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Release Notes for Unbreakable Enterprise Kernel Release 3 Quarterly Update 1

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February 2014


This document contains information on Quarterly Update 1 to the Unbreakable Enterprise Kernel Release 3. This document may be updated after it is released. To check for updates to this document, and to view other Oracle documentation, refer to the Documentation section on the Oracle Technology Network (OTN) Web site:

This document is intended for users and administrators of Oracle Linux. It describes potential issues and the corresponding workarounds you may encounter while using the Unbreakable Enterprise Kernel Release 3 with Oracle Linux 6. Oracle recommends that you read this document before installing or upgrading the Unbreakable Enterprise Kernel Release 3.

Document generated on: 2014-02-14 (revision: 1671)

Table of Contents

1 New Features and Changes
1.1 Notable Changes
1.2 Xen Improvements
1.3 Driver Updates
1.3.1 Storage Adapter Drivers
1.3.2 Network Adapter Drivers
1.3.3 Miscellaneous Drivers
1.4 Technology Preview
1.5 Compatibility
2 Fixed and Known Issues
2.1 Fixed Issues
2.2 Known Issues
3 Installation and Availability
3.1 Switching a System to UEK R3 (ULN)
3.2 Switching a System to UEK R3 (Public Yum)
3.3 Upgrading OFED Packages


The Oracle Linux Unbreakable Enterprise Kernel Release Notes provides a summary of the new features, changes, and fixed and known issues in the Unbreakable Enterprise Kernel Release 3.


This document is written for system administrators who want to use the Unbreakable Enterprise Kernel with Oracle Linux. It is assumed that readers have a general understanding of the Linux operating system.

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Chapter 1 New Features and Changes

The Unbreakable Enterprise Kernel Release 3 (UEK R3) is Oracle's third major release of its heavily tested and optimized operating system kernel for Oracle Linux 6 on the x86-64 architecture. It is based on the mainline Linux kernel version 3.8.13.

The 3.8.13-26 release is the first quarterly update release for UEK R3. It includes security and bug fixes, as well as driver updates.

Oracle actively monitors upstream checkins and applies critical bug and security fixes to UEK R3.

UEK R3 uses the same versioning model as the mainline Linux kernel version. It is possible that some applications might not understand the 3.x versioning scheme. If an application does require a 2.6 context, you can use the uname26 wrapper command to start it. However, regular Linux applications are usually neither aware of nor affected by Linux kernel version numbers.

1.1 Notable Changes


  • To simplify Kdump configuration, support has been added for the crashkernel=auto kernel parameter. For Xen, this parameter is supported only for Domain 0.


    If this parameter is enabled, the output of the dmesg command shows crashkernel=XM@0M. This is normal.


  • The SDT (Statically Defined Tracing) provider has been improved so that probes for kernel modules can now be enabled. Previously you could only enable probes in the core kernel.


  • Xtables: IPv4/IPv6 packet logging (xt_LOG) driver updated.

1.2 Xen Improvements

Block Frontend and Backend

  • Support for 'indirect-descriptors' allowing more throughput and lower latency.

  • Fixes from kernel versions 3.8 to 3.11.

Network Frontend and Backend

  • Support for IPv6 TCP GSO (Generic Segmentation Offload).

  • Switch to using NAPI + kthread 1:1 model to provide better scalability and performance.

  • Split of Tx (transmit) and Rx (receive) events.

  • Fixes from kernel versions 3.8 to 3.11.

VCPU Hotplug

  • Fixes from kernel versions 3.8 to 3.11.

1.3 Driver Updates

The Unbreakable Enterprise Kernel supports a wide range of hardware and devices. In close cooperation with hardware and storage vendors, several device drivers have been updated by Oracle.

1.3.1 Storage Adapter Drivers


  • NetXtreme II Fibre Channel over Ethernet (FCoE) driver (bnx2fc) updated to 2.4.1e.

  • NetXtreme II iSCSI driver (bnx2i) updated to


  • Cisco FCoE host bus adapter (HBA) driver (fnic) updated to


  • OneConnect (previously known as Blade Engine 2) Open-iSCSI driver (be2iscsi) updated to 10.0.659.0o.

  • LightPulse Fibre Channel SCSI (previously known as Fibre Channel HBA) driver (lpfc) updated to 0:


  • HP Smart Array CCISS driver (cciss) updated to 4.6.28-22.

  • HP Smart Array Controller driver (hpsa) updated to 3.4.2-5.


