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RE: [Xen-devel] ac_timer: time to say goodbye?

  • To: "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
  • Date: Mon, 23 May 2005 21:12:05 +0100
  • Delivery-date: Mon, 23 May 2005 20:11:27 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcVf0fuq2Yt5GIupSrGQlgxKTX+ysQAAPVlg
  • Thread-topic: [Xen-devel] ac_timer: time to say goodbye?


> It appears that the ac_timer code is not used very much 
> anymore.  (Not that it's not used at all, just not very 
> much... grep for ac_timer.)  It's kind of a heavyweight 
> mechanism for a hypervisor... I wonder if it might be 
> possible to dispense with it entirely?
> The reason I ask now is that, as part of the ia64 CONFIG_VTI 
> checkin, some new timer code got added that makes use of 
> ac_timer and I'm concerned that this might be a step in the 
> wrong direction.
> As domains more completely manage their own timer interrupts, 
> the only use for time in Xen itself is for time-slicing 
> domains, correct?
> Should ac_timer be removed and replaced by a lighter weight 
> mechanism, or at least its use deprecated?

Heavy weight? It's a basic heap (priority queue) implementation. 
Seems to me like a perfectly sensible thing to have in a hypervisor, and
its used extensively by all the schedulers.


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