Netmap - a framework for fast packet I/O
VALE - a Virtual Local Ethernet using the netmap API========================================================================
NETMAP is a framework for very fast packet I/O from userspace. VALE is an equally fast in-kernel software switch using the netmap API. Both are implemented as a single kernel module for FreeBSD and Linux, and can deal with line rate on real or emulated 10 Gbit ports. See details at
http://info.iet.unipi.it/~luigi/netmap/In this directory you can find source code (BSD-Copyright) for FreeBSD and Linux. Note that recent FreeBSD distributions already include both NETMAP and VALE.
For more details please look at the manpage (netmap.4) and netmap home page above.
Netmap is mostly useful for userspace applications that must deal with raw packets: traffic generators, sinks, monitors, loggers, software switches and routers, generic middleboxes, interconnection of virtual machines.
In this distribution you will find some example userspace code to build a generator, a sink, and a simple bridge. The kernel module implements a learning ethernet bridge. We also include patches for some applications (noticeably libpcap) so you can run any libpcap client on top of netmap hopefully at a higher speed.
Netmap alone DOES NOT accelerate your TCP. For that you need to implement your own tcp/ip stack probably using some of the techniques indicated below to reduce the processing costs.
netmap uses a number of techniques to establish a fast and efficient path between applications and the network. In order of importance:
1. I/O batching
2. efficient device drivers
3. pre-allocated tx/rx buffers
4. memory mapped buffersDespite the name, memory mapping is NOT the key feature for netmap's speed; systems that do not apply all these techniques do not achieve the same speed and efficiency.
Netmap clients use a select()-able file descriptor to synchronize with the network card/software switch, and exchange multiple packets per system call through device-independent memory mapped buffers and descriptors. Device drivers are completely in the kernel, and the system does not rely on IOMMU or other special mechanisms.
A kernel module (netmap.ko or netmap_lin.ko) implements the core NETMAP routines and the VALE switch. Netmap-aware device drivers are needed to use netmap on ethernet ports. To date, we have support for Intel ixgbe (10G), e1000/e1000e/igb (1G), Realtek 8169 (1G) and Nvidia (1G).
If you do not have a supported device, you can still try out netmap (with reduced performance) because the main kernel module emulates the netmap API on top of standard device drivers.
Since recent FreeBSD distributions already include netmap, you only need build the new kernel or modules as below:
add 'device netmap' to your kernel config file and rebuild a kernel. This will include the netmap module and netmap support in the device drivers. Alternatively, you can build standalone modules (netmap, ixgbe, em, lem, re, igb)
sample applications are in the examples/ directory in this archive, or in src/tools/tools/netmap/ in FreeBSD distributions
On Linux, netmap is an out-of-tree module, so you need to compile it from these sources. The Makefile in the LINUX/ directory will also let you patch device driver sources and build some netmap-enabled device drivers.
make sure you have kernel sources matching your installed kernel (headers only suffice, if you want NETMAP/VALE but no drivers)
build kernel modules and sample applications: If kernel sources are in /foo//linux-A.B.C/ , then you should do
cd netmap/LINUX
make NODRIVERS=1 KSRC=/foo/linux-A.B.C/ # only netmap make KSRC=/a/b/c/linux-A.B.C/ # netmap+device drivers
make KSRC=/a/b/c/linux-A.B.C/ apps # builds sample applications
You can omit KSRC if your kernel sources are in a standard place.
if you use distribution packages, source may not contain headers (e.g., on debian systems). Use
make SRC=/a/b/c/linux-sources-A.B/ KSRC=/a/b/c/linux-headers-A.B/The directory examples/ contains some programs that use the netmap API
pkt-gen.c a packet generator/receiver working at line rate at 10Gbit/s
vale-cfg.c utility to configure ports of a VALE switch
bridge.c a utility that bridges two interfaces or one interface
with the host stackFor libpcap and other applications look at the extra/ directory.