  • MegaRAID Serial Attached SCSI (SAS) driver (megaraid_sas) updated to 06.700.06.00-rc1.


  • Core services module driver (xscore) version 6.0.r7565 added. Required by all other Oracle Virtual Networking modules.

  • Virtual HBA driver (xsvhba) version 6.0.r7565 added.


  • Fibre Channel HBA driver (qla2xxx) updated to

  • iSCSI HBA driver (qla4xxx) updated to

1.3.2 Network Adapter Drivers


  • NetXtreme II 1 Gigabit network adapter driver (bnx2) updated to 2.2.4g.

  • NetXtreme II 10 Gigabit network adapter driver (bnx2x) updated to 1.78.80.

  • NetXtreme II Converged Network Interface Card core driver (cnic) updated to 2.5.18c.

  • Tigon3 Ethernet adapter driver (tg3) updated to 3.134f.


  • OneConnect (previously known as Blade Engine 2) 10Gbps adapter driver (be2net) updated to


  • PRO/1000 PCI Express Gigabit network adapter driver (e1000e) updated to 2.5.4-NAPI.

  • Gigabit Ethernet network adapter driver (igb) updated to 5.0.6.

  • 10 Gigabit PCI Express network adapter driver (ixgbe) updated to 3.18.7.

  • 10 Gigabit PCI Express Virtual Function driver (ixgbevf) updated to 2.11.3.


  • ConnectX Host Channel Adapter (HCA) Ethernet network adapter driver (mlx4_en) updated to 2.1.8.

  • The mlx4_vnic_helper driver has been removed as this functionality is now included with the mlx4_vnic driver.


  • Core services module driver (xscore) version 6.0.r7565 added. Required by all other Oracle Virtual Networking modules.

  • Virtual Ethernet driver (xve) version 6.0.r7565 added.

  • Virtual NIC driver (xsvnic) version 6.0.r7565 added.


  • NetXen Multi port (1/10) Gigabit Network Devices driver (netxen_nic) updated to 4.0.82.

  • 1/10 GbE Converged/Intelligent Ethernet Adapter driver (qlcnic) updated to

1.3.3 Miscellaneous Drivers


  • HP ProLiant Channel Interface Device Driver for Integrated Lights-Out (hpilo) updated to 1.4.1.

1.4 Technology Preview

The following features included in the Unbreakable Enterprise Kernel Release 3 are still under development, but are made available for testing and evaluation purposes.

  • DRBD (Distributed Replicated Block Device)

    A shared-nothing, synchronously replicated block device (RAID1 over network), designed to serve as a building block for high availability (HA) clusters. It requires a cluster manager (for example, pacemaker) for automatic failover.

  • Kernel module signing facility

    Applies cryptographic signature checking to modules on module load, checking the signature against a ring of public keys compiled into the kernel. GPG is used to do the cryptographic work and determines the format of the signature and key data.

  • Transcendent memory

    Transcendent Memory (tmem) provides a new approach for improving the utilization of physical memory in a virtualized environment by claiming underutilized memory in a system and making it available where it is most needed. From the perspective of an operating system, tmem is fast pseudo-RAM of indeterminate and varying size that is useful primarily when real RAM is in short supply. To learn more about this technology and its use cases, see the Transcendent Memory project page at

1.5 Compatibility

Oracle Linux maintains user-space compatibility with Red Hat Enterprise Linux, which is independent of the kernel version running underneath the operating system. Existing applications in user space will continue to run unmodified on the Unbreakable Enterprise Kernel Release 3 and no re-certifications are needed for RHEL certified applications.

To minimize impact on interoperability during releases, the Oracle Linux team works closely with third-party vendors whose hardware and software have dependencies on kernel modules. The kernel ABI for UEK R3 will remain unchanged in all subsequent updates to the initial release. In this release, there are changes to the kernel ABI relative to UEK R2 that require recompilation of third-party kernel modules on the system. Before installing UEK R3, verify its support status with your application vendor.

Chapter 2 Fixed and Known Issues

This chapter describes the fixed and known issues for the Unbreakable Enterprise Kernel Release 3.


Run the yum update command regularly to ensure that the latest bug fixes and security errata are installed on your system.

2.1 Fixed Issues

The following issues have been fixed in this update.


