| Description: | The tuned packages contain a daemon that tunes system settings dynamically. It does so by monitoring the usage of several system components periodically.
This update fixes the following bugs:
Red Hat Enterprise Linux 6.1 and later enters processor power-saving states more aggressively. This could result in a small performance penalty on certain workloads. With this update, the pmqos-static.py daemon has been added to the tuned packages, which allows to set the requested latency using the kernel Power Management QoS interface. It is run when the "latency-performance" profile is activated and it sets cpu_dma_latency=0, which keeps the CPU in C0 state, thus making the system as responsive as possible. (BZ#714180)
When the ELEVATOR_TUNE_DEVS option was set to a disk device in the /etc/sysconfig/ktune file instead of providing a disk scheduler control file, the scheduler setting was not written to a disk scheduler control file but directly into the disk device file. Consequently, contents of the disk could become corrupted. With this update, the value of ELEVATOR_TUNE_DEVS is checked and only the disk scheduler control file is allowed for writing. As a result, an invalid value of ELEVATOR_TUNE_DEVS is detected in the described scenario so that the disk contents damage can be prevented. (BZ#784308)
When the tuned daemon run with the "enterprise-storage" profile enabled and a non-root, non-boot disk partition from a device with write-back cache was mounted, tuned remounted the partition with the "nobarriers" option. If a power failure occurred at that time, the file system could become corrupted. With this update, tuned can detect usage of write-back cache on devices communicating with kernel via SCSI. In these cases, "nobarriers" is now disabled, thus preventing this bug in the described scenario. (BZ#801561)
Previously, when the tuned service was started, the tuned PID file was created with world-writable permissions. This bug has been fixed and the /var/run/tuned/tuned.pid file is now created with correct permissions as expected. (BZ#845336)
On a machine with hot-plug disk devices with the "enterprise-storage" profile activated, a new disk device could be added into the system, or the disk could be removed and inserted back. In such a scenario, the scheduler and read-ahead settings from the profile were not applied on the newly-added disks. With this update, a new udev rule has been added, which restarts the ktune daemon whenever a new disk device is added, thus fixing this bug. (BZ#847445)
The transparent hugepage kernel thread could interfere with latency-sensitive applications. To lower the latency, the transparent hugepages are now disabled in the latency-performance tuned profile. (BZ#887355)
Previously, non-root, non-boot partitions were re-mounted using the "nobarrier" option to improve performance. On virtual guests, this could lead to data corruption if power supply was suddenly interrupted, because there was usually a host cache in transfer. This bug has been fixed and the virtual-guest profile no longer re-mounts partitions using "nobarrier". (BZ#886956)
Users of tuned are advised to upgrade to these updated packages, which fix these bugs.
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