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Re: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id() [0/2]

To: "Santos, Jose Renato G" <joserenato.santos@xxxxxx>, Keir Fraser <keir@xxxxxxxxxxxxx>, "Apparao, Padmashree K" <padmashree.k.apparao@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id() [0/2]
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 07 Dec 2006 12:01:46 +0000
Cc: "Turner, Yoshio" <yoshio_turner@xxxxxx>, Jose Renato Santos <jsantos@xxxxxxxxxx>, G John Janakiraman <john@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] Reduce overhead in find_domain_by_id() [0/2]
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On 7/12/06 03:49, "Santos, Jose Renato G" <joserenato.santos@xxxxxx> wrote:

> Can't think of anything else. If you want I can remove these and submit
> a revised patch.
> It seems that there is not much more we could remove. Not sure if you
> have something else in mind...

I suppose the patch isn't actually as big as I first imagined. I'll review
it and probably apply it pretty much as is. It's just that RCU has always
seemed rather over complicated to me (lots of different queues, for example)
for what should be a rather simple concept to implement. This is possibly
just ignorance on my part. :-)

As for per-cpu refcounts, I suspect a better scheme would be
find_domain_by_id_noref(). Idea being that often we take a reference for a
short period of time (in particular, scope of one function) and with delayed
destruction we can now safely use a found domain pointer with no refcnt
increment.

 -- Keir


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