  • The usage message for the -c option to the btrfs qgroup limit command has been updated to make it clear that the quota limit is always enforced after compression and it is not possible to turn off this option. (Bug ID 16557528)

  • The btrfs receive command no longer causes an error when you retrieve data containing subvolumes. (Bug ID 17661845)

  • When you create a subdirectory in a directory that has the default ACLs (access control lists), the newly created subdirectory did not inherit the defaults from the parent. The ACLs are now applied correctly. (Bug ID 17669341)

  • Several performance and stability fixes. (Bug ID 17790692)

  • Due to the copy-on-write design of btrfs, snapshots can share the same data blocks. In UEK R3, sharing could be broken by defragmentation. This has been fixed. (Bug ID 18098511)


  • Support for SMB2 has been enabled in UEK R3. (Bug ID 17486287)


  • The vtimestamp() function now works correctly. The function keeps track of how much time a task has spent actually processing on a CPU. (Bug ID 17741477)

  • The SDT (Statically Defined Tracing) provider has been improved so that probes for kernel modules can now be enabled. Previously you could only enable probes in the core kernel. (Bug ID 17851716)

  • The dev_statname and dev_pathname in the devinfo_t structure now contains the correct information when the device is not partitioned. (Bug ID 17973698)


  • If an ext4 file system is full, preallocated space may not be writeable. (Bug ID 17347111)


  • The io_submit call is slow because it flushes writes. (Bug ID 14548775)


  • On an NFSv4 mount with delegations enabled, a file opened as RDWR and as RDONLY by several clients could cause a kernel crash when the state recovery process begins. (Bug ID 17931281)


  • The default coherency mount option is now buffered for better performance with direct I/O writes. Previously it was full. (Bug ID 17988729)


  • New files and directories created under the original directory now correctly inherit the group from the SGID group. (Bug ID 17354234)


  • The race condition between dentry put and lookup in configfs is fixed. (Bug ID 17931342)

2.2 Known Issues

This section describes the known issues in this update.


  • On some systems you might see ACPI-related error messages in dmesg similar to the following:

    ACPI Error: [CDW1] Namespace lookup failure, AE_NOT_FOUND
    ACPI Error: Method parse/execution failed [_SB_._OSC||\||]
    ACPI Error: Field [CDW3] at 96 exceeds Buffer [NULL] size 64 (bits)]]>

    These messages, which are not fatal, are caused by bugs in the BIOS. Contact your system vendor for a BIOS update. (Bug ID 13100702)

  • The following messages indicate that the BIOS does not present a suitable interface, such as _PSS or _PPC, that the acpi-cpufreq module requires:

    kernel: powernow-k8: this CPU is not supported anymore, using acpi-cpufreq instead.
    modprobe: FATAL: Error inserting acpi_cpufreq 

    There is no known workaround for this error. (Bug ID 17034535)


Calling the oracleasm init script, /etc/init.d/oracleasm, with the parameter scandisks can lead to error messages about missing devices similar to the following:

oracleasm-read-label: Unable to open device "device": No such file or directory

However, the device actually exists. You can ignore this error message, which is triggered by a timing issue. Only use the init script to start and stop the oracleasm service. All other options, such as scandisks, listdisk, and createdisk, are deprecated. For these and other administrative tasks, use /usr/sbin/oracleasm instead. (Bug ID 13639337)

bnx2x Driver

When using the bnx2x driver in a bridge, disable Transparent Packet Aggregation (TPA) by including the statement options bnx2x disable_tpa=1 in /etc/modprobe.conf. (Bug ID 14626070)


  • If you use the --alloc-start option with mkfs.btrfs to specify an offset for the start of the file system, the size of the file system should be smaller but this is not the case. It is also possible to specify an offset that is higher than the device size. (Bug ID 16946255)

  • The usage information for mkfs.btrfs reports raid5 and raid6 as possible profiles for both data and metadata. However, the kernel does not support these features and cannot mount file systems that use them. (Bug ID 16946303)

  • The btrfs filesystem balance command does not warn that the RAID level can be changed under certain circumstances, and does not provide the choice of cancelling the operation. (Bug ID 16472824)

  • Converting an existing ext2, ext3, or ext4 root file system to btrfs does not carry over the associated security contexts that are stored as part of a file's extended attributes. With SELinux enabled and set to enforcing mode, you might experience many permission denied errors after reboot, and the system might be unbootable. To avoid this problem, enforce automatic file system relabeling to run at bootup time. To trigger automatic relabeling, create an empty file named .autorelabel (for example, by using touch) in the file system's root directory before rebooting the system after the initial conversion. The presence of this file instruct SELinux to recreate the security attributes for all files on the file system. If you forget to do this and rebooting fails, either temporarily disable SELinux completely by adding selinux=0 to the kernel boot parameters, or disable enforcing of the SELinux policy by adding enforcing=0. (Bug ID 13806043)

