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Date: Mon, 04 May 2009 12:58:38 +0300 From: Avi Kivity <avi@...hat.com> To: Andi Kleen <andi@...stfloor.org> CC: Elad Lahav <elahav@...terloo.ca>, linux-kernel@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH] Implementation of the sendgroup() system call Andi Kleen wrote: >>> My guess it's more the copies than the calls? It sounds like >>> you want sendfile() for UDP. I think that would be a cleaner solution >>> than such a specific hack for your application. It would >>> have the advantage of saving the first copy too and be >>> truly zero copy on capable NICs. >>> >>> >> An aio udp send could accomplish both multiple packets per call, and >> > > AIO sockets are a lot of work. There have been various attempts > over the years, but they are very difficult. This was mostly > for TCP -- possibly UDP would be a bit easier -- but still > many complications. It would also need a lot of changes and > you would need to convince the network maintainers that they > are a good idea. > I would love them for kvm. As far as I understand, the only complication is proper socket destructors so we can put_page() the memory. Right now sendfile() is only usable for read-only files. It's not usable for files that change, or non-file memory. > >>> Or perhaps simple send to a local multicast group and let >>> some netfilter module turn that into regular UDP. >>> >>> >> Sounds hacky and rooty. >> > > rooty? Everyone can send to all directions anyways. > > It wouldn't be perfect, but quite usable as a short term solution > for a production server. > I meant, you need root to insert that netfiler module. It's workable as a one off but it's not something reusable. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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