* iWarp
OS bypass eliminates overhead
By Kris Meier
The demand for higher-speed server interconnects to support clustering, storage networks and bulk data movement continues to drive Ethernet’s evolution. In transitioning from 1G to 10G bit/sec data rates, Ethernet is poised to handle the most demanding data center applications in these three areas.
However, taking full advantage of this tenfold increase in performance requires the elimination of the three elements of host CPU overhead related to networking: buffer copies, transport processing and application context switches. Recognizing the host CPU overhead problem, the RDMA Consortium and IETF have developed a set of standard extensions to Ethernet and TCP/IP that eliminate all three sources of overhead. Collectively, these specifications are called iWarp.
While Remote Direct Memory Access (RDMA ) and Transport Offload Engines have made great strides in reducing overhead, a full 40% of network overhead is attributed to application context switches. Context switches occur when process execution moves from user space to kernel space. Of the three sources of network overhead, context switches have been discussed the least and warrant further consideration.
Simply put, user space is where all user programs execute. Historically, applications operating in user space make system calls into the kernel for privileged operations such as I/O commands to network or storage devices.
Kernel space is where the operating system, device drivers and hardware interrupt handlers run. The kernel provides a safe interface to hardware, provides interprocess security, gives different processes a fair share of the resources, and arbitrates access to resources/hardware.
For the full story, please go to:
https://www.nwfusion.com/news/tech/2005/013105techupdate.html?nlt