  • Commands such as du can show inconsistent results for file sizes in a btrfs file system when the number of bytes that is under delayed allocation is changing. (Bug ID 13096268)

  • The copy-on-write nature of btrfs means that every operation on the file system initially requires disk space. It is possible that you cannot execute any operation on a disk that has no space left; even removing a file might not be possible. The workaround is to run sync before retrying the operation. If this does not help, remount the file system with the -o nodatacow option and delete some files to free up space. See

  • Btrfs has a limit of 237 or fewer hard links to a file from a single directory. The exact limit depends on the number of characters in the file name. The limit is 237 for a file with up to eight characters in its file name; the limit is lower for longer file names. Attempting to create more than this number of links results in the error Too many links. You can create more hard links to the same file from another directory. Although the limitation of the number of hard links in a single directory has been increased to 65535, the version of mkfs.btrfs that is provided in the btrfs-progs package does not yet support the compatibility flag for this feature. (Bug ID 16285431)

  • If you run the btrfs quota enable command on a non-empty file system, any existing files do not count toward space usage. Removing these files can cause usage reports to display negative numbers and the file system to be inaccessible. The workaround is to enable quotas immediately after creating the file system. If you have already written data to the file system, it is too late to enable quotas. (Bug ID 16569350)

  • The btrfs quota rescan command is not currently implemented. The command does not perform a rescan and returns without displaying any message. (Bug ID 16569350)

  • When you overwrite data in a file, starting somewhere in the middle of the file, the overwritten space is counted twice in the space usage numbers that btrfs qgroup show displays. (Bug ID 16609467)

  • If you run btrfsck --init-csum-tree on a file system and then run a simple btrfsck on the same file system, the command displays a Backref mismatch error that was not previously present. (Bug ID 16972799)

  • Btrfs tracks the devices on which you create btrfs file systems. If you subsequently reuse these devices in a file system other than btrfs, you might see error messages such as the following when performing a device scan or creating a RAID-1 file system, for example:

    ERROR: device scan failed '/dev/cciss/c0d0p1' - Invalid argument

    You can safely ignore these errors. (Bug ID 17087097)

  • If you use the -s option to specify a sector size to mkfs.btrfs that is different from the page size, the created file system cannot be mounted. By default, the sector size is set to be the same as the page size. (Bug ID 17087232)

  • In some cases, it is possible to run the btrfs-convert command on a mounted file system. This may result in unexpected behaviour and can possibly cause a kernel panic. Make sure to unmount a file system before converting it to Btrfs. (Bug ID 18061751)

  • The btrfs subvolume delete command may result in a "Directory not empty" error. This error message is incorrect. The actual reason that the subvolume cannot be deleted is that the subvolume is configured as the default subvolume. The default subvolume is the subvolume that is mounted when no subvolume is specified with the mount command. Before you can delete the subvolume, you need to configure a different default subvolume using the btrfs subvolume set-default command. (Bug ID 17661944)

CPU Microcode Update Failures on PVM or PVHVM Guests

When running Oracle Linux 6 with UEK R3, you might see error messages in dmesg or /var/log/messages similar to this one:

microcode: CPU0 update to revision 0x6b failed.

You can ignore this warning. You do not need to upgrade the microcode for virtual CPUs as presented to the guest. (Bug ID 12576264, 13782843)

DHCP Lease is not Obtained at Boot Time

If DHCP lease negotiation takes more than 5 seconds at boot time, the following message is displayed:

ethX: failed. No link present. Check cable?

If the ethtool ethX command confirms that the interface is present, edit /etc/sysconfig/network-scripts/ifcfg-ethX and set LINKDELAY=N, where N is a value greater than 5 seconds (for example, 30 seconds). Alternatively, use NetworkManager to configure the interface. (Bug ID 16620177)

dm-nfs Module Obsolete

In UEK R2, the dm-nfs module provided the ability to create a loopback device for a mounted NFS file or file system. For example, the feature allowed you to create the shared storage for an Oracle 3 VM cluster on an NFS file system. The dm-nfs module provided direct I/O to the server and bypassed the loop driver to avoid an additional level of page caching. The dm-nfs module is not provided with UEK R3. The loop driver can now provide the same I/O functionality as dm-nfs by extending the AIO interface to perform direct I/O. To create the loopback device, use the losetup command instead of dmsetup.


