Messages in this thread | | | Subject | Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() | From | Peter Zijlstra <> | Date | Tue, 05 Jan 2010 09:18:16 +0100 |
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On Mon, 2010-01-04 at 21:10 -0800, Linus Torvalds wrote: > Sounds doable. But it also sounds way more expensive than the current VM > fault handling, which is pretty close to optimal for single-threaded > cases.. That RCU lookup might be cheap, but just the refcount is generally > going to be as expensive as a lock.
Right, that refcount adds two atomic ops, the only grace it has is that its in the vma as opposed to the mm, but there are plenty workloads that concentrate on a single vma, in which case you get an equally contended cacheline as with the mmap_sem.
I was trying to avoid having to have that refcount, but then sorta forgot about the actual fault handlers also poking at the vma :/
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