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

[Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>]

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.

Agreed.


Juergen

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Juergen Gross                             Principal Developer
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