  • Using kill -9 to terminate dtrace can leave breakpoints outstanding in processes being traced, which might sooner or later kill them.

  • Argument declarations for probe definitions cannot be declared with derived types such as enum, struct, or union.

  • The following compiler warning can be ignored for probe definition arguments of type string (which is a D type but not a C type):

    provider_def.h:line#: warning: parameter names (without types) in function declaration

ERST Message

You can safely ignore the following message that might be displayed in syslog or dmesg:

ERST: Failed to get Error Log Address Range.

The message indicates that the system BIOS does not support an Error Record Serialization Table (ERST). (Bug ID 17034576)

ext4 Inline Data

The inline data feature that allows the data of small files to be stored inside their inodes is not yet available. The -O inline_data option to the mkfs.ext4 and tune2fs commands is not supported. (Bug ID 17210654)

Firmware Warning Message

You can safely ignore the following firmware warning message that might be displayed on some Sun hardware:

[Firmware Warn]: GHES: Poll interval is 0 for generic hardware error source:
1, disabled.

(Bug ID 13696512)

Huge Pages

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)

I/O Scheduler

The Unbreakable Enterprise Kernel uses the deadline scheduler as the default I/O scheduler. For the Red Hat Compatible Kernel, the default I/O scheduler is the cfq scheduler.

ioapic Failure Messages

You can safely ignore messages such as ioapic: probe of 0000:00:05.4 failed with error -22. Such messages are the result of the ioapic driver attempting to re-register I/O APIC PCI devices that were already registered at boot time. (Bug ID 17034993)

InfiniBand Warning Messages When Disabling a Switch Port

You might see the following warning messages if you use the ibportstate disable command to disable a switch port:

ibwarn: [2696] _do_madrpc: recv failed: Connection timed out
ibwarn: [2696] mad_rpc: _do_madrpc failed; dport (Lid 38)
ibportstate: iberror: failed: smp set portinfo failed

You can safely ignore these warnings. (Bug ID 16248314)

IPoIB Mode Switching

The Internet Protocol over InfiniBand (IPoIB) driver supports the use of either connected mode or datagram mode with an interface, where datagram mode is the default mode. Changing the mode of an InfiniBand interface by echoing either connected or datagram to /sys/class/net/ibN/mode is not supported. It is also not possible to change the mode of an InfiniBand interface while it is enabled.

To change the IPoIB mode of an InfiniBand interface:

  1. Edit the /etc/sysconfig/network-scripts/ifcfg-ibN configuration file, where N is the number of the interface:

    • To configure connected mode, specify CONNECTED_MODE=yes in the file.

    • To configure datagram mode, either specify CONNECTED_MODE=no in the file or do not specify this setting at all (datagram mode is enabled by default).


    Before saving your changes, make sure that you have not specified more than one setting for CONNECTED_MODE in the file.

  2. To enable the specified mode on the interface, use the following commands to take down the interface and bring it back up:

    # ifdown ibN
    # ifup ibN

(Bug ID 17479833)

Linux Containers (LXC)

  • The correct operation of containers might require that you completely disable SELinux on the host system. For example, SELinux can interfere with container operation under the following conditions:

    • Running the halt or shutdown command from inside the container hangs the container or results in a permission denied error. (An alternate workaround is to use the init 0 command from inside the container to shut it down.)

    • Setting a password inside the container results in a permission denied error, even when run as root.

    • You want to allow ssh logins to the container.

    To disable SELinux on the host:

    1. Edit the configuration file for SELinux, /etc/selinux/config and set the value of the SELINUX directive to disabled.

    2. Shut down and reboot the host system.

  • The root user in a container can affect the configuration of the host system by setting some /proc entries. (Bug ID 17190287)

  • Using yum to update packages inside the container that use init scripts can undo changes made by the Oracle template.

  • Migrating live containers (lxc-checkpoint) is not yet supported.

  • 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)

NUMA Warning Messages on a Non-NUMA System

You can safely ignore the following warning messages in dmesg and /var/log messages if you see them on a non-NUMA system:

kernel: NUMA: Warning: node ids are out of bound, from=-1 to=-1 distance=10
hcid[4293]: Register path:/org/bluez fallback:1
kernel: No NUMA configuration found

(Bug ID 13711370)

pcspkr Driver Error Message

You can safely ignore the following error message:

Error: Driver 'pcspkr' is already registered, aborting...

