RE: [PATCH rtw-next] wifi: rtw89: usb: shorten the RX aggregation hold on RTL8922AU

[Ping-Ke Shih <pkshih@realtek.com>]

Devin Wittmayer <lucid_duck@justthetip.ca> wrote:
> The RTL8922AU holds received frames for up to a millisecond before
> handing them to the host, a value carried over from the RTL8852CU.
> That adds up to a millisecond of round trip, and under load at 160 MHz
> the access point drops to lower rates and download suffers.
> 
> Shorten the hold on this chip. Upload is unchanged, and so is download
> on a USB 2 port, where the bus is the limit. 

Can I know the number of USB 2 port? Just curious, not blocking item.

> The cost is some extra CPU at the same load.

I think the major reason people want RX aggregation is that a chip is
operating on a low-end CPU. 

> 
> RTL8922AU on USB 3 at 160 MHz, power save off for the round trip:
> 
>                          x86, 6 GHz    x86, 5 GHz    Pi 5, 6 GHz
>                         before after  before after  before after
>   TCP down, 1 flow        613  1002     579   948     586   999  Mbps
>   TCP down, 8 flows       656  1187     629  1080     605  1108  Mbps
>   round trip             2.33  1.29    2.25  1.18    1.44  0.88  ms
>   busiest core, UDP 200M  8.4  12.8     8.3  12.9     2.3   2.8  %
> 
> Fixes: 32cee8a9bb66 ("wifi: rtw89: usb: Enable RX aggregation for RTL8922AU")
> Reported-by: Nick Morrow <morrownr@gmail.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Devin Wittmayer <lucid_duck@justthetip.ca>

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

> ---
> Ping-Ke, Bitterblue pointed me to you, since the 32 came from Realtek.
> Realtek's 8852CU driver uses it as the default and also has a
> small-packet mode that sets the hold to 1, the value this patch uses.
> If the longer default is there for a reason these tests would miss,
> please let me know, thank you.

I can't find small-packet mode you mentioned, please share a link. 

As I know the reason of longer default can benefit low-end CPU. 
By the way, the TX aggregation is pending, because our experiments
show no gain after the patch, so I don't send the patch. That means
current platform is much better than what years ago.

Ping-Ke