With Unbreakable Enterprise Kernel Release 5 Update 3, Oracle continues to deliver kernel modifications to enable support for 64-bit Arm (aarch64) architecture. These changes are built and tested against existing Arm hardware and provide support for Oracle Linux for Arm. Features described in this document are available for Arm insofar as the hardware is capable of supporting the feature that is described. Limitations and items that are beyond the scope of current development work for Arm are described in more detail in Unusable or Unavailable Features for Arm.

Significant improvements have been made to a number of drivers, through vendor contributions, for better support on embedded 64-bit Arm platforms.

UEK R5U3 provides equivalent core kernel functionality to UEK R5U2, making use of the same upstream mainline kernel release, with additional patches to enhance existing functionality and provide some minor bug fixes and security improvements. Key changes are specific to functionality that is required for Oracle Database and other Oracle software.

On-Demand-Paging (ODP) is a virtual memory management technique to ease memory registration. Applications do not need to map the underlying physical pages of the address space, and track the validity of the mappings. Instead, the HCA (Host Channel Adapter) requests the latest mappings from the operating system when pages are not present, and the operating system invalidates mappings which are no longer valid due to either non-present pages or mapping changes.

A large number of kernel updates have been implemented in this update release to enhance, improve, and fix ODP functionality for InfiniBand devices so that it can be used with Oracle Database.

The following notable updates have been implemented for file system functionality in UEK R5U3:

• XFS

  A deadlock bug that caused the file system to freeze lock and not release has been fixed. This issue was resolved by implementing an inode deactivation feature and by updating code to flag inodes that should be deactivated. This feature allows memory to be freed so that the lock can be released.

  A fix was also applied for an issue where XFS would not unlock when a chgrp operation failed on account of being out of disk quota. The missing unlock facility was added to the code.

• CIFS

  An upstream patch was applied to resolve an issue that could cause POSIX lock leakages and system crashes. The patch causes the system to ignore any unlock errors in cifs_lock() that are flagged with the FL_CLOSE hint and relies on the client and server to handle these when closing.

Remote Direct Memory Access (RDMA) is a feature that allows direct memory access between two systems that are connected by a network. RDMA facilitates high-throughput and low-latency networking in clusters.

Unbreakable Enterprise Kernel Release 5 Update 3 includes RDMA features that are provided in the upstream kernel, with the addition of Ksplice and DTrace functionality and Oracle's own RDMA features, which includes support for RDS and Shared-PD.

Notable changes to the RDMA implementation in UEK R5U3 include the following:

• Fix to resilient_rdmaip for race condition

  A race condition that was introduced into the active-active bonding code to facilitate resilient_rdmaip is resolved.