From: "Christoph Lameter (Ampere)" <cl@gentwo.org>
To: Dev Jain <dev.jain@arm.com>
Cc: Will Deacon <will@kernel.org>, Jisheng Zhang <jszhang@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
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
Date: Tue, 17 Feb 2026 09:19:22 -0800 (PST) [thread overview]
Message-ID: <6d30176d-9673-287e-4658-a5e9e6e5d649@gentwo.org> (raw)
In-Reply-To: <89606308-3c03-4dcf-a89d-479258b710e4@arm.com>
On Mon, 16 Feb 2026, Dev Jain wrote:
> By coincidence, Yang Shi has been discussing the this_cpu_* overhead
> at [2].
Yang Shi is on vacation but we have a patchset that removes
preempt_enable/disable from this_cpu operations on ARM64.
The performance of cmpxchg varies by platform in use and with the kernel
config. The measurements that I did 2 years ago indicated that the cmpxchg
use with Ampere processors did not cause a regression.
Note that distro kernels often do not enable PREEMPT_FULL and therefore
preempt_disable/enable overhead is not incurred in production systems.
PREEMPT_VOLUNTARY does not use preemption for this_cpu ops.
next prev parent reply other threads:[~2026-02-17 17:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-15 3:39 Jisheng Zhang
2026-02-16 10:59 ` Dev Jain
2026-02-16 11:00 ` Will Deacon
2026-02-16 15:29 ` Dev Jain
2026-02-17 13:53 ` Catalin Marinas
2026-02-17 15:00 ` Will Deacon
2026-02-17 16:48 ` Catalin Marinas
2026-02-18 4:01 ` K Prateek Nayak
2026-02-18 9:29 ` Catalin Marinas
2026-02-17 17:19 ` Christoph Lameter (Ampere) [this message]
2026-02-20 6:14 ` Jisheng Zhang
2026-02-18 22:07 ` Shakeel Butt
2026-02-20 6:20 ` Jisheng Zhang
2026-02-20 23:27 ` Shakeel Butt
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