pkt-gen is a generic test program which can act as a sender or receiver. It has a large number of options, but the simplest form is:
pkt-gen -i ix0 -f rx # receive and print stats
pkt-gen -i ix0 -f tx -l 60 # send a stream of 60-byte packets(replace ix0 with the name of the interface or VALE port). This should be able to work at line rate (up to 14.88 Mpps on 10 Gbit/interfaces, even higher on VALE) but note the following
Netmap is able to send packets at very high rates, and for simple packet transmission and reception, speed generally not limited by the CPU but by other factors (link speed, bus or NIC hw limitations).
For a physical link, the maximum numer of packets per second can be computed with the formula:
pps = line_rate / (672 + 8 * pkt_size)where "line_rate" is the nominal link rate (e.g 10 Gbit/s) and pkt_size is the actual packet size including MAC headers and CRC. The following table summarizes some results
LINE RATE
pkt_size \ 100M 1G 10G 40G
64 .1488 1.488 14.88 59.52
128 .0589 0.589 5.89 23.58
256 .0367 0.367 3.67 14.70
512 .0209 0.209 2.09 8.38
1024 .0113 0.113 1.13 4.51
1518 .0078 0.078 0.78 3.12On VALE ports, there is no physical link and the throughput is limited by CPU or memory depending on the packet size.
Before reporting slow send or receive speed on a physical interface, check ALL of the following:
CANNOT SET THE DEVICE IN NETMAP MODE:
SENDER DOES NOT TRANSMIT
some switches/interfaces take a long time to (re)negotiate the link after starting pkt-gen; in case, use the -w N option to increase the initial delay to N seconds;
This may cause inability to transmit, or lost packets forthe first few seconds of transmission
RECEIVER DOES NOT RECEIVE
LOWER SPEED THAN LINE RATE
check that your CPUs are running at the maximum clock rate and are not throttled down by the governor/powerd.
make sure that the sender/receiver interfaces and switch have flow control (FC) disabled (either via sysctl or ethtool).
If FC is enabled and the receiving end is unable to copewith the traffic, the driver will try to slow down transmission, sometimes to very low rates.
a lot of hardware is not able to sustain line rate. For instance, ixgbe has problems with receiving frames that are not multiple of 64 bytes (with/without CRC depending on the driver); also on transmissions, ixgbe tops at about 12.5 Mpps unless the driver prefetches tx descriptors. igb does line rate in all configurations. e1000/e1000e vary between 1.15 and 1.32 Mpps. re/r8169 is extremely slow in sending (max 4-500 Kpps)
NETMAP and VALE are projects of the Universita` di Pisa, partially supported by various entities including: Intel Research Berkeley, EU FP7 projects CHANGE and OPENLAB, Netapp/Silicon Valley Community Foundation, ICSI
Author: Luigi Rizzo Contributors: Giuseppe Lettieri Michio Honda Marta Carbone Gaetano Catalli Matteo Landi Vincenzo Maffione
There are a few academic papers describing netmap, VALE and applications. You can find the papers at http://info.iet.unipi.it/~luigi/research.html
Luigi Rizzo, netmap: a novel framework for fast packet I/O, Usenix ATC'12, Boston, June 2012
Luigi Rizzo, Revisiting network I/O APIs: the netmap framework, Communications of the ACM 55 (3), 45-51, March 2012
Luigi Rizzo, Marta Carbone, Gaetano Catalli, Transparent acceleration of software packet forwarding using netmap, IEEE Infocom 2012, Orlando, March 2012
Luigi Rizzo, Giuseppe Lettieri, VALE: a switched ethernet for virtual machines, ACM Conext 2012, Nice, Dec. 2012
Luigi Rizzo, Giuseppe Lettieri, Vincenzo Maffione, Speeding up packet I/O in virtual machines, IEEE/ACM ANCS 2013, San Jose, Oct. 2013