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The kernel column #94 by Jon Masters

Nov 22, 2010, 17:33 (0 Talkback[s])
(Other stories by Jon Masters)

[ Thanks to Linux User & Developer magazine for this link. ]

"This month saw the final release of kernel 2.6.36, and the closing of the following 'merge window' for new features to be merged into what will become the 2.6.37 kernel (more details about the latter in a moment). The 2.6.36 kernel features concurrency-managed workqueues, preliminary support for the fanotify mechanism discussed here in the past, final merging of the AppArmor security system used by some distributions for many years, and support for a new architecture, among many dozens of other significant improvements. The new kernel received patches from over 1,100 engineers for a total of nearly 11,000 changesets (collections of related changes to various kernel files) overall.

"Concurrency-managed workqueues

"Workqueues are one of the not particularly sexy but necessary pieces of kernel infrastructure code that provide a means for developers to schedule execution of some function at a more convenient time. They run that function within a special kernel thread – visible using the 'top' and 'ps' commands – in what is known as 'process' context (Linux has historically differentiated more between the limited 'interrupt' and 'process' context for what features code could use at the time, but this is changing slowly with the mixture of newer threaded interrupt support). Over the years, workqueue use has become so profuse within drivers and other kernel code that a typical system may have many hundreds – or even thousands – of kernel threads dedicated to them, often competing at unfortunate times for the CPU, and at other times doing nothing other than existing and clogging up lists of running processes."

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