From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: david laight <david.laight@runbox.com>
Cc: <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
<tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
<dave.hansen@linux.intel.com>
Subject: Re: [RFC PATCH 3/3] x86/lib: Use EGPRs in 64-bit checksum copy loop
Date: Mon, 1 Dec 2025 13:39:31 -0800 [thread overview]
Message-ID: <0fef00d6-b7f9-47aa-8f4d-1b4c6c4ebb3f@intel.com> (raw)
In-Reply-To: <20251125103750.2d2d7bbd@pumpkin>
On 11/25/2025 2:37 AM, david laight wrote:
>
> This code (or something very similar) gets used to checksum data
> during copy_to/from_user for sockets.
> This goes back a long way and I suspect the 'killer ap' was nfsd
> running over UDP (with 8k+ UDP datagrams).
> Modern NICs all (well all anyone cares about) to IP checksum offload.
> So you don't need to checksum on send() - I'm sure that is still
> enabled even though you pretty much never want it.
> The checksum on recv() can only happen for UDP, but massively
> complicates the code paths and will normally not be needed.
It sounds like this optimization wouldn't provide practical benefit. I
don't see a strong case for pursuing this further either, so I'd drop this.
Thanks,
Chang
next prev parent reply other threads:[~2025-12-01 21:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-24 21:32 [DISCUSSION] x86: In-Kernel Use of Extended General-Purpose Registers Chang S. Bae
2025-11-24 21:32 ` [RFC PATCH 1/3] x86/lib: Refactor csum_partial_copy_generic() into a macro Chang S. Bae
2025-11-24 21:32 ` [RFC PATCH 2/3] x86/lib: Convert repeated asm sequences in checksum copy into macros Chang S. Bae
2025-11-24 21:32 ` [RFC PATCH 3/3] x86/lib: Use EGPRs in 64-bit checksum copy loop Chang S. Bae
2025-11-25 10:37 ` david laight
2025-12-01 21:39 ` Chang S. Bae [this message]
2025-11-26 16:30 ` [DISCUSSION] x86: In-Kernel Use of Extended General-Purpose Registers Peter Zijlstra
2025-12-01 21:40 ` Chang S. Bae
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