Ingo Molnar wrote:
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> nice stuff!
>
> I suspect the extra cost might be worth it for two reasons: 1) we could 
> optimize the cross-call implementation further

Unfortunately, I think the kmalloc fix for the RCU issue is going to
hurt quite a lot.

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>  2) on systems where TLB 
> flushes actually matter, the ability to overlap multiple TLB flushes to 
> the same single CPU might improve workloads.
>   

...perhaps.

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> FYI, i've created a new -tip topic for your patches, tip/x86/tlbflush. 
> It's based on tip/irq/sparseirq (there are a good deal of dependencies 
> with that topic).
>   

Really?  I didn't see much conflict when rebasing onto current tip.git. 
Just an incidental context conflict in entry_arch.h.

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> It would be nice to see some numbers on sufficiently SMP systems, using 
> some mmap/munmap intense workload.

I've attached my test program: tlb-mash.c.  Compile with "gcc -o
tlb-mash tlb-mash.c -lpthread" and run with ./tlb-mash X, where X is the
number of threads to run (2x cpus works well).  It keeps running until
killed, with each thread repeatedly mprotecting a page within a shared
mapping.

    J