Re: [PATCH net-next v8 6/9] eth: bnxt: adjust the fill level of agg queues with larger buffers

[Pavel Begunkov <asml.silence@gmail.com>]

On 1/13/26 10:27, Paolo Abeni wrote:
> On 1/9/26 12:28 PM, Pavel Begunkov wrote:
>> From: Jakub Kicinski <kuba@kernel.org>
>>
>> The driver tries to provision more agg buffers than header buffers
>> since multiple agg segments can reuse the same header. The calculation
>> / heuristic tries to provide enough pages for 65k of data for each header
>> (or 4 frags per header if the result is too big). This calculation is
>> currently global to the adapter. If we increase the buffer sizes 8x
>> we don't want 8x the amount of memory sitting on the rings.
>> Luckily we don't have to fill the rings completely, adjust
>> the fill level dynamically in case particular queue has buffers
>> larger than the global size.
>>
>> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
>> [pavel: rebase on top of agg_size_fac, assert agg_size_fac]
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>>   drivers/net/ethernet/broadcom/bnxt/bnxt.c | 28 +++++++++++++++++++----
>>   1 file changed, 24 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> index 8f42885a7c86..137e348d2b9c 100644
>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
>> @@ -3816,16 +3816,34 @@ static void bnxt_free_rx_rings(struct bnxt *bp)
>>   	}
>>   }
>>   
>> +static int bnxt_rx_agg_ring_fill_level(struct bnxt *bp,
>> +				       struct bnxt_rx_ring_info *rxr)
>> +{
>> +	/* User may have chosen larger than default rx_page_size,
>> +	 * we keep the ring sizes uniform and also want uniform amount
>> +	 * of bytes consumed per ring, so cap how much of the rings we fill.
>> +	 */
>> +	int fill_level = bp->rx_agg_ring_size;
>> +
>> +	if (rxr->rx_page_size > BNXT_RX_PAGE_SIZE)
>> +		fill_level /= rxr->rx_page_size / BNXT_RX_PAGE_SIZE;
> 
> According to the check in bnxt_alloc_rx_page_pool() it's theoretically
> possible for `rxr->rx_page_size / BNXT_RX_PAGE_SIZE` being zero. If so
> the above would crash.
> 
> Side note: this looks like something AI review could/should catch. The
> fact it didn't makes me think I'm missing something...

I doubt LLMs will be able to see it, but rx_page_size is no less
than BNXT_RX_PAGE_SIZE. It's either set from defaults, which is
exactly BNXT_RX_PAGE_SIZE, or given by the provider and then
checked in bnxt_validate_qcfg().

-- 
Pavel Begunkov