The message arises from an alias conflict between snd-pcsp and pcspkr. To prevent the message from being displayed, add the following line to /etc/modprobe.d/blacklist.conf:

blacklist snd-pcsp

(Bug ID 10355937)

Power/Level is Deprecated Message (libfprint)

The following message might appear in dmesg or /var/log/messages:

WARNING! power/level is deprecated; use power/control instead.

The USB subsystem in UEK R3 deprecates the power/level sysfs attribute in favor of the power/control attribute. The libfprint fingerprinting library triggers this warning via udev rules that try to use the old attribute first. You can safely ignore this warning. The setting of the appropriate power level still succeeds. (Bug ID 13523418)

RDMA Does Not Load the mlx4_ib Module

If you enable the OFED stack and the RDMA service but the version of the RDMA package is lower than rdma‑3.10‑3.0.2.el6, the RDMA service does not load the mlx4_ib module automatically.

To configure the RDMA service to load the mlx4_ib module at boot time:

  1. Edit /etc/rdma/rdma.conf and set the entry MLX4_LOAD=yes in this file.

  2. To make the change take effect, restart the RDMA service or reboot the system.

sched_yield() Settings for CFS

For the Unbreakable Enterprise Kernel, kernel.sched_compat_yield=1 is set by default. For the Red Hat Compatible Kernel, kernel.sched_compat_yield=0 is used by default.

Slow Performance With Multipath Devices

Starting with UEK R2, the device mapper has had the capability to check whether the underlying storage device has advertised the need to flush the data that resides in the device's cache to its non-volatile storage. For a data integrity operation, such as fsync and sync, the operation will now need to include the time to flush the device's cache (if it is advertised). Such an operation will appear to be slower when compared to a previous older kernel, however this is the correct behavior. (Bug ID 17823743)

Soft Lockup Errors When Booting

When upgrading or installing the UEK R3 kernel on fast hardware, usually with SAN storage attached, the kernel can fail to boot and BUG: soft lockup messages are displayed in the console log. The workaround is to increase the baud rate from the default value of 9600 by amending the kernel boot line in /boot/grub/grub.conf to include an appropriate console setting, for example:


A value of 115200 is recommended as smaller values such as 19200 are known to be insufficient for some systems (for example, see If the host implements an integrated system management infrastructure, such as ILOM on Sun and Oracle systems or iLO on HP systems, configure the integrated console baud rate to match the setting for the host system. Otherwise, the integrated console is likely to display garbage characters. (Bug ID 17064059, 17252160)

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.


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

(Bug ID 16823432)

User Namespaces

The kernel functionality (CONFIG_USER_NS) that allows unprivileged processes to create namespaces for users inside which they have root privileges is not currently implemented because of a clash with the implementation of XFS. This functionality is primarily intended for use with Linux Containers. As a result, the lxc-checkconfig command displays User namespace: missing. (Bug ID 16656850)


  • When booting UEK R3 as a PVHVM guest, you can safely ignore the following kernel message:

    register_vcpu_info failed:

    (Bug ID 13713774)

  • Under Oracle VM Server 3.1.1, migrating a PVHVM guest that is running the UEK R3 kernel causes a disparity between the date and time as displayed by date and hwclock. The workaround post migration is either to run the command hwclock --hctosys on the guest or to reboot the guest. (Bug ID 16861041)

  • On virtualized systems that are built on Xen version 3, including all releases of Oracle VM 2 including 2.2.2 and 2.2.3, disk synchronization requests for ext3 and ext4 file systems result in journal corruption with kernel messages similar to the following being logged:

    blkfront: barrier: empty write xvda op failed
    blkfront: xvda: barrier or flush: disabled

    In addition, journal failures such as the following might be reported:

    Aborting journal on device xvda1

    The workaround is to add the mount option barrier=0 to all ext3 and ext4 file systems in the guest VM before upgrading to UEK R3. For example, you would change a mount entry such as:

    UUID=4e4287b1-87dc-47a8-b69a-075c7579eaf1  /  ext3  defaults  1 1

    so that it reads:

    UUID=4e4287b1-87dc-47a8-b69a-075c7579eaf1  /  ext3  defaults,barrier=0  1 1

    This issue does not apply to Xen 4 based systems, such as Oracle VM 3. (Bug ID 17310816)

