Oracle Enterprise Linux 6.5 is out!


There was two weeks since RedHat released it’s Enterprise Linux 6.4 (RHEL 6.5 Release Notes). Oracle have followed with Oracle Enterprise Linux 6.5 (Announcement). Some interessting new features comes with this release (OEL6.5/UEK3 Release Notes):

Linux Containers

This Features is fully supported by OEL now.

For the Oracle Database Users:

“Oracle Database is not yet supported for use with Linux Containers. The following information is intended for those who want to experiment with such a configuration.”

The following /proc parameter files may only be set on the host and not for individual containers

  • /proc/sys/fs/aio-max-nr
  • /proc/sys/net/core/rmem_default
  • /proc/sys/net/core/rmem_max
  • /proc/sys/net/core/wmem_default
  • /proc/sys/net/core/wmem_max
  • /proc/sys/net/ipv4/ip_local_port_range

Setting the parameters in the host to the Oracle recommended values sets them for all containers and allows the Oracle database to run in a container. For more information, see Configuring Kernel Parameters. (Bug ID 17217854)

Transparent Huge Pages

This release removes the Transparent Huge Pages (THP) feature. Following extensive benchmarking and testing, Oracle found that THP caused a performance degradation of between 5 and 10% for some workloads. This performance degradation was a result of a slower memory allocator code path being used even when the applications were not using THP. When the fact that huge pages are not swappable was taken into account, the positive effect that THP should provide was outweighed by its negative effects.

After installing this UEK release, you cannot enable THP (for example, by specifying kernel boot parameters). The THP settings under /sys/kernel/mm/transparent_hugepage have also been removed. A future update might contain an updated THP implementation which resolves the performance issue.

Note:This change does not affect support for applications that use explicit huge pages (for example, Oracle Database). (Bug ID 16823432)

One-gigabyte (1 GB) huge pages are not currently supported for the following configurations:

  • HVM guests
  • PV guests
  • Oracle Database

Two-megabyte (2 MB) huge pages have been tested and work with these configurations. (Bug ID 17299364, 17299871, 17271305)

Other features

There are some more interessting features. Please refer to UEK3 Overview