netdev - Re: net: tso: add UDP segmentation support: adds regression for ax200 upload

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Date:   Sat, 19 Dec 2020 08:55:05 -0800
From:   Ben Greear <greearb@...delatech.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Luca Coelho <luciano.coelho@...el.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>, linux-wireless@...r.kernel.org
Subject: Re: net: tso: add UDP segmentation support: adds regression for ax200
 upload

On 12/19/20 7:18 AM, Johannes Berg wrote:
> On Fri, 2020-12-18 at 12:16 -0800, Jakub Kicinski wrote:
>> On Thu, 17 Dec 2020 12:40:26 -0800 Ben Greear wrote:
>>> On 12/17/20 10:20 AM, Eric Dumazet wrote:
>>>> On Thu, Dec 17, 2020 at 7:13 PM Ben Greear <greearb@...delatech.com> wrote:
>>>>> It is the iwlwifi/mvm logic that supports ax200.
>>>>
>>>> Let me ask again :
>>>>
>>>> I see two different potential call points :
>>>>
>>>> drivers/net/wireless/intel/iwlwifi/pcie/tx.c:1529:
>>>> tso_build_hdr(skb, hdr_page->pos, &tso, data_left, !total_len);
>>>> drivers/net/wireless/intel/iwlwifi/queue/tx.c:427:
>>>> tso_build_hdr(skb, hdr_page->pos, &tso, data_left, !total_len);
>>>>
>>>> To the best of your knowledge, which one would be used in your case ?
>>>>
>>>> Both are horribly complex, I do not want to spend time studying two
>>>> implementations.
>>>
>>> It is the queue/tx.c code that executes on my system, verified with
>>> printk.
>>
>> Not sure why Intel's not on CC here.
> 
> Heh :)
> 
> Let's also add linux-wireless.
> 
>> Luca, is the ax200 TSO performance regression with recent kernel on your
>> radar?
> 
> It wasn't on mine for sure, so far. But it's supposed to be Christmas
> vacation, so haven't checked our bug tracker etc. I see Emmanuel was at
> least looking at the bug report, but not sure what else happened yet.

Not to bitch and moan too much, but even the most basic of testing would
have shown this, how can testing be so poor on the ax200 driver?

It even shows up with the out-of-tree ax200 driver.

> Off the top of my head, I don't really see the issue. Does anyone have
> the ability to capture the frames over the air (e.g. with another AX200
> in monitor mode, load the driver with amsdu_size=3 module parameter to
> properly capture A-MSDUs)?

I can do that at some point, and likely it could be reproduced with an /n or /ac
AP and those are a lot easier to sniff.

Thanks,
Ben


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com