Kernel Updates; General Kernel Feature Support - Red Hat ENTERPRISE LINUX 5.4 - RELEASE NOTES Release Note

of the device. The updated qeth driver now correctly reads the new version string format of
HiperSockets, allowing for a standardization of output format.
• In Red Hat Enterprise Linux 5.4, the s390utils package has been rebased to version 1.8.1. For
a full list of features that this rebase provides, please refer to the Package Updates section of the
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Technical Notes (BZ#477189)
.
• In the kernel, a sysfs interface has been implemented to associate actions to shutdown triggers.
For more details on this feature, refer to the "Shutdown actions" chapter in IBM's "Device Drivers,
Features, and Commands" book located at:
development_documentation.html

8. Kernel Updates

8.1. General Kernel Feature Support

• Asymmetric Logical Unit Access (ALUA) support in device-mapper-multipath has been updated,
adding explicit ALUA support for Clariion storage. Earlier versions of Red Hat Enterprise Linux 5
added support for implicit ALUA (i.e. the operating system is not aware of which storage device
paths have optimized performance and which have non-optimized performance). If the operating
system consistently sends I/O on a non-optimized path, then the storage device may transparently
make that path optimized, improving performance and causing idle paths to become non-optimized.
Red Hat Enterprise Linux 5.4 introduces explicit ALUA support for Clariion storage (i.e. the operating
system exchanges information with the storage device and is able to select the paths that have
optimized performance).
• Previously, support for raw devices in the upstream kernel was deprecated. However, this support
has been returned to the kernel. Consequently, in Red Hat Enterprise Linux 5.4, support for raw
devices has also been returned. Additionally, the initscripts packages have been updated, adding
the previously dropped functionality of raw
• KVM guest-smp tlb flushing without mmu-notifiers could corrupt memory as a KVM may add
pages to the kernel freelist while another vcpu may still be writing to them through guest mode. This
update adds mmu-notifier support to the kernel and also corrects a bug found in an earlier patch
wherein mm_struct was grown by existing drivers and caused a failed kABI check. This bug has
been corrected by using an index that resides in an unused padding hole to avoid expanding the
size.(Bugzilla #485718
structure
• Pointer and signed arithmetic overflow wrapping has not previously been defined in the Linux kernel.
This could cause GCC (GNU C Compiler) to assume that wrapping does not occur and attempt
to optimize the arithmetic that the kernel may require for overflow testing. This update adds the -
fwrapv variable to GCC CFLAGS in order to define wrapping
• An issue of contention between processes vying for the same memory space in high end
systems was recently identified by TPC-C (Transaction Processing Council) benchmarking. This
update includes fast-gup patches which use direct IO and provide a significant (up to 9-10%)
performance improvement. This update has been tested thoroughly and is used in the 5.4 kernel to
improve scalability. For further information, see this
• A new tunable parameter has been added to this kernel, allowing system administrators to change
the maximum number of modified pages kupdate writes to disk per iteration each time it runs.
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http://www.ibm.com/developerworks/linux/linux390/
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(BZ#482737)
devices.(BZ#472891)
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)
(BZ#479881)
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behavior.(Bugzilla #491266
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article (Bugzilla #474913
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Kernel Updates
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