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


> -----Original Message-----
> From: Keir Fraser [mailto:keir@xxxxxxxxxxxxx] 
> Sent: Thursday, December 07, 2006 4:02 AM
> To: Santos, Jose Renato G; Keir Fraser; Apparao, Padmashree 
> K; xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: Turner, Yoshio; Jose Renato Santos; G John Janakiraman
> Subject: Re: [Xen-devel] [PATCH] Reduce overhead in 
> find_domain_by_id() [0/2]
> 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. :-)

Yes, the multiple queues seems somewhat complicated, but
I think we need them to be able to handle multiple callbacks.
Maybe we can get rid of of of them ("done")...

> 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.

Good point. This is indeed a much better scheme. I will 
work out a patch for find_domain_by_id_noref().



>  -- Keir

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