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Re: [Xen-devel] [Patch 1 of 2]: PV-domain SMP performance XEN-part

  • To: George Dunlap <dunlapg@xxxxxxxxx>
  • From: Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>
  • Date: Mon, 22 Dec 2008 07:10:08 +0100
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Sun, 21 Dec 2008 22:11:05 -0800
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George Dunlap wrote:
> The idea might be interesting, but this implementation needs some
> work.  Xen shouldn't be reading a guest-writable bit of memory to
> determine if it's already delayed the guest; it needs to store that
> information somewhere else.  As it is, a rogue guest could extend its
> time indefinitely by just writing 0 there every couple hundred
> instructions.

Thanks for finding this one!
The correction is quite simple, I can just use sd->delay_desched for
this purpose instead.

> It should probably be something taken care of in the individual
> schedulers, rather than in the abstract scheduling code.
> At any rate, let's see if there's a significant performance difference
> between this and yield-after-spinning-awhile, and then we can work on
> the architecture.



Juergen Gross                             Principal Developer
IP SW OS6                      Telephone: +49 (0) 89 636 47950
Fujitsu Siemens Computers         e-mail: juergen.gross@xxxxxxxxxxxxxxxxxxx
Otto-Hahn-Ring 6                Internet: www.fujitsu-siemens.com
D-81739 Muenchen         Company details: www.fujitsu-siemens.com/imprint.html

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