Subject: Re: [PATCH] arm64: remove HAVE_CMPXCHG_LOCAL

From: Shakeel Butt <[email-masked]>
Date: Wed, 18 Feb 2026 14:07:57 -0800

On Sun, Feb 15, 2026 at 11:39:44AM +0800, Jisheng Zhang wrote:
> It turns out the generic disable/enable irq this_cpu_cmpxchg
> implementation is faster than LL/SC or lse implementation. Remove
> HAVE_CMPXCHG_LOCAL for better performance on arm64.
> 
> Tested on Quad 1.9GHZ CA55 platform:
> average mod_node_page_state() cost decreases from 167ns to 103ns
> the spawn (30 duration) benchmark in unixbench is improved
> from 147494 lps to 150561 lps, improved by 2.1%
> 
> Tested on Quad 2.1GHZ CA73 platform:
> average mod_node_page_state() cost decreases from 113ns to 85ns
> the spawn (30 duration) benchmark in unixbench is improved
> from 209844 lps to 212581 lps, improved by 1.3%
> 
> Signed-off-by: Jisheng Zhang <[email-masked]>

Please note that mod_node_page_state() can be called in NMI context and
generic disable/enable irq are not safe against NMIs (newer arm arch supports
NMI).