Re: [Question]About KVM network zero-copy feature!

(adding Xin Xiaohui to the conversation for comment)

According to the NetworkingTodo page on the KVM wiki, zero-copy RX for 
macvtap is in fact on the roadmap, assigned to Xin:

http://www.linux-kvm.org/page/NetworkingTodo

The Release Notes for RHEL 6.2 (originally published on 12/06/2011) also 
specifically mention macvtap/vhost zero-copy capabilities as being 
included as a Technology Preview:

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/6.2_Release_Notes/virtualization.html

Since I've been unable to find much information on the current status of 
this development, can anyone confirm if this functionality is still in 
the works? If so, is there any planned ETA?

Thanks,
Robert Vineyard


On 08/11/2012 05:54 PM, Robert Vineyard wrote:

quoted

On Fri, 10 Aug 2012 11:34:32 +0800
"Peter Huang(Peng)" [off-list ref] wrote:

quoted

I searched from git-log, and found that until now we have vhost TX
zero-copy experiment feature, how
about RX zero-copy?

On 08/11/2012 04:55 PM, Stephen Hemminger wrote:

quoted

There is no guarantee that packet will ever be read by receiver. This
means zero-copy could
create memory back pressure stalls.

It would be handy if this could be an optional feature, perhaps not
enabled by default due to the problem with stalls you mentioned. I would
love to see RX zero-copy implemented natively in KVM, as it might
alleviate the need for custom solutions like vPF_RING:

http://www.ntop.org/products/pf_ring/vpf_ring/

Every time a packet is copied, especially from kernel space to user
space, there is an opportunity for it to be dropped on its way to the
receiving application - which is unacceptable when monitoring high-speed
networks for security or bandwidth accounting purposes.

I am attempting to find a highly-efficient way to deploy virtualized
network monitoring sensors (Snort, for example). Ideally I want to
exploit symmetric hardware-based RSS and SR-IOV functionality for
load-balancing and packet distribution completely in ASIC. I've found
other existing work in this area (also using custom drivers) indicating
significant performance gains in the non-virtualized case:

http://www.ndsl.kaist.edu/~shinae/papers/TR-symRSS.pdf

Is there any interest in exploring native RX zero-copy within the
mainline KVM networking code?

Thanks,
Robert Vineyard
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html