netdev - Re: [PATCH net-next] etherdevice: Optimize is_broadcast_ether

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Message-ID: <20240613170522.0961c781@kernel.org>
Date: Thu, 13 Jun 2024 17:05:22 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Qingfang Deng <dqfext@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Joe Perches
 <joe@...ches.com>, Qingfang Deng <qingfang.deng@...lower.com.cn>
Subject: Re: [PATCH net-next] etherdevice: Optimize is_broadcast_ether_addr

On Thu, 13 Jun 2024 15:34:41 +0800 Qingfang Deng wrote:
> Like is_zero_ether_addr, is_broadcast_ether_addr can also be optimized
> by using a 32-bit load if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.
> Sign extension is used to populate the upper 16-bit of the 16-bit load.

Can you provide more context on why it's beneficial. I mean, there's a
lot of code in the kernel one could micro-optimize...

Show us the assembly, cycle counts, where it's used on fast paths...
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