linux-kernel - Re: regarding the x86_64 zero-based percpu patches

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Date:	Thu, 15 Jan 2009 14:27:33 -0600 (CST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	travis@....com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>, steiner@....com,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: regarding the x86_64 zero-based percpu patches

On Thu, 15 Jan 2009, Rusty Russell wrote:

> I don't think moving per-cpu areas is going to fly.  We do put complex
> datastructures in there. And you're going to need preempt_disable() on
> all per-cpu ops on many archs to make it work (assuming you use
> stop_machine to do the realloc.  Even a rough audit quickly becomes
> overwhelming: 20 of the first 1/4 of DECLARE_PER_CPUs are non-movable
> datastructures.

Ok then lets go for dynamically growing per cpu areas using 2M virtual
mappings.... At least on 64 bit that should be fine.
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