Re: [patch 28/34] Xen-pv_ops: Xen SMP guest support

[Zachary Amsden]

Benjamin LaHaise wrote:
>   
> > +/*
> > + * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
> > + * *much* faster this way.
> > + */
> >     
>
> Are you switching mms in order to avoid all of the overhead associated with 
> flushing an active mm during task exit?  If so, it makes much more sense to 
> do this in the generic helper, as it should be a win on x86 and x86-64 
> where switching to init_mm is relatively low cost given the support for 
> global pages.  I'll run some tests on a couple of systems this evening and 
> post the results.
>   

I tried this experiment on both x86 and x86-64 and I recall not seeing 
any effect.  The mmu_gather optimization does most of this already.

Zach
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