On The Move

Kernel Log Penguin Numerous long awaited changes adopted in 2.6.29 should improve the reliability of system suspend mode. Torvalds explicitly stressed these changes on releasing the third pre-release version of 2.6.29. Suspend and resume have previously worked on many systems, but, due to interrupt timing problems, especially with shared interrupts, had not always been reliable. Problems with the new suspend code were, however, uncovered during development, necessitating many further changes. More such changes can be expected in 2.6.30.

Changes to the p4-clockmod driver, which removed the Cpufreq driver's Sysfs interface, were initially adopted, but then withdrawn. As with previous kernel versions, in 2.6.29 it will remain possible to manually slow down the CPU using throttling â though as previously reported, this is rarely worthwhile. The withdrawal of these changes is, however, an interim measure only, to allow the development team to correct certain bugs in ACPI subsystem throttle support in order to ensure the reliability of protection against CPU overheating. The plan is that the patch will then be reintroduced, with release pencilled in for this September.

The i8k driver for Dell laptops has been extended to add support for the Vostro and Precision series and includes a new dell-laptop driver, which supports brightness control and querying of the WLAN switch via Dcdbas (Dell Systems Management Base Driver).

Source code control system as an information source
Many of the links in this article link to the relevant commit in the web front end for the Linux source code (which is maintained by Linus Torvalds using Git), where much additional information on the changes in question can be found. In particular, the comments in the middle of the commit web page served by the Git front end are frequently an extremely useful source of further information, as patch authors usually give a broad explanation of the background to the change and what it is intended to achieve. The comments also sometimes include links to more detailed information on other websites and the results of speed tests. The bottom of the Git front end includes a list of the files changed by the patch. Clicking on the 'diff' link following the file name shows how the patch associated with the commit has changed the relevant file. Users wishing to scrutinise the complete patch in its raw state can do so by clicking on the commitdiff link at the top of the page. The patches are thus â even for those with no programming knowledge â frequently a useful source of information, since they also contain changes to the documentation and comments on the code.

Fastboot

Following on from his "Fastboot" enhancements introduced in 2.6.28, which accelerate the kernel initialisation phase and thereby system start-up, Arjen van de Ven has generated further improvements in this area for 2.6.29. These now allow the kernel to initialise some mutually-independent subsystems asynchronously, i.e. to start initialisation of one subsystem whilst code from another subsystem is still, for example, waiting for a response from the hardware it deals with. This kind of wait is especially common when initialising the Libata and SCSI subsystems, which at some points wait for tenths of a second or longer for a response from the drive, when querying and setting up media.

This trick allows the boot phase between starting the kernel and transferring to userspace (/sbin/init) to be measurably and tangibly faster â the magnitude of the benefit is strongly system-dependent. Due to some problems, however, parallel initialisation will be largely deactivated in 2.6.29 unless the fastboot code is explicitly activated using the "fastboot" kernel parameter. Van de Ven is planning to take a second shot at the problem in 2.6.30 to allow more users to benefit from these changes. More details on how fastboot works can be found in an article on LWN.net.

Next: New drivers for audio, FireWire, USB and video hardware, staging changes

Â« previous 1 2 3 4 5 6 next Â»

Print Version | Permalink: http://h-online.com/-746553