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 and 7 on the x86-64 architecture. It is based on the mainline Linux kernel version 3.8.13.

The 3.8.13-98 release is the sixth 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

  • Support for installing and using Oracle Linux on systems that have enabled UEFI Secure Boot. A system in Secure Boot mode will load only boot loaders and kernels that have been signed by Oracle.

  • Virtual eXtensible Local Area Network (VXLAN) and Generic Routing Encapsulation (GRE) support added to the UEK Open Vswitch kernel module (kmod-openvswitch-uek).

  • Support for Intel Sandy Bridge memory controllers enabled.

  • Cisco SCSI NIC driver (snic) version added.

  • Enabled hardware support for the SGI UltraViolet 3 platform.

  • Kernel modules are now signed using the SHA-512 hash algorithm (previously SHA-256 was used).

  • Enabled support for more than eight PTP hardware clocks (PHC).

  • Bug fixes for btrfs, ext4, xfs, and OCFS2 file systems.

  • Bug fixes to support Oracle Linux guests running on Microsoft Azure or Hyper-V.

This kernel update also includes updated dependencies for QLogic firmware. The dependencies should be resolved when you install the new kernel.

1.2 LXC Improvements

With version 1.0.7 and later of the Linux Containers (lxc) package under UEK R3 QU6, you can adjust the values of the following kernel parameters under the /proc hierarchy in an Oracle Linux container if you specify the --privileged option to the lxc-oracle template script:

  • /proc/sys/kernel/msgmax

  • /proc/sys/kernel/msgmnb

  • /proc/sys/kernel/sem

  • /proc/sys/kernel/shmall

  • /proc/sys/kernel/shmmax

  • /proc/sys/kernel/shmmni

  • /proc/sys/net/ipv4/conf/default/accept_source_route

  • /proc/sys/net/ipv4/conf/default/rp_filter

  • /proc/sys/net/ipv4/ip_forward

Each of these parameters can have a different value than that configured for the host system and for other containers running on the host system. The default value is derived from the template when you create the container. Oracle recommends that you change a setting only if the Oracle database or other application requires a value other than the default for a container.

The --privileged option also adds the CAP_SYS_NICE capability, which allows you to set negative nice values (that is, more favored for scheduling) for processes from within the container.

Prior to UEK R3 QU6, the following host-only parameters were not visible within the container due to kernel limitations:

  • /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

  • /proc/sys/net/ipv4/tcp_syncookies

With UEK R3 QU6 and later, these parameters are read-only within the container to allow Oracle Database and other applications to be installed. You can change the values of these parameters only from the host. Any changes that you make to host-only parameters apply to all containers on the host.

For more information, see Configuring Kernel Parameters and Resource Limits in the Oracle Database 11.2 Quick Installation Guide, Configuring Kernel Parameters and Resource Limits in the Oracle Database 12.1 Quick Installation Guide, Linux Containers in Oracle® Linux 6: Administrator's Solutions Guide, and Linux Containers in Oracle® Linux 7: Administrator's Guide.

(Bug ID 21267882)

1.3 Xen Improvements

  • Prevent soft lockups due to long-running hypercalls.

  • Rewrite of the Physical to Machine (P2M) table to lower SWIOTLB usage.

  • Fixed memory leaks in the Xen block driver.

  • Fixed compound pages that were not handled in the xen-netfront driver.

1.4 DTrace Improvements

DTrace Kernel Modules (Version 0.4.5)

New Features and Changes
  • You can now use User-Level Statically Defined Tracing (USDT) probes in 32-bit applications on 64-bit hosts.

  • The d_path() D subroutine requires its argument to be a pointer to a path structure that corresponds to a file that is known to the current task.

Fixed Bugs
  • A minor memory leak with the DTrace help tracing facility has been fixed. When the dtrace.ko module was loaded, a buffer (by default 64K) was allocated and never released.

  • Stack backtraces are more accurate as a result of various fixes to adjust the number of frames to skip for specific probes.

  • The stack depth was being determined by requesting a backtrace to be written into a temporary buffer that was being allocated (vmalloc), which posed significant problems when probes were executing in a context that does not support memory allocations. The buffer is now obtained from the scratch area of memory that DTrace provides for probe processing.

  • A system crash could occur if you passed an invalid pointer to d_path(). Due to its implementation, it is not possible to depend on safe memory accesses to avoid this. Now you must validate the pointer before calling d_path().

DTrace User Space Tools (Version 0.4.6)

New Features and Changes
  • The dtrace-utils-devel package now requires the corresponding version of the dtrace-utils package.

  • The dtrace-utils package has been renamed.

  • There is a new dtrace -vV option which reports information on the released version of DTrace, as well as the internal ID of dtrace(1) and libdtrace(1).

  • The <dtrace.h> header file can be included to support development of DTrace consumer applications.

  • DTrace only loads D libraries from directories with a name that corresponds to the current running kernel.

Fixed Bugs
  • Processes that receive SIGTRAP during normal operation now work even when being traced. Previously, the SIGTRAP was ignored.

  • DTrace no longer loses track of processes that perform exec() while DTrace is examining their dynamic linker state.

