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Re: [Xen-devel] [PATCH 7/7] introduce write-once optimization

To: Jan Beulich <JBeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 7/7] introduce write-once optimization
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 22 Sep 2009 09:27:02 +0100
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On 21/09/2009 13:12, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> This one is likely the most questionable part: Realizing that the
> compiler can do a much better job in terms of CSE when the variables
> needed are constant, this introduces and extension to the read-mostly
> variables, allowing variables to be marked as being written just
> during boot initialization.

How much of a win overall was this? The main concern comes from mixing the
two aliased variables within a single linkage unit, where it will be hard to
know how clever the compiler might be with inlining and inter-function
optimisations.

 -- Keir



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