On Wed, 2020-09-16 at 18:46 +0200, Felix Fietkau wrote:
> Some APs (e.g. Asus RT-AC88U) have been observed to report an HT MSDU size
> limit of 3839 and a VHT limit of 7991. These APs can handle bigger frames
> than 3839 bytes just fine, so we should remove the VHT limit based on the
> HT capabilities. This improves tx throughput.
I'm not really convinced that we can do this, since we don't track
HT/VHT limits separately.
IOW, to be behaving according to the AP you mention, we'd have to know
when building an A-MSDU whether it's going to use HT or VHT rates, but
we don't track that at all ...
johannes
On 2020-09-16 19:44, Johannes Berg wrote:
> On Wed, 2020-09-16 at 18:46 +0200, Felix Fietkau wrote:
>> Some APs (e.g. Asus RT-AC88U) have been observed to report an HT MSDU size
>> limit of 3839 and a VHT limit of 7991. These APs can handle bigger frames
>> than 3839 bytes just fine, so we should remove the VHT limit based on the
>> HT capabilities. This improves tx throughput.
>
> I'm not really convinced that we can do this, since we don't track
> HT/VHT limits separately.
>
> IOW, to be behaving according to the AP you mention, we'd have to know
> when building an A-MSDU whether it's going to use HT or VHT rates, but
> we don't track that at all ...
These comments don't make sense to me. A-MSDU limit is tracked per sta,
and on all the implementations I've looked at, HT rates are never used
to transmit to a peer that can do VHT. It would be unnecessary to do
that anyway, since VHT modulations are a superset of HT modulations with
just some header differences.
On another note, VHT already supports bigger A-MSDU limits than HT in
the code below that check.
- Felix