From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@eu.citrix.com>
Subject: Re: [PATCH] re-order struct domain fields
Date: Mon, 19 Jan 2015 16:25:13 +0000
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To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>, Keir Fraser <keir@xen.org>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>
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On Mon, 2015-01-19 at 15:42 +0000, Jan Beulich wrote:
> ... to reduce padding holes.
> 
> I also wonder whether having independent spin locks side by side is
> really a good thing cache-line-bouncing-wise.

AIUI the general wisdom is to put each spinlock next to the data it
protects (I suppose on the assumption that after acquiring the lock you
will next touch that data).

Is the problem is that the domain_lock doesn't actually protect anything
in this struct since it is a more umbrella lock, so there is nothing to
put next to it?

You could move either it or the page lock below all the page counts
stuff.

Ian.