X.509 Certificates for Module Verification

The system reports a message similar to the following if there is a problem loading an in-kernel X.509 module verification certificate at boot time:

Loading module verification certificates 
X.509: Cert 0c21da3d73dcdbaffc799e3d26f3c846a3afdc43 is not yet valid 
MODSIGN: Problem loading in-kernel X.509 certificate (-129)

This error occurs because the hardware clock lags behind the system time as shown by hwclock, for example:

# hwclock
Tue 20 Aug 2013 01:41:40 PM EDT -0.767004 seconds

The solution is to set the hardware clock from the system time by running the following command:

# hwclock --systohc

After correcting the hardware clock, no error should be seen at boot time, for example:

Loading module verification certificates 
MODSIGN: Loaded cert 'Slarti: Josteldalsbreen signing key: 

(Bug ID 17346862)

Chapter 3 Installation and Availability

You can install Unbreakable Enterprise Kernel Release 3 (UEK R3) on Oracle Linux 6 Update 4 or newer, running either the Red Hat compatible kernel or a previous version of the Unbreakable Enterprise Kernel. If you are still running an older version of Oracle Linux, first update your system to the latest available update release.

UEK R3 is supported on the x86-64 architecture but not on x86.

The kernel's source code is available via a public git source code repository at

Starting with Oracle Linux 6 Update 5 for x86-64, UEK R3 is the default boot kernel for fresh installations of Oracle Linux.

For systems that are running UEK R3 and are subscribed to the ol6_x86_64_UEKR3_latest channel on ULN, or the ol6_UEKR3_latest repository in the Oracle Public Yum repository, you upgrade to the latest UEK release as follows:

  1. Upgrade all packages on the system, including kernel packages.

    # yum update

    By default, the boot manager automatically enables the most recent kernel version so you do not need to change your GRUB configuration.

  2. Reboot the system.

    # shutdown -r now

For systems that are currently running a previous version of the Unbreakable Enterprise Kernel (UEK R2) or the Red Hat compatible kernel (RHCK), you can switch to UEK R3 at any time. For details, see:

3.1 Switching a System to UEK R3 (ULN)

If you have a subscription to Oracle Unbreakable Linux support, you can obtain the packages for Unbreakable Enterprise Kernel Release 3 (UEK R3) by registering your system with the Unbreakable Linux Network (ULN) and subscribing it to additional channels.

Before you begin:

To Switch a System to UEK R3:

  1. Using a browser, log in at with the ULN user name and password that you used to register the system.

  2. On the Systems tab, click the link named of your system in the list of registered machines.

  3. On the System Details page, click Manage Subscriptions.

  4. On the System Summary page, select each required channel in the Available Channels list and click the right arrow to move the channel to the Subscribed Channels list.

    The kernel image and user-space packages are available on the following ULN channels:

    Channel Name

    Description and Channel Label


    Oracle Linux 6 Latest (x86_64)

    All packages released for Oracle Linux 6 (x86_64) including the latest errata packages. (x86_64).



    Unbreakable Enterprise Kernel Release 3 for Oracle Linux 6 (x86_64) - Latest

    Latest packages for Unbreakable Enterprise Kernel Release 3 for Oracle Linux 6 (x86_64).

    Contains the kernel-uek*, dtrace-modules-*, libdtrace-*, and uname26 packages.



    Oracle Linux 6 Dtrace Userspace Tools (x86_64) - Latest

    The latest DTrace userspace tools for Oracle Linux 6 (x86_64).

    Contains the dtrace-utils* packages.



    OFED supporting tool packages for Unbreakable Enterprise Kernel on Oracle Linux 6 (x86_64)

    Latest OpenFabrics Enterprise Distribution (OFED) supporting tools for the Unbreakable Enterprise Kernel (UEK) on Oracle Linux 6 (x86_64).



    HA Utilities for MySQL and Oracle Linux 6 (x86_64)

    Management Utilities for MySQL HA with Oracle Linux 6.

    Contains the drbd84-utils package.



    As a minimum, you should subscribe the system to the ol6_x86_64_latest and the ol6_x86_64_UEKR3_latest channels. If required, you can also add the channels for the DTrace, OFED, and DRBD packages.


    Take care not to select the ol6_x86_64_UEK_BETA channel.

    Because you are switching to the latest UEK kernel, you no longer need to subscribe the system to the previous UEK R2 (ol6_x86_64_UEK_latest) channel.

