netdev - Re: [PATCH net-next 0/4] tun: optimize SKB allocation with NAPI cache

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Message-ID: <681a22ac9964d_15abb629445@willemb.c.googlers.com.notmuch>
Date: Tue, 06 May 2025 10:54:36 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jon Kohler <jon@...anix.com>, 
 ast@...nel.org, 
 daniel@...earbox.net, 
 davem@...emloft.net, 
 kuba@...nel.org, 
 hawk@...nel.org, 
 john.fastabend@...il.com, 
 netdev@...r.kernel.org, 
 bpf@...r.kernel.org, 
 jon@...anix.com, 
 aleksander.lobakin@...el.com
Subject: Re: [PATCH net-next 0/4] tun: optimize SKB allocation with NAPI cache

Jon Kohler wrote:
> Use the per-CPU NAPI cache for SKB allocation, leveraging bulk
> allocation since the batch size is known at submission time. This
> improves efficiency by reducing allocation overhead, particularly when
> using IFF_NAPI and GRO, which can replenish the cache in a tight loop.

Do you have experimental data?
 
> Additionally, utilize napi_build_skb and napi_consume_skb to further
> benefit from the NAPI cache.
> 
> Note: This series does not address the large payload path in
> tun_alloc_skb, which spans sock.c and skbuff.c. A separate series will
> handle privatizing the allocation code in tun and integrating the NAPI
> cache for that path.
> 
> Thanks all,
> Jon
> 
> Jon Kohler (4):
>   tun: rcu_deference xdp_prog only once per batch
>   tun: optimize skb allocation in tun_xdp_one
>   tun: use napi_build_skb in __tun_build_skb
>   tun: use napi_consume_skb in tun_do_read
> 
>  drivers/net/tun.c | 60 +++++++++++++++++++++++++++++++++--------------
>  1 file changed, 42 insertions(+), 18 deletions(-)
> 
> -- 
> 2.43.0
>