Chris Wright wrote:
There's been a number of different discussions re: getting copyless virtio
net (esp. for KVM). This is just a poke in that general direction to
stir the discussion. I'm interested to hear current thoughts
I believe that copyless networking is absolutely essential.
For transmit, copyless is needed to properly support sendfile() type
workloads - http/ftp/nfs serving. These are usually high-bandwidth,
cache-cold workloads where a copy is most expensive.
For receive, the guest will almost always do an additional copy, but it
will most likely do the copy from another cpu. Xen netchannel2
mitigates this somewhat by having the guest request the hypervisor to
perform the copy when the rx interrupt is processed, but this may still
be too early (the packet may be destined to a process that is on another
vcpu), and the extra hypercall is expensive.
In my opinion, it would be ideal to linux-aio enable taps and packet
sockets. io_submit() allows submitting multiple buffers in one syscall
and supports scatter/gather. io_getevents() supports dequeuing multiple
packet completions in one syscall.
--
error compiling committee.c: too many arguments to function
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