From: Jesper Dangaard Brouer <hawk@kernel.org>
To: Tianyi Gao <tianyi@cloudflare.com>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: netdev@vger.kernel.org, "Jakub Kicinski" <kuba@kernel.org>,
"Paolo Abeni" <pabeni@redhat.com>,
"Eric Dumazet" <edumazet@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Simon Horman" <horms@kernel.org>,
"David Keogh" <dkeogh@amazon.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"David Woodhouse" <dwmw2@infradead.org>,
"Dragos Tatulea" <dtatulea@nvidia.com>,
"Nimrod Oren" <noren@nvidia.com>,
"Alasdair McWilliam" <alasdair@mcwilliam.dev>,
"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
"Stanislav Fomichev" <sdf@fomichev.me>,
"Magnus Karlsson" <magnus.karlsson@intel.com>,
"David Ahern" <dsahern@kernel.org>,
"Ido Schimmel" <idosch@nvidia.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"John Fastabend" <john.fastabend@gmail.com>,
"Donald Hunter" <donald.hunter@gmail.com>,
"Andrew Lunn" <andrew+netdev@lunn.ch>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <skhan@linuxfoundation.org>,
"Shuah Khan" <shuah@kernel.org>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Breno Leitao" <leitao@debian.org>,
"Asbjørn Sloth Tønnesen" <ast@fiberby.net>,
"Danielle Ratson" <danieller@nvidia.com>,
"Kuniyuki Iwashima" <kuniyu@google.com>,
bpf@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kselftest@vger.kernel.org, kernel-team@cloudflare.com,
nh-open-source@amazon.com
Subject: Re: [PATCH net-next 1/8] net: add tx_extra_headroom and LL_ALLOC_SPACE()
Date: Tue, 10 Nov 2026 15:48:26 +0100 [thread overview]
Message-ID: <afe441ca-d616-4132-ae68-95d3ae5e111f@kernel.org> (raw)
In-Reply-To: <20261108214356.95406-1-tianyi@cloudflare.com>
On 11/8/26 22:43, Tianyi Gao wrote:
> - That growth can move skbs into a larger kmalloc size without anyone
> deciding it. On x86_64, for 1500-byte MTU UDP over IPv4 on an
> Ethernet device, 194 bytes or more moves the skb head from
> kmalloc-2048 to kmalloc-4096. That adds 2048 bytes to the memory and
> the truesize of each such skb. The IFLA_TX_EXTRA_HEADROOM UAPI can
> do the same, but then the operator chose to pay that cost.
This reminds me that I have previously proposed changing both the
generic XDP and veth headroom check to use 192 bytes instead of 256
bytes. This makes sense because Intel driver for native XDP already set
this to 192 bytes. Exactly due to 1500 MTU packets will fit into a 2048
alignment. e.g. 2048 -192 -320 (shared_info) = 1536 bytes left.
Reading about, this would also translate into a performance benefit?
--Jesper
next prev parent reply other threads:[~2026-11-10 14:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-07 3:34 [PATCH net-next 0/8] net: configurable extra TX headroom for local egress Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 1/8] net: add tx_extra_headroom and LL_ALLOC_SPACE() Tianyi Gao
2026-11-07 14:51 ` Willem de Bruijn
2026-11-07 18:25 ` Tianyi Gao
2026-11-08 15:13 ` Willem de Bruijn
2026-11-08 21:43 ` Tianyi Gao
2026-11-10 14:48 ` Jesper Dangaard Brouer [this message]
2026-11-09 3:08 ` Stephen Hemminger
2026-11-09 15:49 ` Tianyi Gao
2026-11-10 16:23 ` Willem de Bruijn
2026-11-10 20:12 ` Tianyi Gao
2026-11-11 3:27 ` Willem de Bruijn
2026-11-11 20:23 ` David Keogh
2026-11-11 20:37 ` David Keogh
2026-11-11 21:41 ` Tianyi Gao
2026-11-11 23:19 ` David Keogh
2026-11-12 0:03 ` Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 2/8] net: reserve extra TX headroom for local egress Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 3/8] rtnetlink: add IFLA_TX_EXTRA_HEADROOM Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 4/8] selftests: net: add tx_extra_headroom test Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 5/8] selftests: net: tx_extra_headroom: test a push at TC egress Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 6/8] selftests: net: add flag to send a frame in xdp_helper Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 7/8] selftests: net: tx_extra_headroom: test generic XDP on the veth peer Tianyi Gao
2026-11-07 3:34 ` [PATCH net-next 8/8] selftests: net: tx_extra_headroom: test veth peer at creation Tianyi Gao
2026-11-10 15:38 ` Jakub Kicinski
2026-11-10 15:45 ` Tianyi Gao
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