Re: brcmfmac experiment for a specific use case - tx throughput maximization for slow CPU with glomming

["Jörg Krause" <joerg.krause@embedded.rocks>]

Hi Jérôme,

On Wed, 2017-05-24 at 07:33 -0400, Jérôme Carretero wrote:
> Hi,
> 
> 
> I've crippled a Raspberry Pi 3 (1 core, 200 MHz) and observed that the
> glomming feature has a definite impact on TX performance, but it looks
> like at this CPU frequency, the work queue is solicited "too often"
> by brcmf_sdio_trigger_dpc() and glomming is only doing 4 packets at
> once, resulting in maybe a sub-optimal throughput.

I'm experiencing low throughput with a BCM43362 wifi chip attached via
SDIO to an i.MX28 [1,2]. After disabling some Kernel debug features I'm
getting now a TCP throughput of 12.5 Mbps for the wifi interface, which
is still below the throughput I get for the Cubietruck.

> 
> I have a vague idea that deliberately delaying the transmissions so as
> to wait for either a small timeout, or the glomming level has been
> reached, would be something worth exploring.
> But I haven't spent a long time looking at the driver.

If you are in need for any testing I'm willing to help!

[1] https://www.spinics.net/lists/linux-wireless/msg153257.html	
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-October/
461137.html

Jörg