linux-kernel - Re: [PATCH] percpu-refcount: Use normal instead of RCU-sched"

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Message-ID: <20191107162842.2qgd3db2cjmmsxeh@linutronix.de>
Date:   Thu, 7 Nov 2019 17:28:42 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH] percpu-refcount: Use normal instead of RCU-sched"

On 2019-11-07 11:17:49 [-0500], Dennis Zhou wrote:
> Hello,

Hi,

> I just want to clarify a little bit. Is this patch aimed at fixing an
> issue with RT kernels specifically? 

Due to the implications of preempt_disable() on RT kernels it fixes
problems with RT kernels.

> It'd also be nice to have the
> numbers as well as if the kernel was RT or non-RT.

The benchmark was done on a CONFIG_PREEMPT kernel. As said in the commit
log, the numbers were mostly the same, I can re-run the test and post
numbers if you want them.
This patch makes no difference on PREEMPT_NONE or PREEMPT_VOLUNTARY
kernels.

> Thanks,
> Dennis

Sebastian