On 07/19/2011 08:23 PM, Jan Kiszka wrote:
On 2011-07-19 19:17, Avi Kivity wrote: > On 07/19/2011 08:14 PM, Jan Kiszka wrote: >> >> Another improvement - unfortunately less transparent for user space - >> would be to overcome the single ring buffer that forces us to hold a >> central lock in user space while processing the entries. We rather need >> per-device rings. While waiting for coalesced VGA MMIO being processed, >> way too many kittens are killed. >> >> I have this on our agenda, but I wouldn't be disappointed as well if >> someone else is faster. > > The socket mmio would have accomplished this as well. I haven't followed the outcome in all details - is that approach dead due to its complexity? > One thing to > beware of is to preserve correctness: > > 1) write to 0xa0000 (queued) > 2) write to 0xa0002 (queued) > 3) remap 0xa0000 region (executed) Obviously, there must be 3a) here: drain all affected queues.
How do you implement this 3a, if your consumers are outside the main process? I guess you could have an additional synchonize API (for in-kernel consumers) or RPC (for external process consumers), but then this is no longer a simple API.
> 4) write to 0xa000 (queued) > 5) drain queue > > writes 1 and 2 go to the wrong place. >
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