Real-Time Linux

Real-Time Linux, a set of patches to improve scheduling consistency and available in SUSE Linux Enterprise Real Time and RedHat Enterprise MRG.

Linux latency in microseconds at 10,000 packets-per-second one-way.

Y-axis is latency in microseconds, X-axis is time in seconds. Chart records test of 10,000 packets-per-second send out and received, a total of 20,000 datagrams-per-second. The left hand side shows Linux 2.6.36 with normal scheduling (SCHED_OTHER) with a tight grouping around 200μs; the right hand side shows Linux 2.6.26 with real-time scheduling (SCHED_FIFO) with tighter grouping at 200μs but larger spread of outliers.

Linux latency in microseconds at 20,000 packets-per-second one-way.

Normal scheduler shows a tight grouping at 250μs with minor spread of outliers; real time scheduling shows grouping at a better latency of 200μs but higher spread of outliers.

Linux latency in microseconds at 30,000 packets-per-second one-way.

Normal scheduler shows grouping at 250μs with spread from 200μs-1ms; real time scheduling shows spread of grouping 200-250μs with outliers to 1ms.

Linux latency in microseconds at 40,000 packets-per-second one-way.

Normal scheduler shows grouping 200-600μs with outliers spread to 2ms; real time scheduling shows grouping 250-300μs with outliers spread to 1.5ms with a strange gap from 1.0-1.3ms.