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Fast response times is not always just a perk, but also can be a hard requirement. Over the years, Linux response times has improved tremendously. For a hard realtime response, applying the PREEMPT_RT patch can remove unbounded latencies caused by priority inversion and also improve responses by removing most places that disable preemption in the kernel.
But even with the best Real-Time Operating System (RTOS), the system is a slave to the hardware. If the hardware has System Management Interrupts (SMI), the system can halt at anytime, and the OS can do nothing about it. Finding these can be tricky if the hardware does not give you any clue to what it may do.
This talk will discuss ways to discover hardware latencies such as SMIs,using the PREEMPT_RT patch along with the hwlat_detector that comes with it, as well as using ftrace and kernelshark.
