hotspot VS cargo-flamegraph

perf with Hotspot 👌

If you’re able to use perf on Linux, I would recommend hotspot for visualizing the results.

I can recommend you using the https://github.com/KDAB/hotspot/ tool whenever you want to study performance.

Every Linux C/C++/Rust developer should know about https://github.com/KDAB/hotspot. It's convenient and fast. I use it for Rust all the time, and it provides all of these features on the back of regular old `perf`.

Flamegraphs alone aren't a full picture of what your application is doing, but it can give you hints as to where to look. Another tool I often use is Hotspot which can open the perf.data file and provide more options for filtering and digging into the gathered data beyond the single flamegraph.

Ignore the command, it's just a placeholder to get meaningful values. The -d flag adds basic cache events, by adding another -d you also get load and load miss events for the dTLB, iTLB and L1i cache.

But as mentioned, you can instrument any event supported by your system. Including very obscure events such as uops_executed.cycles_ge_2_uops_exec (Cycles where at least 2 uops were executed per-thread) or frontend_retired.latency_ge_2_bubbles_ge_2 (Retired instructions that are fetched after an interval where the front-end had at least 2 bubble-slots for a period of 2 cycles which was not interrupted by a back-end stall).

You can also record data using perf-record(1) and inspect them using perf-report(1) or - my personal favorite - the Hotspot tool (https://github.com/KDAB/hotspot).

Sorry for hijacking the discussion a little, but I think perf is an awesome little tool and not as widely known as it should be. IMO, when using it as a profiler (perf-record), it is vastly superior to any language-specific built-in profiler. Unfortunately some languages (such as Python or Haskell) are not a good fit for profiling using perf instrumentation as their stack frame model does not quite map to the C model.

> [...] how Perf compares to vendor tools like vTune [...] ?

Regarding the hardware events that Perf can capture on x86, it has pretty much all of them. So it should be equivalent to vTune for all practical purposes.

The big difference is in the UI -- or absence thereof. Perf is a low-level tool and its output is mostly text files. There is a curses-based TUI for perf-report (and even gtk version, but it is essentially the same as the TUI, just using GTK2 widgets), but that's about it.

By contrast, vTune comes with a heavy (electron-based?) GUI and is quite helpful in guiding beginners, with many graphs and explanations.

Of course, one can (and is expected to) complement Perf with an assortment of tools that process its output for visualization. For example, the flamegraph [1] and heat map [2] tools described in the article. But also KDAB hotspot [3] or HPerf for a vTune-style perf-report.

[1] https://github.com/brendangregg/FlameGraph

[2] https://github.com/brendangregg/HeatMap

[3] https://github.com/KDAB/hotspot

[4] https://www.poirrier.ca/hperf/

https://github.com/KDAB/hotspot might contain parsing code you could use as an example (other than perf script). It always accepts raw perf.data, and there doesn't seem to be a way to feed it the output of perf script, so it might be parsing it directly instead of calling perf script.

I'd suggest cargo flamegraph https://github.com/killercup/cargo-flamegraph

Check out cargo flamegraph.

cargo-flamegraph is a very simple and portable tool to understand where the time is spent in your application. If you want more detailed info, try this: perf record -g --call-graph=dwarf /path/to/your/application and then load it into Firefox Profiler. That's the best profiling UI available.