linux-kernel - Re: [PATCH 7/9] rcu: use this_cpu_ptr per-cpu helper instead of per_cpu_ptr(p, raw_smp_processor

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Message-ID: <0000013abc638281-aaf452ca-0b94-4d56-8b8d-6b2b0c683668-000000@email.amazonses.com>
Date:	Thu, 1 Nov 2012 14:32:49 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Shan Wei <shanwei88@...il.com>
cc:	paulmck@...ux.vnet.ibm.com, dipankar@...ibm.com,
	Kernel-Maillist <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/9] rcu:  use this_cpu_ptr per-cpu helper instead of
 per_cpu_ptr(p, raw_smp_processor_id())

On Thu, 1 Nov 2012, Shan Wei wrote:

> Paul E. McKenney said, at 2012/11/1 4:08:
> >
> > One thing to keep in mind -- the only purpose of this is to diffuse
> > memory contention.  So there is no need to disable preemption.
>
> same question to me.
> Christoph, maybe __this_cpu_read is a better choice which don't disable preemption.

Correct. Use __this_cpu_read to reduce overhead on processor that require
emulation.

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