linux-kernel - Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu

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Message-ID: <alpine.DEB.2.00.1109200957500.8056@router.home>
Date:	Tue, 20 Sep 2011 09:58:41 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Valdis.Kletnieks@...edu, Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for
 this_cpu_read/write()

On Tue, 20 Sep 2011, Thomas Gleixner wrote:

> > What's the latency hit on those very few locations if we simply put our
> > collective foot down and not support a preemptable version of this_cpu_*()?
> > "Yes, you *could* preempt here, but for our collective sanity that's not
> > supported"...
>
> Full ack.

Latency hit could be very significant in various critical kernel paths.
Especially network subsystem, vm event counters etc.

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