Re: [PATCH 1/2] usb: dwc2: Fix DMA alignment to start at allocated boundary

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On 6 July 2018 at 18:57, Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
> Hi,
>
> Thanks for tracking this down and sorry for the original regression.
> Seems like a good fix.  With this fix, I'd be curious of your
> observations on how dwc2 performs (both performance and compatibility
> under stress) with the newest driver compared to whatever you were
> using before.
>

My totally not scientifically accurate performance test included
running iperf through my LTE dongle that was connected to dwc2. I saw
throughput increase in download speeds.

Before (kernel 4.9.109 with the offending commit reverted) iperf
reported download bandwidth at 33.2 Mbits/sec

Using newest dwc2 driver after applying "Fix DMA alignment to start at
allocated boundary" patch I got 38.2 Mbits/sec

If I also apply the "Fix inefficient copy of unaligned buffers" patch
I could achieve a total throughput for download around 44.6 Mbits/sec
which I believe is capped by my 50Mbit/s subscription.

> Also: you're using the dwc2_set_ltq_params() parameters?  Have you
> checked if removing the "max_transfer_size" limit boosts your
> performance?
>

Yes, I'm using the parameters set there. I tried removing
max_transfer_size but it did not have noticeable impact on the
performance in my tests.

> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>

Thanks for reviewing :)

-Antti
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