  5. When you have finished selecting channels, click Save Subscriptions and log out of ULN.

  6. Log in as root on the system.

  7. Upgrade all packages on the system, including kernel packages.

    # yum update

    By default, the boot manager automatically enables the most recent kernel version so you do not need to change your GRUB configuration.

  8. Reboot the system.

    # shutdown -r now

3.2 Switching a System to UEK R3 (Public Yum)

If your system is not registered with ULN, you can obtain most of the packages for Unbreakable Enterprise Kernel Release 3 (UEK R3) from Oracle Public Yum by subscribing it to additional repositories.

Before you begin:

  • Check that the system meets the requirements for installing UEK R3.

    For details, see Chapter 3, Installation and Availability.

  • Remove some of the existing OpenFabrics Enterprise Distribution (OFED) packages.

    You only need to do this if you have installed any OFED packages on your system and you want to replace them with the latest OFED tools packages. The packages have to be removed manually, see Section 3.3, “Upgrading OFED Packages”.

To Switch a System to UEK R3:

  1. Log in as root on the system.

  2. Change directory to /etc/yum.repos.d.

    # cd /etc/yum.repos.d

    This assumes that yum on your system is configured to find repository files in the default /etc/yum.repos.d directory.

  3. Download the Oracle Linux 6 repository configuration file,

    For example:

    # wget

    The /etc/yum.repos.d directory is updated with the repository configuration file.

  4. Enable the required repositories by editing the public-yum-ol6.repo file.

    You enable or disable repositories in the file by setting the value of the enabled directive to 1 or 0 as required.

    The kernel image and user-space packages are available on the following Oracle Public Yum repositories:

    Channel Label




    All packages released for Oracle Linux 6 (x86_64) including the latest errata packages.



    Latest packages for Unbreakable Enterprise Kernel Release 3 for Oracle Linux 6.

    Contains the kernel-uek*, dtrace-modules-*, libdtrace-*, and uname26 packages.



    Latest OpenFabrics Enterprise Distribution (OFED) supporting tools for the Unbreakable Enterprise Kernel (UEK) on Oracle Linux 6 (x86_64).


    As a minimum, you should enable the ol6_latest and the ol6_UEKR3_latest repositories.


    The DTrace utility and DRBD packages are not available on Public Yum.

    Because you are switching to the latest UEK kernel, you can disable the previous UEK R2 (ol6_UEK_latest) repository.

    In the following example, the ol6_UEKR3_latest repository is enabled, and the ol6_UEK_latest repository is disabled:

    name=Latest Unbreakable Enterprise Kernel for Oracle Linux $releasever ($basearch)
    name=Latest Unbreakable Enterprise Kernel for Oracle Linux $releasever ($basearch)
  5. Upgrade all packages on the system, including kernel packages.

    # yum update

    By default, the boot manager automatically enables the most recent kernel version so you do not need to change your GRUB configuration.

  6. Reboot the system.

    # shutdown -r now

3.3 Upgrading OFED Packages

If you have enabled the ol6_ofed_UEK channel, you must remove any existing OFED packages for the 32-bit x86 architecture before you can upgrade the remaining OFED packages on your system. You must also completely remove and reinstall the ibutils packages. The latest version of the ibutils package no longer depends on an ibutils-libs package as the libraries are now included in ibutils itself.

Use the following command to remove any non-upgradable packages for the x86 architecture:

# rpm -e infiniband-diags-1.5.12-5.el6.i686 \
libibcm-1.0.5-3.el6.i686 \
libibcm-devel-1.0.5-3.el6.i686 \
libibmad-1.3.9-1.el6.i686 \
libibmad-devel-1.3.9-1.el6.i686 \
libibumad-1.3.8-1.el6.i686 \
libibumad-devel-1.3.8-1.el6.i686 \
libibverbs-1.1.6-5.el6.i686 \
libibverbs-devel-1.1.6-5.el6.i686 \
libmlx4-1.0.4-1.el6.i686 \
librdmacm-1.0.17-0.git4b5c1aa.el6.i686 \
librdmacm-devel-1.0.17-0.git4b5c1aa.el6.i686 \
opensm-devel-3.3.15-1.el6.i686 \
opensm-libs-3.3.15-1.el6.i686 \

Use the following commands to remove the existing ibutils and ibutils-libs packages and install the new ibutils package:

# rpm -e ibutils-1.5.7-7.el6.x86_64 \
# yum install ibutils