![]() ![]() Second, the Linux TCP stack has many critical features and very good debugging capabilities. We hope Netmap will occupy this niche, and we are actively supporting it with our patches. ![]() The patch code has been submitted to the project and is available on GitHub. There are two general themes: first, there is no stable open-source partial kernel bypass technology yet. As Bertin writes, most of what CloudFlare needed was the ability to split queues: “the only difference is the nm_open() call, which uses the new syntax netmap:ifname~queue_number.” I red about netmap which allows user programmers to access packets in the user space, that means user applications can read / send network packets very quickly using this netamp. In this way, if a user requests a pair of rings (for example using nmopen(netmap:eth0-4) ) it will actually get a reference to both the number 4 RX and TX rings, while keeping the other rings attached to the kernel stack. The installation is much simpler and we dont really need to apply netmap patches manually. First we modified netmap to leave queues that are not explicitly requested to be in netmap mode attached to the host stack. The combined result is a TCP/IP stack doing packet I/O via netmap. Like all the best hacks, it's small and simple. The netmap driver has updated/improved quite significantly the last time I evaluated it. drv-netif-netmap is a netmap network interface for rump kernels. We call this functionality: "single RX queue mode".” Instead of using Netmap's default functionality, which bumps all received packet queues away from the kernel, “We want to keep most of the RX queues back in the kernel mode, and enable Netmap mode only on selected RX queues. To get what it wanted, Bertin says, the company settled on writing modifications to the Netmap Project. The small number of "valid" packets are injected back to the kernel and handled in the same way as usual traffic.” Most of the packets are dropped, as they belong to a flood. This application filters the packets at very high speed. As Gilberto Bertin writes: “During packet floods we offload selected network flows (belonging to a flood) to a user space application. ![]()
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