Re: [PATCH 00/25] mm: Preemptibility -v7

[Andi Kleen]

> Its nesting hundreds of spinlocks (255+) make the preempt debug code
> unhappy, it also causes fun latencies when you do start KVM/GRU
> Although arguably that's the least convincing reason to do all this its
> the one that got me to actually compose this series -- I really should
> write a new leader..
Least Convincing is a good description...
Tuning operations which only happen once is not very interesting, 
especially if that affects
fast paths.

> Making all this preemptible also allows making the whole mmu_gather
> thing preemptible, which is something we've wanted to do for a long
> while, it also allows XPMEM or whatever that thing was called (Andrea
> knows) and of course, it moves a part of -rt upstream.

I thought the reason for the preempt off inside the mmu gather region was
to stay on the same CPU for local/remote flushes. How would it change that?

> If we decide to keep patch 24, it also simplifies the truncate path
> quite a bit.
That sounds like a good thing. Making truncate simpler is always good.

-Andi
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