Re: [Bloat] high speed networking from userspace
On Mon, 12 Mar 2012 17:09:44 -0700, Dave Taht dave.t...@gmail.com wrote: is the by the same guy that did QFQ, and the results are quite impressive. He (today) announced support for this interface for Linux. shades of VJ's 'network channels'! already implemented: see o http://www.ioremap.net/node/12 o http://www.ioremap.net/taxonomy/term/6 and all netdev discussions several years ago. HGN ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
[Bloat] high speed networking from userspace
Hi, Dave mentioned me the thread about netmap on this list, to which i just subscribed. Some of the posts are referring to Van Jacobson's network channels and to previous experiments or implementations dating back to 2006 e.g. http://www.ioremap.net/taxonomy/term/6 I am glad to see that there were previous attempts at addressing the problem. However before dismissing things as 'done before' i would suggest some performance comparison. For netmap what i can offer at the moment is some data comparing raw packet I/O performance with various sockets families, libpcap, PACKET_TX_RING on linux, and even the in-kernel packet generator in Linux. See for instance see a recent ACM Queue paper (freely accessible), fig.4 and 5 http://queue.acm.org/detail.cfm?id=2103536 In all these cases netmap is one order of magnitude or more faster than the alternatives. Unfortunately I cannot find any actual performance data on netchannel except those from the LCA'06 Van Jacobson slides, where they show about 2x speedup over the host stack. The original netchannel site reports 404 on all links, e.g. http://tservice.net.ru/~s0mbre/blog/2006/10/26#2006_10_26 If someone had some performance data or examples of technologies that work well i would be grateful to see them. Comparing netmap with VJ network channels: - both try to remove skbuf, and move processing out of the interrupt/kernel bottom half and into the user thread (above or below the userland/kernel barrier) to improve cache locality and for other good reasons. These two are key ideas for improving performance, which for instance PF_PACKET does not use (convenient as it does not need driver modifications, but there is a huge cost in performance.) I cannot easily tell whether netchannel implements any of these features: - userspace visible buffers (saves a memory copy and data access which may be helpful for packet forwarding apps where you only look at part of the payload) - poll-able file descriptor (useful to build a pcap layer on top of the packet I/O framework) cheers luigi ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
Re: [Bloat] high speed networking from userspace
On Tue, 13 Mar 2012 13:28:52 +0100 Hagen Paul Pfeifer ha...@jauu.net wrote: On Mon, 12 Mar 2012 17:09:44 -0700, Dave Taht dave.t...@gmail.com wrote: is the by the same guy that did QFQ, and the results are quite impressive. He (today) announced support for this interface for Linux. shades of VJ's 'network channels'! already implemented: see o http://www.ioremap.net/node/12 o http://www.ioremap.net/taxonomy/term/6 and all netdev discussions several years ago. HGN User space networking works well for single application be it routing, bridging, network trading, or single appliance. It doesn't work on a multi-application environment (ie desktop). The gain is only because the userspace code can choose to do less, but do it faster. So if you want full stack, and firewall; don't bother. ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
Re: [Bloat] high speed networking from userspace
On Tue, 13 Mar 2012 09:03:57 -0700, Stephen Hemminger wrote: User space networking works well for single application be it routing, bridging, network trading, or single appliance. It doesn't work on a multi-application environment (ie desktop). The gain is only because the userspace code can choose to do less, but do it faster. So if you want full stack, and firewall; don't bother. Thanks for the additional comments, that's why I wrote see netdev discussions. In sum: if you strip, disable, swap-out functionality you can gain speed/latency - sounds like a universally valid statement ... HGN ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
Re: [Bloat] high speed networking from userspace
On Tue, 2012-03-13 at 20:08 +0100, Luigi Rizzo wrote: The firewall is actually one place where an efficient I/O mechanism is really useful. Netmap (or the netfilter API or netgraph in FreeBSD, if they were not built on top of skbufs/mbufs) give you an ideal place to efficiently drop rogue traffic, and reinject the interesting one in the stack for further processing. Also the concepts used in netmap (and in VJ's netchannel) are not confined to userspace networking. Even in the kernel one can and probably should: - get rid of skbufs/mbufs even in the kernel (replacing them with cheaper containers or data copies) - do more packet coalescing (software RSC is an example), to amortize certain costs over larger batches; - move work away from the interrupt/polling threads and closer to the user thread (for better cache locality and load management) The real gain of these mechanisms, i think, is having the option to avoid costly operations when you don't need them. That's the message i would like to convey. Of course everything would be more convincing if i came up with a full skbuf-less in-kernel stack and not just the bottom layer+libpcap :) OK, but what about process scheduler and ability to queue packets somewhere if your low priority application is stalled because of some high priority stuff coming, or what happens if your tcp receive windows are 16Mbytes per flow... Pre-allocating huge ring buffers is not an option if you handle thousand of flows. We could avoid memory allocators everywhere and come back to 30 years old designs and MSDOS. But thats not the path taken by modern stuff. netchannels have the multiplex/demux problem, and this need some hardware support. Once you have decent hardware support, and xx core machines, you can scale as you need with traditional stacks, as long as you fully understand cache issues and memory locality. Most problems come if you want to use NICs with one queue and one cpu. This just doesnt make sense in 2012, does it ? Sure, all sort of tricks can be used to implement full stack in user land and be fast. Just make sure a NIC can be efficiently shared by this application and others as well. We had the opposite (implement a web server in kernel) and it was probably an interesting idea in its time, but in the long term, you can see nobody uses this anymore. ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
[Bloat] high speed networking from userspace
http://info.iet.unipi.it/~luigi/netmap/ is the by the same guy that did QFQ, and the results are quite impressive. He (today) announced support for this interface for Linux. shades of VJ's 'network channels'! -- Dave Täht SKYPE: davetaht US Tel: 1-239-829-5608 http://www.bufferbloat.net ___ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
