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

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Date:   Sat, 19 Dec 2020 16:18:40 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>,
        Ben Greear <greearb@...delatech.com>,
        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 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.

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)?

johannes