail-host-address--so-tickle-me>
Date: Fri, 26 Apr 2024 10:21:46 +0300
From: Aurelien Aptel <aaptel@...dia.com>
To: Sagi Grimberg <sagi@...mberg.me>, linux-nvme@...ts.infradead.org,
 netdev@...r.kernel.org, hch@....de, kbusch@...nel.org, axboe@...com,
 chaitanyak@...dia.com, davem@...emloft.net, kuba@...nel.org
Cc: Boris Pismenny <borisp@...dia.com>, aurelien.aptel@...il.com,
 smalin@...dia.com, malin1024@...il.com, ogerlitz@...dia.com,
 yorayz@...dia.com, galshalom@...dia.com, mgurtovoy@...dia.com,
 edumazet@...gle.com, pabeni@...hat.com, dsahern@...nel.org,
 ast@...nel.org, jacob.e.keller@...el.com
Subject: Re: [PATCH v24 01/20] net: Introduce direct data placement tcp offload

Hi Sagi,

Sagi Grimberg <sagi@...mberg.me> writes:
>> +     config->io_cpu = sk->sk_incoming_cpu;
>> +     ret = netdev->netdev_ops->ulp_ddp_ops->sk_add(netdev, sk, config);
>
> Still don't understand why you need the io_cpu config if you are passing
> the sk to the driver...

With our HW we cannot move the offload queues to a different CPU without
destroying and recreating the offload resources on the new CPU.

Since the connection is created from a different CPU then the io queue
thread, we cannot predict which CPU we should create our offload context
on.

Ideally, io_cpu should be set to nvme_queue->io_cpu or it should be removed
and the socket should be offloaded from the io thread. What do you
prefer?

Thanks