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The Linux distillery A bright open source future
The Linux distillery A bright open source future | A bright open source future |
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| by David M Williams | |
| Thursday, 10 April 2008 | |
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Page 1 of 3
2.6.24 including new features like CPU group scheduling – which grouped related processes and allocated processor time to these rather than concentrating on individual tasks irrespective of how many tasks and overall CPU time were being spent on the same user. Another notable inclusion was memory fragmentation avoidance which was particularly pertinent given the legendary stories of Linux boxes running days or months without rebooting. Typically, this causes memory fragmentation which makes certain tasks more difficult, specifically allocating memory larger than the native page size which is 4KB on x86 architectures. Developers worked on anti-fragmentation techniques for three years and these all merged with 2.6.24. Linux kernel 2.6.25 can be expected out sometime this month. A prepatch release candidate came out on April 1st, although it was no joke. We can expect at most one more prepatch before the final 2.6.25 release. One expected feature is extra work on group scheduling. Some background information: being a multitasking operating sysem Linux divides processor time up so each task runs for a small period of time before being suspended and another task having an opportunity to run. This gives the illusion that many different tasks are all actually running at the very same time and is especially important on a multi-user system. Linux employs several tricks to determine how long a task should be permitted to run before being suspended and to determine which task to run next. Typically these are based on whether the task is waiting for an input device to respond – like a disk or keyboard, whether the task is computationally intense and chewing up the CPU, how it has behaved in the past and so on. These techniques proved reliable but until 2.6.24 it was still possible for an individual user to starve other users of CPU time. 2.6.25 now bolsters the group scheduling developments so that real time processes are properly handled. These are a special type of process which absolutely must run regularly and reliably and which handle things like life-support systems. Real time tasks now have definite scheduling guarantees and optimum behaviour. Another interesting development – although one which is pretty much just academic for most of the world – is that Linux can now support up to 65,536 processors. I’d certainly like to see a suitably-equipped computer! Some more practical, and definitely immediately useful, items are SMACK and Latencytop. You will no doubt find these of interest. Please read on! CONTINUED
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