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What do you need to know about Perf in Linux?
Perf is a profiler tool for Linux 2.6+ based systems that abstracts away CPU hardware differences in Linux performance measurements and presents a simple commandline interface. Perf is based on the perf_events interface exported by recent versions of the Linux kernel.
What happens if there are more events than counters in PERF?
In that case, perf will report an error. See the troubleshooting section for help with this matter. If there are more events than counters, the kernel uses time multiplexing (switch frequency = HZ, generally 100 or 1000) to give each event a chance to access the monitoring hardware.
Is it possible to print large numbers in PERF?
For most people, it is hard to read large numbers. With perf stat, it is possible to print large numbers using the comma separator for thousands (US-style). For that the -B option and the correct locale for LC_NUMERIC must be set. As the above example showed, Ubuntu already sets the locale information correctly.
How is sample analysis done with perf report?
Sample analysis with perf report. Samples collected by perf record are saved into a binary file called, by default, perf.data. The perf report command reads this file and generates a concise execution profile. By default, samples are sorted by functions with the most samples first.
Which is an example of a perf profiler?
These are some examples of using the perf Linux profiler, which has also been called Performance Counters for Linux (PCL), Linux perf events (LPE), or perf_events. Like Vince Weaver, I’ll call it perf_events so that you can search on that term later.
What does perf report show on a disk?
A summary of the perf.data file was printed using perf report, which builds a tree from the stack traces, coalescing common paths, and showing percentages for each path. The perf report output shows that 2,216 events were traced (disk I/O), 32% of which from a dd command.
How to select an event in PERF record?
Selection can be: • a symbolic event name (use perf list to list all events) • a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a hexadecimal event descriptor. • a symbolic or raw PMU event followed by an optional colon and a list of event modifiers, e.g., cpu-cycles:p.