Visualizing the flow

Multicore systems have led to processes and threads executing concurrently on different processors. This is useful for gaining higher throughput and thus performance, but also causes synchronization headaches with shared writable data. So, for example, on a hardware platform with, say, four processor cores, we can expect processes (and threads) to execute in parallel on them. This is nothing new; is there a way, though, to actually see which processes or threads are executing on which CPU core – that is, a way to visualize a processor timeline? It turns out there are indeed a few ways to do so. In the following sections, we will look at one interesting way with perf, followed later by others (with LTTng, Trace Compass, and Ftrace).