On 31.07.20 01:37, Jakub Kicinski wrote:

On Thu, 30 Jul 2020 17:01:21 +0200 Julian Wiedmann wrote:

quoted

The (misplaced) comment doesn't make any sense, enforcing an
uninitialized RX buffer won't help with IRQ reduction.

So make the best use of all available RX buffers.

Often one entry in the ring is left free to make it easy to
differentiate between empty and full conditions. 

Is this not the reason here?

Hmm no, the HW architecture works slightly different.

There's no index register that we could query for HW progress,
each ring entry has an associated state byte that needs to be
inspected and indicates HW progress (among other things).

So this was more likely just a mis-interpretation of how the
(quirky) IRQ reduction mechanism works in HW, or maybe part of
a code path that got removed during the NAPI conversion.