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: <4db44c27-4654-46f9-be41-93bcf06302b2@redhat.com>
Date: Tue, 13 Jan 2026 11:27:47 +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>,
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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 1/9/26 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...

/P