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

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Message-ID: <0eab9112-eedf-4425-9ce9-be0a59191d8d@redhat.com>
Date: Tue, 13 Jan 2026 11:41:27 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Pavel Begunkov <asml.silence@...il.com>, netdev@...r.kernel.org
Cc: "David S . Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Jonathan Corbet <corbet@....net>, Michael Chan <michael.chan@...adcom.com>,
 Pavan Chebbi <pavan.chebbi@...adcom.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Joshua Washington <joshwash@...gle.com>,
 Harshitha Ramamurthy <hramamurthy@...gle.com>,
 Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>,
 Mark Bloch <mbloch@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 Alexander Duyck <alexanderduyck@...com>,
 Ilias Apalodimas <ilias.apalodimas@...aro.org>, Shuah Khan
 <shuah@...nel.org>, Willem de Bruijn <willemb@...gle.com>,
 Ankit Garg <nktgrg@...gle.com>, Tim Hostetler <thostet@...gle.com>,
 Alok Tiwari <alok.a.tiwari@...cle.com>, Ziwei Xiao <ziweixiao@...gle.com>,
 John Fraker <jfraker@...gle.com>,
 Praveen Kaligineedi <pkaligineedi@...gle.com>,
 Mohsin Bashir <mohsin.bashr@...il.com>, Joe Damato <joe@...a.to>,
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Subject: Re: [PATCH net-next v8 6/9] eth: bnxt: adjust the fill level of agg
 queues with larger buffers

On 1/13/26 11:27 AM, Paolo Abeni wrote:
> On 1/9/26 12:28 PM, Pavel Begunkov wrote:
>> From: Jakub Kicinski <kuba@...nel.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@...nel.org>
>> [pavel: rebase on top of agg_size_fac, assert agg_size_fac]
>> Signed-off-by: Pavel Begunkov <asml.silence@...il.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 see the next patch rejects too small `rx_page_size` values; so
possibly the better option is to drop the confusing check in
bnxt_alloc_rx_page_pool().

/P