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Re: [dm-devel] [PATCH 4/5] aio: vmap ringbuffer



On Mon, Oct 08, 2012 at 11:39:19PM -0700, Kent Overstreet wrote:
> It simplifies a lot of stuff if the ringbuffer is contiguously mapped
> into kernel space, and we can delete a lot of code - in particular, this
> is useful for converting read_events() to cmpxchg.

1) I'm concerned that Our Favourite Database Benchmarkers will see an
effect of having more TLB pressure from that mapping.  kmap_atomic()
should be cheaper.  We'll need to measure the difference.

2) I'm not at all convinced that the current ring semantics are safe
with cmpxchg(), more in the next patch.

- z


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