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Re: [Xen-devel] [PATCH 1/2, v2] x86: replace nr_irqs sized per-domain ar

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 1/2, v2] x86: replace nr_irqs sized per-domain arrays with radix trees
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Wed, 04 May 2011 20:55:02 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Allen M Kay <allen.m.kay@xxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH 1/2, v2] x86: replace nr_irqs sized per-domain arrays with radix trees
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On 04/05/2011 17:13, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> After some offlist discussion, for kztmem (later renamed "the new
> zcache"), I ended up extracting the essence of the radix-tree data
> structure and adapting it inline specifically for my in-kernel tmem
> needs.  While I'm not a fan of duplicating code, this was an
> expedient way to avoid a political quagmire.
> Ideally, the Xen radix-tree.c would support both needs through some
> kind of layering, but if your preference is to go to the upstream
> Linux radix-tree.c, I can probably leverage my inlined-radix-tree
> code into Xen tmem.c.  I don't expect it will be trivial though.

I'm sure I can pull in upstream radix-tree.c and get Xen's tmem ported onto
it. As for performance, I may leave the tagging stuff out as we won't need
it. Then it's just quibbling over RCU overheads, which I would bet are
manageable. We can modify radix-tree.c further if there is good reason for

 -- Keir

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