Messages in this thread | | | Subject | Re: [tip:perfcounters/core] x86: Add NMI types for kmap_atomic | From | Peter Zijlstra <> | Date | Wed, 17 Jun 2009 09:58:38 +0200 |
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On Tue, 2009-06-16 at 13:38 +0100, Hugh Dickins wrote: > > Something else to throw in: what if they were not just atomic, > but also replaced the current sleeping kmaps? i.e. a task context > carries around its own stack of these.
I actually did that once, but it means the task needs to be cpu-affine, because fixmaps have different addresses between cpus. And disabling migration for tasks has subtle side-effects so I dropped that again.
However, I recently considered the possiblity of putting the fixmaps in the new per-cpu address space so that we might use the %gs segment to normalize the fixmap addresses between the cpus.
This would allow full preemptible kmaps (yay for -rt).
However I suspect it might greatly complicate kmaps for the !i386 world.
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