From: David Laight <david.laight.linux@gmail.com>
To: Wei Fang <wei.fang@nxp.com>
Cc: shenwei.wang@nxp.com, xiaoning.wang@nxp.com, frank.li@nxp.com,
andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, ast@kernel.org,
daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
sdf@fomichev.me, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, imx@lists.linux.dev,
bpf@vger.kernel.org
Subject: Re: [PATCH net-next 07/11] net: fec: use switch statement to check the type of tx_buf
Date: Wed, 14 Jan 2026 13:47:13 +0000 [thread overview]
Message-ID: <20260114134713.565f2b3c@pumpkin> (raw)
In-Reply-To: <20260113032939.3705137-8-wei.fang@nxp.com>
On Tue, 13 Jan 2026 11:29:35 +0800
Wei Fang <wei.fang@nxp.com> wrote:
> The tx_buf has three types: FEC_TXBUF_T_SKB, FEC_TXBUF_T_XDP_NDO and
> FEC_TXBUF_T_XDP_TX. Currently, the driver uses 'if...else...' statements
> to check the type and perform the corresponding processing. This is very
> detrimental to future expansion. For example, if new types are added to
> support XDP zero copy in the future, continuing to use 'if...else...'
> would be a very bad coding style. So the 'if...else...' statements in
> the current driver are replaced with switch statements to support XDP
> zero copy in the future.
The if...else... sequence has the advantage that the common 'cases'
can be put first.
The compiler will use a branch tree for a switch statement (jumps tables
are pretty much not allowed because of speculative execution issues) and
limit the maximum number of branches.
That is likely to be pessimal in many cases - especially if it generates
mispredicted branches for the common cases.
So not clear cut at all.
David
next prev parent reply other threads:[~2026-01-14 13:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-13 3:29 [PATCH net-next 00/11] net: fec: improve XDP copy mode and add AF_XDP zero-copy support Wei Fang
2026-01-13 3:29 ` [PATCH net-next 01/11] net: fec: add fec_txq_trigger_xmit() helper Wei Fang
2026-01-13 15:52 ` Frank Li
2026-01-13 3:29 ` [PATCH net-next 02/11] net: fec: add fec_rx_error_check() to check RX errors Wei Fang
2026-01-13 15:53 ` Frank Li
2026-01-13 3:29 ` [PATCH net-next 03/11] net: fec: add rx_shift to indicate the extra bytes padded in front of RX frame Wei Fang
2026-01-13 15:56 ` Frank Li
2026-01-13 3:29 ` [PATCH net-next 04/11] net: fec: add fec_build_skb() to build a skb Wei Fang
2026-01-13 15:59 ` Frank Li
2026-01-14 2:32 ` Wei Fang
2026-01-13 3:29 ` [PATCH net-next 05/11] net: fec: add fec_enet_rx_queue_xdp() for XDP path Wei Fang
2026-01-13 16:11 ` Frank Li
2026-01-13 3:29 ` [PATCH net-next 06/11] net: fec: transmit XDP frames in bulk Wei Fang
2026-01-13 16:17 ` Frank Li
2026-01-14 9:57 ` Wei Fang
2026-01-13 3:29 ` [PATCH net-next 07/11] net: fec: use switch statement to check the type of tx_buf Wei Fang
2026-01-13 16:22 ` Frank Li
2026-01-14 10:01 ` Wei Fang
2026-01-14 13:47 ` David Laight [this message]
2026-01-15 2:27 ` Wei Fang
2026-01-13 3:29 ` [PATCH net-next 08/11] net: fec: remove the size parameter from fec_enet_create_page_pool() Wei Fang
2026-01-13 3:29 ` [PATCH net-next 09/11] net: fec: move xdp_rxq_info* APIs out of fec_enet_create_page_pool() Wei Fang
2026-01-13 3:29 ` [PATCH net-next 10/11] net: fec: add fec_alloc_rxq_buffers_pp() to allocate buffers from page pool Wei Fang
2026-01-13 3:29 ` [PATCH net-next 11/11] net: fec: add AF_XDP zero-copy support Wei Fang
2026-01-13 9:29 ` kernel test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260114134713.565f2b3c@pumpkin \
--to=david.laight.linux@gmail.com \
--cc=andrew+netdev@lunn.ch \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=frank.li@nxp.com \
--cc=hawk@kernel.org \
--cc=imx@lists.linux.dev \
--cc=john.fastabend@gmail.com \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=sdf@fomichev.me \
--cc=shenwei.wang@nxp.com \
--cc=wei.fang@nxp.com \
--cc=xiaoning.wang@nxp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox