6.2 Release Notes
Release Notes for Red Hat Enterprise Linux 6.2
Edition 2
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Abstract
Red Hat Enterprise Linux minor releases are an aggregation of
individual enhancement, security and bug fix errata. The Red Hat
Enterprise Linux 6.2 Release Notes documents the major changes made to
the Red Hat Enterprise Linux 6 operating system and its accompanying
applications for this minor release. Detailed notes on all changes in
this minor release are available in the
Technical Notes.
The Release Notes provide high level coverage of the improvements and
additions that have been implemented in Red Hat Enterprise Linux 6.2.
For detailed documentation on all changes to Red Hat Enterprise Linux
for the 6.2 update, refer to the
Technical Notes.
Refer to the
Online Release Notes for the most up-to-date version of the Red Hat Enterprise Linux 6.2 Release Notes.
Chapter 1. Hardware Support
The biosdevname package has been upgraded to version 0.3.8, providing the --smbios and --nopirq
command line parameters. With theses command line parameters, source
code patches, which removed these codepaths, can be removed from the
build process.
In Red Hat Enterprise Linux 6.2, the compression format used for the initrd.img file has changed. The image is now compressed using LZMA rather than Gzip.
To decompress an image, use the xz -d command. For example:
~]# xz -dc initrd.img | cpio -id
To compress an image, use the xz -9 --format=lzma command. For example:
~]# find . | cpio -c -o | xz -9 --format=lzma > initrd.img
Fibre Channel and Serial Attach SCSI (SAS) devices can be now
specified by a World Wide Name (WWN) or a World Wide Identifier (WWID)
for unattended installations. WWN is part of the IEEE standard which
makes it easier to identify storage devices during installation for
users utilizing Storage Area Networks (SAN) and other advanced network
topologies. When a storage device is attached to a server using multiple
physical paths for redundancy or improved performance, WWN for any of
these paths is sufficient to identify the device.
The initial ramdisk file on 64-bit PowerPC and 64-bit IBM POWER Series systems is now named initrd.img. In previous releases, it was named ramdisk.image.gz.
In Red Hat Enterprise Linux 6.2, a static IPv6 address can be specified for the ipv6 boot option for network installations. The specified address must be of the following form:
<IPv6 address>[/<prefix length>]
An example of a valid IPv6 address would then be 3ffe:ffff:0:1::1/128. If the prefix is omitted, the value of 64 is assumed. Specifying a static IPv6 address for the ipv6 boot option complements the already existing dhcp and auto parameters that can be specified for the ipv6 boot option.
The kernel shipped in Red Hat Enterprise Linux 6.2 includes several
hundred bug fixes for and enhancements to the Linux kernel. For details
concerning every bug fixed in and every enhancement added to the kernel
for this release, refer to the kernel section of the
Red Hat Enterprise Linux 6.2 Technical Notes.
Prior to Red Hat Enterprise Linux 6.2, the qla4xxx adapter firmware managed discovery and login to iSCSI targets. A new feature in Red Hat Enterprise Linux 6.2 allows you to use open-iscsi to manage the qla4xxx discovery and login process. This can result in a more uniform management process.
This new feature is enabled by default. The qla4xxx iSCSI firmware settings are accessible via:
~]# iscsiadm -m fw
This feature may be disabled by setting the module ql4xdisablesysfsboot=1 parameter as follows:
Set the parameter in the /etc/modprobe.d file:
~]# echo "options qla4xxx ql4xdisablesysfsboot=1" >> /etc/modprobe.d/qla4xxx.conf
Reload the qla4xxx module either by executing the following set of commands:
~]# rmmod qla4xxx
~]# modprobe qla4xxx
or, if you are booted off the qla4xxx device, by rebooting your system.
When booted off a
qla4xxx device,
upgrading from Red Hat Enterprise Linux 6.1 to Red Hat Enterprise Linux
6.2 will cause the system to fail to boot up with the new kernel. For
more information on this known issue, refer to the
Technical Notes.
Kdump (a kexec-based crash dumping mechanism) now supports dumping of
the core on the following file systems on Red Hat Enterprise Linux 6:
The pkgtemp module has been merged with the coretemp module. The pkgtemp module is now deprecated. The coretemp module now supports all the features it previously did plus the features that were supported by the pkgtemp module.
The coretemp previously only provided per core temperatures, while the pkgtemp module provided the temperatures of the CPU package. In Red Hat Enterprise Linux 6.2, the coretemp module allows you to read the temperatures for of the cores, the uncore, and the package.
It is advisable to adjust any scripts using either of these modules.
In Red Hat Enterprise Linux 6.2, the SCSI midlayer supports optional lockless dispatching of SCSI driver queuecommand functions.
This is a backport of the upstream SCSI lock pushdown commit. The
backport retains binary compatibility with Red Hat Enterprise Linux 6.0
and Red Hat Enterprise Linux 6.1. Retaining binary compatibility
requires divergence from the equivalent upstream SCSI lock pushdown
mechanism.
A previously unused flag in the scsi_host_template structure is used by SCSI drivers to indicate to the SCSI midlayer that driver queuecommand will be dispatched without the SCSI host bus lock held.
The default behavior is that the Scsi_Host lock will be held during a driver queuecommand dispatch. Setting the scsi_host_template lockless bit prior to scsi_host_alloc will cause the driver queuecommand function to be dispatched without the Scsi_Host lock being held. In such a case, the responsibility for any lock protection required is pushed down into the driver queuecommand code path.
SCSI Drivers updated to use lockless queuecommand in Red Hat Enterprise Linux 6.2 are listed below:
iscsi_iser
be2iscsi
bnx2fc
bnx2i
cxgb3i
cxgb4i
fcoe (software fcoe)
qla2xxx
qla4xxx
Red Hat Enterprise Linux 6.2 includes support for Fiber Channel over Ethernet (FCoE) target mode, as a Technology Preview. This kernel feature is configurable via targetadmin, supplied by the fcoe-target-utils package. FCoE is designed to be used on a network supporting Data Center Bridging (DCB). Further details are available in the dcbtool(8) and targetadmin(8) man pages.
This feature uses the new SCSI target layer, which falls under this
Technology Preview, and should not be used independently from the FCoE
target support. This package contains the AGPL license.
The mdadm and mdmon
utilities have been updated to support Array Auto-Rebuild, RAID Level
Migrations, RAID 5 support limitation, and SAS-SATA drive roaming.
Red Hat Enterprise Linux 6.2 supports merging of flush requests to assist devices which are slow to perform a flush.
Red Hat Enterprise Linux 6.2 adds UV2 Hub support. UV2 is the UVhub
chip that is the successor to the current UV1 hub chip. UV2 uses the
HARP hub chip that is currently in development. UV2 provides support for
new Intel sockets. It provides new features to improve performance. UV2
is being designed to support 64 TB of memory in an SSI.
Additionally, the node controller MMRs have been updated for UV systems.
Red Hat Enterprise Linux 6.2 introduces the acpi_rsdp
boot parameter for kdump to pass an ACPI RSDP address, so that the
kdump kernel can boot without EFI (Extensible Firmware Interface).
The following enhancements have been added to the QETH network device driver:
Support for af_iucv HiperSockets transport
Support for forced signal adapter indications
Support for asynchronous delivery of storage blocks
New Ethernet Protocol ID added to the if_ether module
Support for the new CPACF (CP Assist for Cryptographic Function)
algorithms, supported by IBM zEnterprise 196, has been added. The new
hardware accelerated algorithms are:
CTR mode for AES
CTR mode for DES and 3DES
XTS mode for AES with key lengths of 128 and 256 bits
GHASH message digest for GCM mode
Red Hat Enterprise Linux 6.2 supports conditional resource-reallocation through the pci=realloc
kernel parameter. This feature provides an interim solution for adding a
dynamic reallocate pci resource without causing any regressions. It
disables dynamic reallocation by default, but adds the ability to enable
it through the pci=realloc kernel command line parameter.
Dynamic reallocation is disabled by default. It can be enabled with the pci=realloc kernel command line parameter. In addition, bridge resources have been updated to provide larger ranges in the PCI assign unassigned call.
Red Hat Enterprise Linux 6.2 enables SMEP (Supervision Mode Execution
Protection) in the kernel. SMEP provides an enforcement mechanism,
allowing the system to set a requirement that is not intended to be
executed from user pages while in the supervisor mode. This requirement
is then enforced by the CPU. This feature is able to prevent all attacks
irrespective of the vulnerability in the system code that are executed
from user mode pages while the CPU is in the supervisor mode.
Support for enhanced fast string REP MOVSB/STORESB instructions for the latest Intel platform has been added.
The USB 3.0 xHCI host side driver has been updated to add split-hub
support, allowing the xHCI host controller to act as an external USB 3.0
hub by registering a USB 3.0 roothub and a USB 2.0 roothub.
The ACPI, APEI, and EINJ parameter support is now disabled by default.
Red Hat Enterprise Linux 6.2 adds support for pstore—a file system interface for platform dependent persistent storage.
Support for printk based APEI (ACPI Platform Error Interface)
hardware error reporting has been added, providing a way to unify errors
from various sources and send them to the system console.
The ioatdma driver (dma engine driver) has been updated to support Intel processors with a dma engine.
Support for the Digi/IBM PCIe 2-port Async EIA-232 Adapter has been
added to the 8250 PCI serial driver. Additionally, EEH (Enhanced Error
Handling) support for the Digi/IBM PCIe 2-port Async EIA-232 Adapter has
been added to the 8250 PCI serial driver.
ARI (Alternative Routing- ID Interpretation) support, a PCIe v2 feature, has been to Red Hat Enterprise Linux 6.2.
PCIe OBFF (Optimized Buffer Flush/Fill) enable/disable support has
been added for Intel's latest platform. OBFF provides devices with
information on interrupts and memory activity and their potentially
reduced power impact, ultimately improving energy efficiency.
In Red Hat Enterprise Linux 6.2, the kernel is enabled to capture kernel oops/panic reports from the dmesg buffer into NVRAM on PowerPC architectures.
The MXM driver, responsible for handling graphics switching on NVIDIA
platforms, has been backported to Red Hat Enterprise Linux 6.2.
Red Hat Enterprise Linux 6.2 introduces page coalescing, a feature on
IBM Power servers which allows for coalescing identical pages between
logical partitions.
Support for L3 Cache Partitioning has been added to the latest AMD family CPUs.
The thinkpad_acpi module has been updated to add support for new ThinkPad models.
Latest Intel processor C-State support has been added to intel_idle.
Red Hat Enterprise Linux 6.2 now displays warnings for IOMMU (Input/Output Memory Management Unit) on AMD systems.
Logging of board, system, and BIOS information to dmesg during boot has been added.
cputable entries have been added to the kernel, providing support for the latest IBM PowerPC processor family.
The VPHN (Virtual Processor Home Node) feature has been disabled on IBM System p.
The following drivers are now supported by the latest Intel chipset:
On IBM PowerPC systems, the exec-shield value in sysctl or in the /proc/sys/kernel/exec-shield parameter is no longer enforced.
Additional checks and fixes have been added to support kdump on 64-bit PowerPC and 64-bit IBM POWER Series systems.
The UV MMTIMER module (uv_mmtimer) has been enabled on SGI platforms. The uv_mmtimer module allows direct userland access to the UV system's real time clock which is synchronized across all hubs.
Support for the IB700 module has been added in Red Hat Enterprise Linux 6.2
The aer_mask_override module
parameter has been added, providing a way to override the corrected or
uncorrected masks for a PCI device. The mask will have the bit
corresponding to the status passed into the aer_inject() function.
USB 3.0 host controller support has been added to 64-bit PowerPC and 64-bit IBM POWER Series systems.
An improved upstreamed OOM (Out of Memory) killer implementation has
been backported to Red Hat Enterprise Linux 6.2. The improvements
include:
Processes which are about to exit are preferred by the OOM killer.
The OOM kill process also kills the children of the selected processes.
Heuristic have been added to kill the forkbomb processes.
The oom_score_adj /proc tunable parameter adds the value stored in each process's oom_score_adj variable, which can be adjusted via /proc. This allows for an adjustment of each process's attractiveness to the OOM killer in user space; setting it to -1000 will disable OOM kills entirely, while setting to +1000 is marking this process as OOM's primary kill target.
Red Hat Enterprise Linux 6.2 provides an updated zram driver (creates generic RAM based compressed block devices).
In Red Hat Enterprise Linux 6.2, the taskstat utility (prints ASET tasks status) in the kernel has been enhanced by providing microsecond CPU time granularity for the top utility to use.
Added cgroup support
Added handling of /proc/sys/kernel/kptr_restrict
Added more cache-miss percentage printouts
Added the -d -d and -d -d -d options to show more CPU events
Added the --sync/-S option
Added support for the PERF_TYPE_RAW parameter
Added more documentation about the -f/--fields option
The python-perf package has been added for python binding support.
Red Hat Enterprise Linux 6.2 adds OProfile support for the latest Intel processors.
The number of interrupt requests (IRQ) is now counted in a sum of all irq counter, reducing the cost of the look-up in the /proc/stat file.
Red Hat Enterprise Linux 6.2 introduces a scheduling improvement
where a hint is provided to the scheduler on the next buddy hint on
sleep and preempt path. This hint/enhancement helps the workload of
multiple tasks in multiple task groups.
In Red Hat Enterprise Linux 6.2, Transparent Huge Pages are now supported in several places of the kernel:
The system calls of mremap, mincore, and mprotect
/proc tunable parameters: /proc/<pid>/smaps and /proc/vmstat
Additionally, Transparent Huge Pages add some compaction improvements.
Red Hat Enterprise Linux 6.2 adds XTS (XEX-based Tweaked CodeBook) AES256 self-tests to meet the FIPS-140 requirements.
Previously, the SELinux netfilter hooks returned NF_DROP if they dropped a packet. In Red Hat Enterprise Linux 6.2, a drop in the netfilter
hooks is signaled as a permanent fatal error and is not transient. By
doing this, the error is passed back up the stack, and in some places
and applications will get a faster interaction that something went
wrong.
In Red Hat Enterprise Linux 6.2, the remount mount options (mount -o remount) are passed to a new LSM hook.
Red Hat Enterprise Linux 6.0 and 6.1 defaulted to running UEFI
systems in a physical addressing mode. Red Hat Enterprise Linux 6.2
defaults to running UEFI systems in a virtual addressing mode. The
previous behavior may be obtained by passing the physefi kernel parameter.
In Red Hat Enterprise Linux 6, the default core_collector method for kdumping the core over SSH has been changed from scp to makedumpfile, which helps shrink the size of the core file when copying over the network link, resulting in faster copying.
If you require the old vmcore full size core file, specify the following in the /etc/kdump.conf file:
core_collector /usr/bin/scp
Chapter 4. Resource Management
The Completely Fair Scheduler (CFS) in the Linux kernel is a
proportional share scheduler which divides the CPU time proportionately
between groups of tasks depending on the priority/weight of the task or
shares assigned to groups of tasks. In CFS, a task group can get more
than its share of CPU if there are enough idle CPU cycles available in
the system, due to the work conserving nature of the scheduler.
However there are enterprise scenarios listed below, where giving more
than the desired CPU share to a task group is not acceptable:
- Pay-per-use
In enterprise systems that cater to multiple customers, cloud
service providers need to assign a fixed amount of CPU time to the
virtual guest based on the service level.
- Service level guarantees
Customer demands a percentage of CPU resource without service interruptions for each virtual guest.
In these scenarios, the scheduler needs to put a hard stop on the CPU
resource consumption of a task group if it exceeds a preset limit. This
is usually achieved by throttling the task group when it fully consumes
its allocated CPU time.
The cgroups CPU ceiling enforcement is considered a very important
addition to the Red Hat Enterprise Linux feature repertoire, for the use
case listed above. The CPU ceiling enforcement is provided by the
Credit Scheduler in Xen, and also in the VMware ESX scheduler.
Red Hat Enterprise Linux 6 enabled cgroups out of the box, and libvirt
created a cgroups per guest model. On large SMP systems, an increase in
the number of cgroups, worsened the performance. However, in Red Hat
Enterprise Linux 6.2, the cgroups CPU scalability has been significantly
improved, making it possible to create and run several hundreds of
cgroups at once with no performance implications.
In addition to the scalability improvement, a /proc tunable parameter, dd sysctl_sched_shares_window, has been added, with the default is set to 10 ms.
The cgroups I/O controller design has improved to reduce the usage of
locks inside the I/O controller, resulting in improved performance.
Also, the I/O controller now supports per cgroup statistics.
Red Hat Enterprise Linux 6.2 introduces the memory usage overhead
improvement on the memory controller by reducing allocation overhead for
page_cgroup array by 37%. Additionally, the direct page_cgroup-to-page pointer has been removed, improving performance of the memory controller.
The default for CFQ's group_isolation variable has been changed from 0 to 1 (/sys/block/<device>/queue/iosched/group_isoaltion). After various testing and numerous user reports, it was found that having default 1 is more useful. When set to 0,
all random I/O queues become part of the root cgroup and not the actual
cgroup which the application is part of. Consequently, this leads to no
service differentiation for applications.
Chapter 5. Device Drivers
The lpfc driver for Emulex Fibre Channel Host Bus Adapters has been updated to version 8.3.5.45.2p.
The mptfusion driver has been updated to version 3.4.19.
The bnx2fc for the Broadcom Netxtreme II 57712 chip has been updated to version of 1.0.4.
The qla2xxx driver for QLogic Fibre Channel HBAs has been updated to version to 8.03.07.05.06.2-k.
The megaraid driver has been updated to version v5.38.
The arcmsr driver for Areca RAID controllers has been updated.
The beiscsi driver has been updated to version 2.103.298.0.
The ipr driver for IBM Power Linux RAID SCSI HBAs has been updated to version 2.5.2.
The cciss driver has been updated to provide a fix for cciss driver kdump failures.
The hpsa driver has been updated to provide a fix for hpsa driver kdump failures.
The bnx2i driver for Broadcom
NetXtreme II iSCSI has been updated to version 2.7.0.3 to support the
578xx family of Multi-Port Single-Chip 10G Ethernet Converged
Controllers.
The mpt2sas driver has been updated to version 09.101.00.00.
The Brocade BFA FC SCSI driver (bfa driver) has been updated to version 2.3.2.4.
The be2iscsi driver for ServerEngines BladeEngine 2 Open iSCSI devices has been updated to version 4.0.160r.
The ata_generic driver has been updated to add Intel IDE-R ATA support.
The isci driver has been updated to version 2.6.40-rc.
The libfc, libfcoe, and fcoe drivers have been updated.
The qib driver TrueScale HCAs has been updated.
The libata module has been updated to include improved error handling.
The md driver has been updated to include dm-raid target, which provides improved RAID capabilities through a DM interface. The dm-raid code is currently marked as a Technology Preview.
Device Mapper support has been updated to upstream version 3.1+.
Application support for the qla4xxx using bsg/netlink interfaces has been added.
The DIF/DIX kernel code has been updated to the latest upstream version, affecting scsi, block, and dm/md.
The netxen driver for NetXen Multi port (1/10) Gigabit Network devices to version 4.0.75.
The vmxnet3 driver has been updated.
The bnx2x driver has been updated to version v1.70.
The be2net driver for ServerEngines BladeEngine2 10Gbps network devices has been updated to version 4.0.100u.
The ixgbevf driver has been updated to version 2.1.0-k
The cxgb4 driver for Chelsio Terminator4 10G Unified Wire Network Controllers has been updated.
The cxgb3 driver for the Chelsio T3 Family of network devices has been updated.
The ixgbe driver for Intel 10 Gigabit PCI Express network devices is updated to version 3.4.8-k.
The e1000e driver for Intel PRO/1000 network devices has been updated to version 1.3.16-k.
The e1000 driver for Intel PRO/1000 network devices has been updated, providing support for Marvell Alaska M88E1118R PHY.
The e100 driver has been updated.
The enic driver for Cisco 10G Ethernet devices has been updated to version 2.1.1.24.
The igbvf driver has been updated to version 2.0.0-k.
The igb driver for Intel Gigabit Ethernet Adapters has been updated.
The bnx2 driver for the NetXtreme II 1 Gigabit Ethernet controllers has been updated to version 2.1.6+.
The tg3 driver for Broadcom Tigon3 ethernet devices has been updated to version 3.119.
The qlcnic driver for the HP NC-Series QLogic 10 Gigabit Server Adapters has been updated to version 5.0.16+.
The bna driver has been updated.
The r8169 driver has been updated to fix two bugs related to Rx checksum offloading.
The qlge driver has been updated to version v1.00.00.29.
The cnic driver has been updated to
add iSCSI and FCoE support for the 578xx family of Multi-Port
Single-Chip 10G Ethernet Converged Controllers, VLAN support, and new bnx2x firmware interface.
The iwl6000 and iwlwifi have been update with the EEPROM version 0x423.
The radeon driver has been updated with post-3.0 fixes, including backported drm/agp code.
The nouveau and i915 drivers have been updated, including backported drm/agp code.
The Ricoh memory stick driver (R5C592) has been update with new KFIFO application programming interface.
The netjet driver has been updated to blacklist the Digium TDM400P PCI Card.
The lm78 driver has been updated.
The wacom driver has been updater to add support for the Cintiq 21UX2, Intuos4 WL, and DTU-2231 adapter cards.
The synaptics driver has been updated to add multi-touch support.
The ALSA HDA audio driver has been updated to enable or improve support for new chipsets and HDA audio codecs.
The edac driver has been updated to support the new Northbridge chip for AMD platforms.
The iprutils package provides utilities to manage and configure SCSI devices that are supported by the ipr SCSI storage device driver. The iprutils package has been updated to support SAS VRAID functions for new 6 GB SAS adapters on IBM POWER7.
In Red Hat Enterprise Linux 6.2, support for MD's RAID personalities has been added to LVM as a Technology Preview.
The following basic features are available: create, display, rename,
use, and remove RAID logical volumes. Automated fault tolerance is not
yet available.
It is possible to create RAID logical volumes by specifying the --type <segtype> argument. The following are a few examples:
Create a RAID1 array (this is a different implementation of RAID1 than LVM's mirror segment type):
~]# lvcreate --type raid1 -m 1 -L 1G -n my_lv my_vg
Create a RAID5 array (3 stripes + 1 implicit parity):
~]# lvcreate --type raid5 -i 3 -L 1G -n my_lv my_vg
Create a RAID6 array (3 stripes + 2 implicit parity):
~]# lvcreate --type raid6 -i 3 -L 1G -n my_lv my_vg
iSER initiator and target is now fully supported. Red Hat Enterprise
Linux can now function as an iSCSI initiator and storage server in
production environments that use InfiniBand and where high throughput
and low latency are key requirements.
LVM devices can now be activated or deactivated quicker than before.
This is relevant to high-density environments that involve a large
number of LVM configurations. An example of this is a host that supports
hundreds of virtual guests each using one or more logical volumes.
The XFS file system is currently supported in Red Hat Enterprise
Linux 6 and is well suited for very large files and file systems on a
single host. Integrated backup and restore, direct I/O and online
resizing of the file system are some of the benefits that this file
system provides.
The XFS implementation has been improved to better handle metadata
intensive workloads. An example of this type of workload is accessing
thousands of small files in a directory. Prior to this enhancement,
metadata processing could cause a bottleneck and lead to degraded
performance. To address this problem an option to delay the logging of
the metadata has been added that provides a significant performance
improvement. As a result of this delayed logging of metadata, XFS
performance is on par with ext4 for such workloads. The default mount
options have also been updated to use delayed logging.
Parallel NFS (pNFS) is a part of the NFS v4.1 standard that allows
clients to access storage devices directly and in parallel. The pNFS
architecture eliminates the scalability and performance issues
associated with NFS servers in deployment today.
pNFS supports 3 different storage protocols or layouts: files, objects
and blocks. The Red Hat Enterprise Linux 6.2 NFS client supports the
files layout protocol.
To automatically enable the pNFS functionality, create the /etc/modprobe.d/dist-nfsv41.conf file with the following line and reboot the system:
alias nfs-layouttype4-1 nfs_layout_nfsv41_files
Now when the -o minorversion=1 mount option is specified, and the server is pNFS-enabled, the pNFS client code is automatically enabled.
The CIFS (Common Internet File System) protocol allows for a unified
way to accessing remote files on disparate operating systems. The CIFS
client has traditionally only allowed for synchronous writes. This meant
that the client process would not yield back control until the writes
were successfully completed. This can lead to degraded performance for
large transactions that take long to complete. The CIFS client has been
updated to write data in parallel without the need to wait for the
sequential writes. This change can now result in performance
improvements up to 200%.
Support for NTLMSSP authentication has been added to CIFS. In addition, CIFS now uses the kernel's crypto API.
The autofs4 module has been updated to kernel version 2.6.38.
Fixed tracepoints have been added to ext3 and jbd.
Support for the -o nobarrier mount option in ext4, and its utilities: tune2fs, debugfs, libext2fs, has been added.
Red Hat Enterprise Linux 6.2 introduces the multi-message send system call which is the send version of the existing recvmmsg system call in Red Hat Enterprise Linux 6.
The system call sendmmsg socket API looks like this:
struct mmsghdr {
struct msghdr msg_hdr;
unsigned msg_len;
};
ssize_t sendmmsg(int socket, struct mmsghdr *datagrams, int vlen, int flags);
Red Hat Enterprise Linux 6.2 includes Transmit Packet Steering (XPS)
for multiqueue devices. XPS introduces more efficient transmission of
network packets for multiqueue devices by specifically targeting the
processor involved in sending the packet. XPS enables the selection of
the transmit queue for packet transmission based on configuration. This
is analogous to the receive-side functionality implemented in Red Hat
Enterprise Linux 6.1 which allowed for processor selection based on the
receive queue (RPS). XPS has shown to improve throughput by 20% to 30%.
Previously, the bridge flooded packets to unregistered groups to all
ports. However, this behavior is not desirable in environments where
traffic to unregistered groups is always present. In Red Hat Enterprise
Linux 6.2, traffic is only sent to unregistered groups to ports marked
as routers. To force flooding to any given port, mark that port as a
router.
Red Hat Enterprise Linux 6.2 adds support for SCTP multihoming—the
ability of nodes (that is, multi-home nodes) to be reached under several
IP addresses.
In Red Hat Enterprise Linux 6.2, more tracepoints have been added for
UDP packet drop events. These tracepoints provide a way to analyze the
reasons why UDP packets are dropped.
The IPSet feature in the kernel has been added to store multiple IP
addresses or port numbers, and match them against a collection via iptables.
The TCP initial receive window default has been increased from
4 kB to 15 kB. The benefit of this increase is that any data
(15 kB > payload > 4 kB) can now fit in the initial
window. With a 4 kB setting (IW3), any payload larger than
4 kB would have to be broken into multiple transfers.
GSO (Generic Segmentation Offload) support for the IPv6 forward path
has been added, improving the performance of host/guest communication if
GSO is enabled.
vios-proxy is a
stream-socket proxy for providing connectivity between a client on a
virtual guest and a server on a Hypervisor host. Communication occurs
over virtio-serial links. This feature is introduced as a Technology
Preview in Red Hat Enterprise Linux 6.2.
Chapter 9. Authentication and Interoperability
Red Hat Enterprise Linux 6.2 includes identity management
capabilities that allow for central management of user identities,
policy-based access control and authentication services. This identity
management service, previously referred to as IPA, is based on the open
source FreeIPA project. These services have been present as a Technology
Preview in previous Red Hat Enterprise Linux 6 releases. With this
release, identity management has been promoted to fully supported.
The
Identity Management Guide
provides detailed information about the Identity Management solution,
the technologies with which it works, and some of the terminology used
to describe it. It also provides high-level design information for both
the client and server components.
Support for smart cards with a PIV (Personal Identity Verification)
interface has been added in Red Hat Enterprise Linux 6.2. It is now
possible to use FIPS 201 compliant PIV cards that allow for secure use
of data. PIV cards enable confidentiality of data by restricting access
to the card holder. They also ensure data integrity by allowing only the
card holder to make modifications. They guarantee the authenticity of
the information and prevent non-repudiation of data. The use of PIV
cards is mandated via the U.S. Homeland Security Presidential Directive
12 (HSPC-12) which requires the use of this type of technology to gain
access to all government IT systems.
The new subscription management platform delivers Red Hat
subscriptions and software services in a flexible, scalable and secure
way. When installing a new Red Hat Enterprise Linux 6 system, a user
receives X.509 certificates which contain information about which Red
Hat products are installed and what subscriptions the machine is
consuming. The subscription information includes support levels,
expiration dates, Red Hat account numbers, and Red Hat contract numbers.
In addition, an X.509 certificate allows a machine to authenticate to
the Red Hat Content Delivery Network (CDN). The globally distributed Red
Hat Content Delivery Network (CDN) is designed to work even with an
outage of the Red Hat systems. Users outside of North America should see
improved update speeds and availability with the new system. RHN
Classic continues to be the default option for computer registration and
for receiving updates.
Red Hat customer portal, in a conjunction with new functionality
available in Red Hat Enterprise Linux 6.2, allows customers to register
and subscribe up to 25 machines that are completely disconnected. Prior
to this enhancement, customers with disconnected systems were not able
to receive benefits from subscription information and tracking from the
RHN website. For customers with more than 25 disconnected machines, RHN
Satellite continues to be a recommended option at additional cost.
In Red Hat Enterprise Linux 6.2, during system registration, the Red Hat Subscription Manager is now used by default.
Chapter 11. Security, Standards and Certification
As of Red Hat Enterprise Linux 6.2 Beta, Red Hat Enterprise Linux 6
is under evaluation for Common Criteria at Evaluation Assurance Level
(EAL) 4+. Common Criteria provides a standardized way of expressing
security requirements and defines a set of rigorous criteria by which
products are evaluated.
As of Red Hat Enterprise Linux 6.2 Beta, Red Hat Enterprise Linux 6
cryptographic modules are under evaluation for FIPS-140 certification.
FIPS-140 is a U.S. government security standard used for accrediting
cryptographic modules. Red Hat Enterprise Linux now satisfies the
regulatory requirement mandated by the U.S. federal government for
acceptable use of cryptographic modules by all the governmental
agencies.
Red Hat Enterprise Linux 6.2 includes Intel Trusted Boot, a trusted boot mechanism (provided by the tboot
package). Trusted boot is an install-time optional component that
allows for Intel's Trusted Execution Technology (TXT) to perform a
measured and verified launch of the operating system kernel. Trusted
boot is supported on both Intel x86 and Intel 64 architectures.
Chapter 12. Compiler and Tools
SystemTap is a tracing and probing tool that allows users to study
and monitor the activities of the operating system (particularly, the
kernel) in fine detail. It provides information similar to the output of
tools like netstat, ps, top, and iostat; however, SystemTap is designed to provide more filtering and analysis options for collected information.
SystemTap in Red Hat Enterprise Linux 6.2 is updated to version 1.6, providing:
Kernel modules with a hyphen ("-") in their name, such as i2c-core are now handled properly.
process.mark now supports $$parms for reading probe parameters.
Improved and simplified operation of the SystemTap
compile-server and
client:
compile-server may cache script build results for improved performance.
compile-server and client
communicate exchange version information to adjust the communication
protocol accordingly and use the newest version of the server possible.
Removal of deprecated tools: stap-client, stap-authorize-server-cert, stap-authorize-signing-cert, stap-find-or-start-server, and stap-find-servers.
For remote execution, the --remote USER@HOST
functionality can now be specified multiple times and will
automatically build the script for distinct kernel and architecture
configurations, and run it on all named machines at once.
The staprun utility now allows multiple instances of the same script to be run at same time.
The introduction of dynamic schema generation provides a lot of
flexibility for end users to plug into Red Hat Enterprise Linux High
Availability Add-on custom resource and fence agents, and still retain
the possibility to validate their /etc/cluster.conf
configuration file against those agents. It is a strict requirement
that custom agents provide correct metadata output and that the agents
must be installed on all cluster nodes.
Support for Samba in a clustered environment is now fully supported
in Red Hat Enterprise Linux 6.2. Samba clustering relies on a clustered
file system being available and shared on all nodes. In the Red Hat
Enterprise Linux context, Samba clustering has been configured to work
with GFS2, the native shared storage file system.
Clustered Samba (more specifically CTDB) provides the ability for the
metadata to span multiple physical hosts in a cluster. CTDB will
automatically recover and repair node-specific databases in case of node
failures. It also provides high availability features like node
monitoring and failover.
The corosync-cpgtool now specifies both interfaces in a dual ring configuration. This feature is a Technology Preview.
As a consequence of converting the /etc/cluster.conf configuration file to be used by pacemaker, rgmanager must be disabled. The risk of not doing this is high; after a successful conversion, it would be possible to start rgmanager and pacemaker on the same host, managing the same resources.
Consequently, Red Hat Enterprise Linux 6.2 includes a feature (as a
Technology Preview) that forces the following requirements:
rgmanager must refuse to start if it sees the <rm disabled="1"> flag in /etc/cluster.conf.
rgmanager must stop any resources and exit if the <rm disabled="1"> flag appears in /etc/cluster.conf during a reconfiguration.
Chapter 14. High Availability
Usage of XFS in conjunction with Red Hat Enterprise Linux 6.2 High
Availability Add On as a file system resource is now fully supported.
Applications running inside VMWare based guests can now be configured
for high availability. This also includes full support for the use of
GFS2 shared storage file system in the environment. A new SOAP-based
fence agent has been added that has the ability to fence guests when
necessary.
Luci, the web-based administrative UI for configuring clusters has been updated to include the following:
IP multicasting has been the only supported option for a cluster
transport. IP multicasting is inherently complex to configure and often
requires re-configuration of network switches. UDP-unicast in contrast
offers a simpler approach to cluster configuration and is an established
protocol for cluster communication. UDP-unicast, initially introduced
as a Technology Preview, is now fully supported.
Watchdog is a general timer service available in Linux that can be
used to periodically monitor system resources. Fence agents have now
been integrated with watchdog such that the watchdog service can reboot a
node after it has been fenced using fence_scsi. This eliminates the need for manual intervention to reboot the node after it has been fenced using fence_scsi.
Chapter 15. Virtualization
- Virtual CPU timeslice sharing
Virtual CPU timeslice sharing is a performance enhancing feature at
the Linux scheduler level, where a spinning virtual CPU can hand the
remainder of its timeslice to another virtual CPU before yielding the
CPU. This feature addresses an inherent lock holder preemption issue
that exists in SMP systems, that can affect performance in virtual CPUs.
This feature provides a stable performance in multi-processor guests.
This feature is supported on both Intel and AMD processors, and is
called Pause Loop Exiting (PLE) on Intel processors, and Pause Filter on
AMD processors.
KVM network performance is a critical requirement for Virtualization
and cloud based products and solutions. Red Hat Enterprise Linux 6.2
provides a number of network performance optimizations to improve the
KVM network para-virtualized driver performance in various setups.
- Improved small message KVM performance
Red Hat Enterprise Linux 6.2 improves the KVM small message
performance to satisfy a variety of networking workloads that generate
small messages (< 4K).
- Wire speed requirement in KVM network drivers
Virtualization and cloud products that run networking work loads
need to run wire speeds. Up until Red Hat Enterprise Linux 6.1, the only
way to reach wire speed on a 10 GB Ethernet NIC with a lower CPU
utilization was to use PCI device assignment (passthrough), which limits
other features like memory overcommit and guest migration
The macvtap/vhost
zero-copy capabilities allows the user to use those features when high
performance is required. This feature improves performance for any Red
Hat Enterprise Linux 6.x guest in the VEPA use case. This feature is
introduced as a Technology Preview.
- UDP checksum optimization for KVM network drivers
UDP checksum optimization eliminates the need for the guest to
validate the checksum if it has been validated by host NICs. This
feature speeds up UDP on external to guest on 10 GB Ethernet cards
with Red Hat Enterprise Linux 6.2 guests and hosts. The UDP checksum
optimization is implemented in the virtio-net driver.
- Improved I/O path performance when host slower than guest
The Red Hat Enterprise Linux 6.2 KVM network driver has improved
I/O path performance, with reduced virtual machine exits and interrupts,
that results in faster data delivery. This also improvement enables you
to run a faster guest on a slower host, without incurring any
performance penalties. This enhancement is achieved by an enhanced virtio ring structure, and event index support in virtio and vhost-net.
- System monitoring via SNMP
This feature provides KVM support for stable technology that is
already used in data center with bare metal systems. SNMP is the
standard for monitoring and is extremely well understood as well as
computationally efficient. System monitoring via SNMP in Red Hat
Enterprise Linux 6.2 allows the KVM hosts to send SNMP traps on events
so that hypervisor events can be communicated to the user via standard
SNMP protocol. This feature is provided through the addition of a new
package: libvirt-snmp. This feature is introduced as a Technology Preview.
- Improved guest debugging capabilities
Users who virtualize their data centers need a way of debugging
when a guest OS hangs up and a crash dump has to be initiated. There are
two methods heavily used with physical systems:
While these capabilities are provided directly with the KVM console, a number of users use KVM through the libvirt API and virsh,
where these two features were missing. Red Hat Enterprise Linux 6.2
improves guest debugging capabilities across the KVM stack, thus
allowing a user to trigger NMIs in guests and send SysRq key sequences
to guests.
- Improve virtual machine boot up access
Users who virtualize their data centers need to track the guest
boot up process and display the entire BIOS and kernel boot up message
from the start. The absence of this feature prevents users from an
interactive use of the virsh console, prior to boot up. A new package, sgabios, has been be added to Red Hat Enterprise Linux 6.2, to provide this capability, along with some additions to qemu-kvm.
- Live Snapshots
Red Hat Enterprise Linux 6.2 introduces the Live Snapshot feature
as a Technology Preview. The live snapshots feature provides automatic
backup of virtual machine images on the hard drive, and provides a per
drive snapshot of the virtual disks transparently, using external qcow2
images. Multi-disk live snapshot creation helps with maintaining data
integrity by pausing qemu prior to taking as many snapshots as there are
disks. Thus, a multi-disk snapshot will have all disks containing data
from the same point in time.
It is important to know that there is a limitation with file system
consistency. However, the re-use of the snapshot image is
crash-consistent. A user would have to run a file system check (fsck) or replay journal entries, which is similar to booting after pulling the power cord.
- Multi-processor (NUMA) Tuning Improvements
Red Hat Enterprise Linux 6.2 adds tuning improvements to the libvirt
API stack, resulting in improved out-of-the-box performance when
performing SPECvirt measurements. Red Hat Enterprise Linux 6.2 is now
able to pin the memory associated with a NUMA node when a virtual
machine is created.
- USB enhancements
The USB 2.0 emulation has been implemented for qemu-kvm. This is available for QEMU directly only. Libvirt support is planned for the next release.
Remote Wakeup support has been added for the USB host controller.
Together with the cooperation of the guest OS it allows to stop the
frequent 1000hz polling mode and put the device into sleep. It
dramatically improves the power utilization and the CPU consumption of
virtual machines with a USB mouse emulation (or a tablet) — one of the
common devices that every virtual machine has.
- Memory ballooning
Memory ballooning is now supported by Red Hat Enterprise Linux 6 paravirtualized Xen guests.
- Domain memory limit
Memory limit for x86_64 domU PV guests has been increased to 128 GB: CONFIG_XEN_MAX_DOMAIN_MEMORY=128.
- Time accounting
The xen_sched_clock implementation (which returns the number of unstolen nanoseconds) has been replaced by the xen_clocksource_read implementation.
The Red Hat Enterprise Linux Virtualization Guide has been divided into several specific guides:
The package spice-protocol has been upgraded to version 0.8.1, providing the following new features:
Support for volume change
Support for async guest I/O writes and interrupts
Support for suspend (S3) related guest I/O writes
Support for interrupt indicating a guest bug
Linux containers provide a flexible approach to application runtime
containment on bare-metal systems without the need to fully virtualize
the workload. Red Hat Enterprise Linux 6.2 provides application level
containers to separate and control the application resource usage
policies via cgroup and namespaces. This release introduces basic
management of container life-cycle by allowing creation, editing and
deletion of containers via the libvirt API and the virt-manager GUI. Linux Containers are a Technology Preview.
In order to allow side-by-side installs of the rhev-hypervisor package, configure Yum to make rhev-hypervisor an installonly package by editing the /etc/yum.conf file and adding the installonlypkgs option:
[main]
...
installonlypkgs=rhev-hypervisor
This option needs to also include the default list of installonly packages which can be found in the yum.conf man page (man yum.conf 5) in the installonlypkgs option section.
The X server shipped in Red Hat Enterprise Linux 6.2 has been updated
to the upstream X.org 1.10 X server and the upstream Mesa 7.11 releases.
nThe X server had internal structure changes that required updating all
video and input drivers. In addition, the kernel graphics support has
been updated to include new hardware support and bug fixes.
Improved support for ATI/AMD GPU series HD2xxx, HD4xxx, HD5xxx,
FirePro. Support added for new HD6xxx series, new model in the FirePro
series and new mobile GPU HD6xxxM series.
Support has been added for Intel's next generation class of chipsets.
2D/Xv acceleration is now supported on GeForce GT2xx (and Quadro equivalents). Suspend/resume support has been improved.
RandR-enabled drivers (intel, nouveau, radeon) now confine the cursor
to the visible area of the screen in asymmetric multihead
configurations.
The Composite extension is now functional when Xinerama is used to span a single desktop across multiple GPUs.
X server configuration may now be managed with configuration file snippets under /etc/X11/xorg.conf.d/ in addition to /etc/X11/xorg.conf
itself. X.org input device configuration in these snippets applies when
the device becomes available to the X server at runtime.
Chapter 17. General Updates
Matahari in Red Hat Enterprise Linux 6.2 is fully supported only for
x86 and AMD64 architectures. Builds for other architectures are
considered a Technology Preview.
Red Hat Enterprise Linux 6.2 introduces ABRT 2.0. ABRT
logs details of software crashes on a local system, and provides
interfaces (both graphical and command line based) to report issues to
various issue trackers, including Red Hat support. This update provides
the following notable enhancements:
More flexible configuration with a new syntax.
Out-ouf-process plugins (plugins run in separate processes and
communicate via inter-process communication with other processes).
Advantages of such a design are:
bugs in plugins do not break the main daemon,
more secure as most of the processing is now done under the normal (non-root) user,
plugins can be written in any programming language.
Reporting backend is shared across all of Red Hat's issue reporting tools:
ABRT, sealert, all users of python-meh (Anaconda, firstboot)
Because all of the tools above share the same configuration, it only has to be written once.
Red Hat Enterprise Linux 6.2 provides an optimized linear algebra
math library for Linux on System z which enables the compiler to
generate code for high profile functions, taking advantage of the latest
hardware functions.
Red Hat Enterprise Linux 6.2 improves support for Wacom devices. It
is no longer necessary to reconfigure device settings after a device has
been unplugged and plugged back in.
NetworkManager can now scan wireless networks in the background, providing a better user experience.
The gnome-system-monitor utility can now monitor systems that have more than 64 CPUs.
This appendix is a list of components and their versions in the Red Hat Enterprise Linux 6.2 release.
Table A.1. Component Versions
|
Component
|
Version
|
|---|
|
Kernel
|
2.6.32-202
|
|
QLogic qla2xxx driver
|
8.03.07.05.06.2-k
|
|
QLogic qla2xxx firmware
|
ql23xx-firmware-3.03.27-3.1
ql2100-firmware-1.19.38-3.1
ql2200-firmware-2.02.08-3.1
ql2400-firmware-5.06.01-1
ql2500-firmware-5.06.01-1
|
|
Emulex lpfc driver
|
8.3.5.45.2p
|
|
iSCSI initiator utils
|
6.2.0.872-27
|
|
DM-Multipath
|
0.4.9-43
|
|
LVM
|
2.02.87-3
|
|
X Server
|
1.10.4-3
|
| Revision History |
|---|
| Revision 1-0 | Tue Dec 6 2011 | Martin Prpič |
| Release of the Red Hat Enterprise Linux 6.2 Release Notes |
|