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b=pdcz32uZUn9hgWq5Qk5Iruwxvu9Zmrvzsq+r/JIlJLbneE8xoBTfr4aj6UZoS1ymu EXpOXsFcYyvGEXZWH5XGJugsQmslOztNOyJ/T9qZEzKUX6pjCms1Qk0+gl/BLDfwei FOHVHRbdxNWXqKbA219UQKpQfGTvz6zHcp5Hu8WroHijRa7+DL76tCbDzHzR3kJPpy mYg50NjO3nhBjMzz2QQ3wjol4L73oHB2zaB3Xk8Srhh3k2u1vWuSWgr6W1f564Z41o jgK5yOOXhY7ccMRm6oiAEQDFLMX7g7hxIBdUtLrd/FCNNMYzDUVFJVzbH7KEFWnRKx ks9+0uyPSkoUQ== Date: Mon, 16 Feb 2026 11:00:59 +0000 From: Will Deacon To: Jisheng Zhang Cc: Catalin Marinas , Dennis Zhou , Tejun Heo , Christoph Lameter , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, maz@kernel.org Subject: Re: [PATCH] arm64: remove HAVE_CMPXCHG_LOCAL Message-ID: References: <20260215033944.16374-1-jszhang@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260215033944.16374-1-jszhang@kernel.org> X-Rspamd-Queue-Id: A87C240005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: giyixkoa96txjq4sinbhtcx51hiuyhrm X-HE-Tag: 1771239665-455470 X-HE-Meta: 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 FfrcL1w3 jj5S+1naxvhrRORWi65yyD+uY2hkyT0UIUos1Y/U2UuheKjJUPP0YzJ6tmSGWurkGC7P7TdMBoaFBAnPrPc8EZ4leRVzhIjyc5ybr3gZiR/Qs7l+iUsJgHeV/S7MVpufKaa+7rCW2B4kMoL9KURpRhhQTFKZyQ6xCXi5Wzaohe6Mwuzc/TZeGMR0X4ZudYARCXfDY8u0rxlJuUWXbzliiOYB5G03wD7zPFy18UAL//9iPDTz54kD72+RpCPE+xtnuBLVMFFN99+5y8jC6R2vIAA8esDU0SwNe/sLVpX6cEp2NqHgRyOtJTMYqopxOTuMqSdZy X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > --- > arch/arm64/Kconfig | 1 - > arch/arm64/include/asm/percpu.h | 24 ------------------------ > 2 files changed, 25 deletions(-) That is _entirely_ dependent on the system, so this isn't the right approach. I also don't think it's something we particularly want to micro-optimise to accomodate systems that suck at atomics. Will > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 38dba5f7e4d2..5e7e2e65d5a5 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -205,7 +205,6 @@ config ARM64 > select HAVE_EBPF_JIT > select HAVE_C_RECORDMCOUNT > select HAVE_CMPXCHG_DOUBLE > - select HAVE_CMPXCHG_LOCAL > select HAVE_CONTEXT_TRACKING_USER > select HAVE_DEBUG_KMEMLEAK > select HAVE_DMA_CONTIGUOUS > diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h > index b57b2bb00967..70ffe566cb4b 100644 > --- a/arch/arm64/include/asm/percpu.h > +++ b/arch/arm64/include/asm/percpu.h > @@ -232,30 +232,6 @@ PERCPU_RET_OP(add, add, ldadd) > #define this_cpu_xchg_8(pcp, val) \ > _pcp_protect_return(xchg_relaxed, pcp, val) > > -#define this_cpu_cmpxchg_1(pcp, o, n) \ > - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) > -#define this_cpu_cmpxchg_2(pcp, o, n) \ > - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) > -#define this_cpu_cmpxchg_4(pcp, o, n) \ > - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) > -#define this_cpu_cmpxchg_8(pcp, o, n) \ > - _pcp_protect_return(cmpxchg_relaxed, pcp, o, n) > - > -#define this_cpu_cmpxchg64(pcp, o, n) this_cpu_cmpxchg_8(pcp, o, n) > - > -#define this_cpu_cmpxchg128(pcp, o, n) \ > -({ \ > - typedef typeof(pcp) pcp_op_T__; \ > - u128 old__, new__, ret__; \ > - pcp_op_T__ *ptr__; \ > - old__ = o; \ > - new__ = n; \ > - preempt_disable_notrace(); \ > - ptr__ = raw_cpu_ptr(&(pcp)); \ > - ret__ = cmpxchg128_local((void *)ptr__, old__, new__); \ > - preempt_enable_notrace(); \ > - ret__; \ > -}) > > #ifdef __KVM_NVHE_HYPERVISOR__ > extern unsigned long __hyp_per_cpu_offset(unsigned int cpu); > -- > 2.51.0 >