Chapter 11. Kernel

The /proc/pid/cmdline file length is now unlimited

The /proc/pid/cmdline file length limit for the ps command was previously hard-coded in the kernel to 4096 characters. This update makes sure the length of /proc/pid/cmdline is unlimited, which is especially useful for listing processes with long command line arguments. (BZ#1100069)

Support for LSO and LRO

This update adds support for Large Send Offload (LSO) and Large Receive Offload (LRO) to the PowerVM virtual Ethernet driver (ibmveth). The enhancement allows you to enable LRO on the Shared Ethernet Adapter (SEA) in a mixed AIX and Linux Central Electronics Complex (CEC), allowing better networking performance and better interoperability with AIX in a shared ethernet adapter environment. (BZ#1233272)

ipr rebased to version 2.6.3

The ipr driver has been upgraded to upstream version 2.6.3, which provides a number of enhancements and bug fixes over the previous version. Namely, the update enables new SAS VRAID adapters on IBM Power Systems and includes recent performance improvements. As a result, the update improves disk performance and supports recent adapters on IBM Power Systems. (BZ#1252713)

ixgbe rebased to version 4.2.1

The ixgbe NIC driver has been upgraded to upstream version 4.2.1, which provides a number of bug fixes and enhancements over the previous version. Notably:
  • Null pointer crashes related to VLAN support have been fixed.
  • Two more devices from the Intel X550 Ethernet controller family are now supported: IDs 15AC and 15AD have been added.
  • Several PHY-related problems have been addressed: link disruptions and link flapping.
  • Added PHY-related support for Intel X550.
  • Performance has been improved. (BZ#1249244)

L2 cache information is gathered using the CPUID instruction

With this update, Level 2 (L2) processor cache information such as the base cache or the number of cache leaves is gathered using the CPUID instruction. (BZ#987679)

bnx2 rebased to version 2.2.6

The bnx2 NIC driver has been upgraded to upstream version 2.2.6, which provides a number of bug fixes and enhancements over the previous version. Notably:
  • Bandwidth allocation for some MF modes has been fixed.
  • Toggling of rxvlan can now be disabled.
  • A chip initialization bug has been fixed.
  • Inconsistent use of page sizes has been fixed. (BZ#1252124)

e100 rebased to version 3.5.24-k2-NAPI

The e100 NIC driver has been upgraded to upstream version 3.5.24-k2-NAPI, which provides a number of bug fixes over the previous version. Notably, the update adds error checking around DMA mapping to avoid resource leaks and fixes a possible NULL pointer dereference during initialization. (BZ#1150338)

e1000e rebased to version 3.2.6-k

The e1000e driver has been upgraded to upstream version 3.2.6-k, which provides a number of bug fixes over the previous version. Notably, the new version prevents possible data corruption and enables both ULP and EEE in Sx mode. (BZ#1249241)

MLDv1 and MLDv2 snooping added to bridge

With this update, the bridge module adds support to IPv6 multicast by snooping for MLDv1 and MLDv2. Now, IPv6 multicast messages are sent only to ports with subscribed multicast receivers. (BZ#587714)

perf has been updated

To support a greater range of hardware and incorporate numerous bug fixes, perf has been updated. Notable enhancements include:
  • Added support for additional model numbers of 5th Generation Intel Core i7 processors.
  • Added support for Intel Xeon v5 mobile and desktop processors.
  • Enabled support for the uncore subsystem for Intel Xeon v3 and v4 processors.
  • Enabled support for the uncore subsystem for Intel Xeon Processor D-1500. (BZ#1216217)

EDAC support for Intel Xeon v4

The kernel has been updated to incorporate new code that adds EDAC (Error Detection and Correction) support for the Xeon v4 memory controllers from Intel. (BZ#1245372)

Crash dump performance enhancements

The time taken to complete a crash dump on systems with large quantities of memory has been reduced in kexec-tools and makedumpfile by making use of mmap() to remove empty and unneeded pages. (BZ#1097904)

Interval Tree Support for Intel Xeon v3 and v4 core processors with Gen graphics

To enable access to the GPU functionality of some Intel processors without recompiling a custom kernel, Interval Tree support has been added. (BZ#1251197)

CPU microcode update for Intel processors

The kernel has been updated to contain the latest microcode definitions for all Intel processors. This is the latest update from Intel at the time of publishing and is designated version 20151106. (BZ#1244968)

Minimal support for secondary endpoints with nf_conntrack_proto_sctp

Basic multihoming support has been added to Stream Control Transmission Protocol (SCTP), allowing traffic between secondary endpoints to pass through where it would previously be classified as invalid and blocked by most common firewall configurations. (BZ#1267612)

The sch_qfq scheduler now supports QFQ+

The sch_qfq scheduler now supports the Quick Fair Queuing Plus (QFQ+) algorithm, which improves the scheduler's efficiency and accuracy. At the same time, a number of bug fixes have been applied to further improve the behavior of sch_qfq under various conditions. (BZ#1152235)

Tracking and capturing I/O statistics for the tape driver is available

It is now possible to track and capture I/O performance statistics, and measure tape device performance. The user can use the statistics exposed in the /sys/class/scsi_tape/ tree with custom tools. (BZ#875277)

mpt2sas and mpt3sas merged

The source codes of mpt2sas and mpt3sas drivers have been merged. Unlike in upstream, Red Hat Enterprise Linux 6 continues to maintain two binary drivers for compatibility reasons. (BZ#717090)

Firmware-assisted Crash Dumping

Red Hat Enterprise Linux 6.8 introduces support for firmware-assisted dump (fadump), which provides an alternative dumping mechanism to kdump. Fadump is supported only on PowerPC architecture. The goal of fadump is to enable the dump of a crashed system, and to do so from a fully-reset system, and to minimize the total elapsed time until the system is back in production use. Fadump is integrated with kdump infrastructure present in the user space to seemlessly switch between kdump and fadump mechanisms. (BZ#1254923)

Setting an SELinux context label for a block device

To be able to label device nodes, most commonly disks, as used by certain applications, this update provides the possibility to apply SELinux labels on device nodes created by udev. The system administrator can set a new option to give a label to a newly created device node as follows:
SECLABEL{selinux}="label"
(BZ#1015300)

New packages: libevdev

The libevdev packages have been added to Red Hat Enterprise Linux 6.8. These packages contain a library to wrap kernel evdev devices and provide a proper API to interact with these devices. (BZ#1250806)

lpfc driver update

With the latest update, LPE31000, LPE32000 HBAs, and all HBA variants of this architecture now detect and enable both Broadcom-ECD certified SFP and QSFP optics. For firmware rev 11.0.204.0 and later, unqualified optics are disabled, the network link shows link down state, and an error message is logged to the log file.
The lpfc driver in Red Hat Enterprise Linux 6.8 displays the following message and the network link does not come up:
3176 Misconfigured Physical Port - Port Name [wwpn] Unknown event status [status]
The users are recommended to use only Broadcom-ECD certified SFP and QSFP optics. If any of the 3176 messages are seen in the logs and the link does not come up, contact Broadcom-ECD technical support. (BZ#1295468)