2. Kernel

The kernel shipped in Red Hat Enterprise Linux 6.1 includes several hundred bug fixes for and enhancements to the Linux kernel. For details concerning every bug fixed in and every enhancement added to the kernel for this release, refer to the kernel chapter in the Red Hat Enterprise Linux 6.1 Technical Notes.
Control Groups

Control groups are a feature of the Linux kernel introduced in Red Hat Enterprise Linux 6. Each control group is a set of tasks on a system that have been grouped together to better manage their interaction with system hardware. Control groups can be tracked to monitor the system resources that they use. Additionally, system administrators can use control group infrastructure to allow or to deny specific control groups access to system resources such as memory, CPUs (or groups of CPUs), networking, I/O, or the scheduler.

Red Hat Enterprise Linux 6.1 introduces many improvements and updates to control groups, including the ability to throttle block device Input/Output (I/O) to a particular device, either by bytes per second or I/O Per Second (IOPS).
Additionally, integration with libvirt and other userspace tools is provided by the new ability to create hierarchical block device control groups. The new block device control group tunable group_idle, provides better throughput with control groups while maintaining fairness.
Red Hat Enterprise Linux 6.1 also introduces the new autogroup feature, reducing latencies and allowing for more interactive tasks during CPU intensive workloads. This cgsnapshot tool, providing the ability to take a snapshot of the current control group configuration.


Control Groups and other resource management features are discussed in detail in the Red Hat Enterprise Linux 6 Resource Management Guide
Networking updates

Red Hat Enterprise Linux 6.1 introduces support for Receive Packet Steering (RPS) and Receive Flow Steering (RFS). Receive Packet Steering allows incoming network packets to be processed in parallel over multiple CPU cores. Receive Flow Steering chooses the optimal CPU to process network data intended for a specific application.


kdump is an advanced crash dumping mechanism. When enabled, the system is booted from the context of another kernel. This second kernel reserves a small amount of memory, and its only purpose is to capture the core dump image in case the system crashes.

Red Hat Enterprise Linux 6.1 introduces the kernel message dumper, which is called when a kernel panic occurs. The kernel message dumper provides easier crash analysis and allows 3rd party kernel message logging to alternative targets.
Performance updates and improvements

The kernel in Red Hat Enterprise Linux 6.1 provides the following notable performance improvements:

  • Updates and improvements to Transparent Huge Pages (THP) support
  • Updates to perf_event, adding the new perf lock feature to better analyze lock events.
  • kprobes jump optimization, reducing overhead and enhancing SystemTap performance.
  • Updates to i7300_edac and i7core_edac, providing support for monitoring of memory errors on motherboards using Intel 7300 chipset