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3. Kernel

3.1. Kernel Platform Enablement

This release introduces support for Intel's new platforms, code-named Boxboro-EX and Boxboro-MC, AMD's new processor family, code-named Magny-Cours and IBM's Power7 processor.

3.2. Kernel Generic Features

The recommended minimal memory requirement on x86 and x86_64 for Red Hat Enterprise Linux 5.5 is now 1GB per logical CPU.


A logical CPU is defined as any entity that can be scheduled (i.e. every core or thread in a multi-core or multi-thread processor is defined as a logical CPU).
Detecting kernel tasks stuck in the uninterruptible sleep state
In some circumstances, tasks in the kernel may permanently enter the uninterruptible sleep state (D-State), making the system impossible to shut down. With this update, the Detect Hung Task kernel thread has been added, providing the ability to detect tasks permanently stuck in the D-State.
This new feature is controlled by the CONFIG_DETECT_HUNG_TASK kernel flag. When set to "y" tasks stuck in the D-State are detected; when set to n it is off. The default value for the CONFIG_DETECT_HUNG_TASK flag is y.
Additionally, the CONFIG_BOOTPARAM_HUNG_TASK_PANIC flag has been added. When set to y, a kernel panic is triggered when a task stuck in the D-State is detected. The default value for the CONFIG_BOOTPARAM_HUNG_TASK_PANIC flag is n.
Signed s390 Kernel Modules
Starting at Red Hat Enterprise Linux 5.5, all s390 kernel modules are now signed. BZ#483665

Note: This documentation is provided {and copyrighted} by Red Hat®, Inc. and is released via the Open Publication License. The copyright holder has added the further requirement that Distribution of substantively modified versions of this document is prohibited without the explicit permission of the copyright holder. The CentOS project redistributes these original works (in their unmodified form) as a reference for CentOS-5 because CentOS-5 is built from publicly available, open source SRPMS. The documentation is unmodified to be compliant with upstream distribution policy. Neither CentOS-5 nor the CentOS Project are in any way affiliated with or sponsored by Red Hat®, Inc.