linux-kernel - Re: [PATCH 3/3] LoongArch: Allow to enable PREEMPT

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Message-ID: <ZzYMie7ktV8ByaQF@demetrius>
Date: Thu, 14 Nov 2024 08:43:21 -0600
From: Clark Williams <clrkwllms@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Huacai Chen <chenhuacai@...nel.org>,
	Huacai Chen <chenhuacai@...ngson.cn>,
	Xuerui Wang <kernel@...0n.name>, loongarch@...ts.linux.dev,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-rt-devel@...ts.linux.dev, Guo Ren <guoren@...nel.org>,
	Jiaxun Yang <jiaxun.yang@...goat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] LoongArch: Allow to enable PREEMPT_RT

On Thu, Nov 14, 2024 at 02:29:56PM +0100, Sebastian Andrzej Siewior wrote:
> 
> Ach okay. So the pure read on the slow bus causes a delay because the
> CPU is stalled. That is not limited to chrony but should also have an
> affect if the user uses hwclock to read/ write the time.
> 
> Sebastian
> 

We see similar problems with chronyd accessing the RTC on aarch64
systems that use UEFI. Accessing anything via the EFI Runtime is very
slow. Probably going to turn off 'rtcsync' in chronyd when running
low-latency workloads. 

Clark

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