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Message-ID: <1332748920.16159.65.camel@twins>
Subject: Re: CPU Hotplug rework
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Rusty Russell <rusty@rustcorp.com.au>
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Date: Mon, 26 Mar 2012 10:02:00 +0200
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On Mon, 2012-03-26 at 11:11 +1030, Rusty Russell wrote:
> Obviously, having callbacks hanging around until the CPU comes back is
> not viable, nor is blocking preempt during the callbacks.  Calling
> get_online_cpus() is too heavy. 

-rt has patches (albeit somewhat ugly) to make get_online_cpus() a br
style rw-lock. That is, it makes the read side a per-cpu lock/counter so
that its much faster and only touches cpu-local state in the common
case.

It would be good to clean those up and make get_online_cpus() fast and
usable.