Chapter 23. Kernel

Red Hat Enterprise Linux 7.2 introduces the criu tool as a Technology Preview. This tool implements Checkpoint/Restore in User-space, which can be used to freeze a running application and store it as a collection of files. Later, the application can be restored from its frozen state.

The criu tool depends on Protocol Buffers, a language-neutral, platform-neutral extensible mechanism for serializing structured data. The protobuf and protobuf-c packages, which provide this dependency, are also added to Red Hat Enterprise Linux 7.2 as a Technology Preview.

This feature provides additional security to servers running Linux containers by providing better isolation between the host and the containers. Administrators of a container are no longer able to perform administrative operations on the host, which increases security.

An enhanced watchdog driver for IBM System z is available as a Technology Preview. This driver supports Linux logical partitions (LPAR) as well as Linux guests in the z/VM hypervisor, and provides automatic reboot and automatic dump capabilities if a Linux system becomes unresponsive.

The most common type of reset that the Virtual Function (VF) encounters is a Physical Function (PF) reset that cascades down into a VF reset for each VF. However, for 'bigger' resets, such as a Core or EMP reset, when the device is reinitialized, the VF previously did not get the same VSI, so the VF was not able to recover, as it continued to request resources for its original VSI. As a Technology Preview, this update adds an extra state to the admin queue state machine, so that the driver can re-request its configuration information at runtime. During reset recovery, this bit is set in the aq_required field, and the configuration information is fetched before attempting to bring the driver back up.

Intel® Omni-Path Architecture (OPA) kernel driver, which is supported as a Technology Preview, provides Host Fabric Interconnect (HFI) hardware with initialization and setup for high performance data transfers (high bandwidth, high message rate, low latency) between compute and I/O nodes in a clustered environment.

For instructions on how to obtain Intel® Omni-Path documentation, see https://access.redhat.com/articles/2039623.

As a Technology Preview, Red Hat Enterprise Linux 7.2 introduces support for the Diag0c feature on IBM System z. Diag0c support makes it possible to read the CPU performance metrics provided by the z/VM hypervisor, and allows obtaining the management time for each online CPU of a Linux guest where the diagnose task is executed.

As a Technology Preview, Red Hat Enterprise Linux 7.2 includes the 10GbE RDMA over Converged Ethernet (RoCE) Express feature. This makes it possible to use Ethernet and Remote Direct Memory Access (RDMA), as well as the Direct Access Programming Library (DAPL) and OpenFabrics Enterprise Distribution (OFED) APIs, on IBM System z.

Before using this feature on an IBM z13 system, ensure that the minimum required service is applied: z/VM APAR UM34525 and HW ycode N98778.057 (bundle 14).

Red Hat Enterprise Linux 7.2 includes the Generic Workqueue (GenWQE) engine device driver as a Technology Preview. The initial task of the driver is to perform zlib-style compression and decompression of the RFC1950, RFC1951 and RFC1952 formats, but it can be adjusted to accelerate a variety of other tasks.

The kexec system call has been provided as a Technology Preview. This system call enables loading and booting into another kernel from the currently running kernel, thus performing the function of the boot loader from within the kernel. Hardware initialization, which is normally done during a standard system boot, is not performed during a kexec boot, which significantly reduces the time required for a reboot.