Messages in this thread | | | Date | Thu, 02 Apr 2009 14:48:11 +0300 | From | Avi Kivity <> | Subject | Re: [RFC PATCH 00/17] virtual-bus |
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Gregory Haskins wrote:
>> There is no choice. Exiting from the guest to the kernel to userspace >> is prohibitively expensive, you can't do that on every packet. >> >> > > Now you are making my point ;) This is part of the cost of your > signaling path, and it directly adds to your latency time.
It adds a microsecond. The kvm overhead of putting things in userspace is low enough, I don't know why people keep mentioning it. The problem is the kernel/user networking interfaces.
> You can't > buffer packets here if the guest is only going to send one and wait for > a response and expect that to perform well. And this is precisely what > drove me to look at avoiding going back to userspace in the first place. >
We're not buffering any packets. What we lack is a way to tell the guest that we're done processing all packets in the ring (IOW, re-enable notifications).
-- error compiling committee.c: too many arguments to function
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