  • DTrace no longer leaves breakpoints in forked processes.

  • DTrace no longer considers that it knows the state of the symbol table of processes it has stopped monitoring.

  • DTrace no longer crashes multi-threaded processes that use dlopen() or dlclose().

1.5 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.

Table 1.1 Updated Drivers in UEK R3 QU6








SCSI driver




NetXtreme II 1 Gigabit network adapter driver




NetXtreme II FCoE driver



NetXtreme II iSCSI driver




NetXtreme II 10 Gigabit network adapter driver




NetXtreme II converged NIC core driver



FCoE HBA driver



SCSI NIC driver



OneConnect (Blade Engine 2) NIC driver




LightPulse Fibre Channel SCSI driver




Ethernet Connection XL710 network driver




XL710 X710 virtual function network driver




10 Gigabit PCI Express network driver




10 Gigabit PCI Express virtual function network driver




NVM Express device driver



Fibre channel HBA driver



iSCSI HBA driver



PVSCSI driver



Virtual machine communication interface



Virtual socket family

1.6 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. Do not use these features on production systems.

  • 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.

  • NFS over RDMA Client

    Enables you to use NFS over the RDMA transport on the Oracle InfiniBand stack. This is more efficient than using the TCP/IPoIB transport. The technology preview does not include NFS over RDMA server support, or support for NFS over RDMA in virtualized environments. NFS version 3 and 4 are supported. Currently, only the Mellanox ConnectX-2 and ConnectX-3 Host Channel Adapters (HCAs) are supported. The client passes the full Connectathon NFS test suite using these HCAs. The Release Notes will be updated if additional adapters are supported after the initial release.

    See Section 1.6.1, “Using the NFS over RDMA Client” for details of how to use the feature.

  • Swap files on NFS shares

    Ability for a system to use swap files that reside on NFS shares. For information about using swap files, see the swapon(8) manual page and the Administrator's Guide for your Oracle Linux release.

  • 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

1.6.1 Using the NFS over RDMA Client

The following instructions also include details for enabling an NFS over RDMA server. These are provided as an example only, as the NFS over RDMA server is currently not supported with the UEK R3 kernel.

  1. Install an RDMA device, set up InfiniBand and enable IPoIB.

    The Oracle Linux OFED packages are available from the following channels:

    • Oracle Linux 6: ol6_x86_64_ofed_UEK

    • Oracle Linux 7: ol7_x86_64_UEKR3_OFED20

  2. Check that the RDMA device is working.

    # cat /sys/class/infiniband/driver_name/ports/1/state
    4: ACTIVE

    where driver_name is the RDMA device driver, for example mlx4_0.

  3. Verify the physical InfiniBand interfaces and links.

    Check that the hosts can be contacted through the InfiniBand switch, by using commands such as ibhosts, and ibnetdiscover.

  4. Check the connection between the NFS client and NFS server.

    You can configure the settings for an InfiniBand interface in the
    /etc/sysconfig/network-scripts/ifcfg-ibN file.

    You can use the ping command to check the connection. For example:

    nfs-server$ ip addr add dev ib0
    nfs-client$ ip addr add dev ib0
    nfs-server$ ping 
    nfs-client$ ping
  5. Install the nfs-utils package on the NFS client and server.

  6. Configure the NFS shares.

    Edit the /etc/exports file. Define the directories that the NFS server will make available for clients to mount, using the IPoIB addresses of the clients. For example:

  7. On the NFS server, load the svcrdma kernel module and start the NFS service.

    Oracle Linux 6:

    # modprobe svcrdma
    # service nfs start
    # echo rdma 20049 > /proc/fs/nfsd/portlist

    Oracle Linux 7:

    # modprobe svcrdma
    # systemctl start nfs-server
    # echo rdma 20049 > /proc/fs/nfsd/portlist

    The rdma 20049 setting does not persist when the NFS service is restarted. You have to set it each time the NFS service starts.

  8. On the NFS client, load the xprtrdma kernel module and start the NFS service.

    # modprobe xprtrdma
    # service nfs start
    # mount -o proto=rdma,port=20049 host:/export /mnt 

    where host is the host name or IP address of the IPoIB server, and export is the name of the NFS share.

    To check that the mount over RDMA is successful, check the proto field for the mount point.

    # nfsstat -m
    /mnt from
    Flags: rw,relatime,vers=4.0,rsize=262144,wsize=262144,namlen=255,hard,proto=rdma,port=20049,


    # cat /proc/mounts

Known Issues

Any mounted file systems must be unmounted on the NFS client before you shut down the NFS server. Otherwise the NFS server hangs when you shut down.

1.7 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.

1.8 Header Packages for Development

The kernel-headers packages provide the C header files that specify the interface between user-space binaries or libraries and UEK or RHCK. These header files define the structures and constants that you need to build most standard programs or to rebuild the glibc package.

The kernel-devel and kernel-uek-devel packages provide the kernel headers and makefiles that you need to build modules against UEK and RHCK.

To install the packages required to build modules against UEK and the C header files for both UEK and RHCK:

# yum install kernel-uek-devel-`uname -r` kernel-headers