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New Ways to Find Latency in Linux Using Tracing

Ftrace is the official tracer of the Linux kernel. It originated from the real-time patch (now known as PREEMPT_RT), as developing an operating system for real-time use requires deep insight and transparency of the happenings of the kernel. Not only was tracing useful for debugging, but it was critical for finding areas in the kernel that was causing unbounded latency. It's no wonder why the ftrace infrastructure has a lot of tooling for seeking out latency. Ftrace was introduced into mainline Linux in 2008, and several talks have been done on how to utilize its tracing features. But a lot has happened in the past few years that makes the tooling for finding latency much simpler. Other talks at P99 discuss the new ftrace tracers "osnoise" and "timerlat", but this talk focuses more on the new flexible and dynamic aspects of ftrace that facilitates finding latency issues which are more specific to your needs. Some of this work may still be in a proof of concept stage, but this talk gives you the advantage of knowing what tools will be available to you in the coming year.