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LinuxDevices.com: Linux Scheduler Latency

Mar 22, 2002, 01:00 (6 Talkback[s])
(Other stories by Clark Williams)

"Since I'm primarily interested in embedded Linux and since most embedded Linux systems are uniprocessor systems, my testing focused exclusively on uniprocessors systems. I tested both patches on a 2.4.17 kernel under heavy load and while both patches significantly reduced kernel latency, the testing shows that the low-latency patches yielded the best reduction of Linux scheduler latency. The low-latency patches had a maximum recorded latency of 1.3 milliseconds, while the preemption patches had a maximum latency of 45.2ms.

"A 2.4.17 kernel patched with a combination of both preemption and low-latency patches yielded a maximum scheduler latency of 1.2 milliseconds, a slight improvement over the low-latency kernel. However, running the low-latency patched kernel for greater than twelve hours showed that there are still problem cases lurking, with a maximum latency value of 215.2ms recorded. Running the combined patch kernel for more than twelve hours showed a maximum latency value of 1.5ms. This data seems to indicate that the best solution for reducing Linux scheduler latency is to combine both sets of patches..."

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