inferno 0.11.19

Rust port of the FlameGraph performance profiling tool suite
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Inferno is a port of parts of the flamegraph toolkit to Rust, with the aim of improving the performance of the original flamegraph tools. The primary focus is on speeding up the stackcollapse-* tools that process output from various profiling tools into the "folded" format expected by the flamegraph plotting tool. So far, the focus has been on parsing profiling results from perf and DTrace. At the time of writing, inferno-collapse-perf is ~20x faster than and inferno-collapse-dtrace is ~20x faster than (see

It is developed in part through live coding sessions, which you can find on YouTube.

Using Inferno

As a library

Inferno provides a library interface through the inferno crate. This will let you collapse stacks and produce flame graphs without going through the command line, and is intended for integration with external Rust tools like cargo-flamegraph.

As a binary

First of all, you may want to look into cargo flamegraph, which deals with much of the infrastructure for you!

If you want to use Inferno directly, then build your application in release mode and with debug symbols, and then run a profiler to gather profiling data. Once you have the data, pass it through the appropriate Inferno "collapser". Depending on your platform, this will look something like

$ # Linux
# perf record --call-graph dwarf target/release/mybin
$ perf script | inferno-collapse-perf > stacks.folded


$ # macOS
$ target/release/mybin &
$ pid=$!
# dtrace -x ustackframes=100 -n "profile-97 /pid == $pid/ { @[ustack()] = count(); } tick-60s { exit(0); }"  -o out.user_stacks
$ cat out.user_stacks | inferno-collapse-dtrace > stacks.folded

You can also use inferno-collapse-guess which should work on both perf and DTrace samples. In the end, you'll end up with a "folded stack" file. You can pass that file to inferno-flamegraph to generate a flame graph SVG:

$ cat stacks.folded | inferno-flamegraph > flamegraph.svg

You'll end up with an image like this:

colorized flamegraph output

Obtaining profiling data

To profile your application, you'll need to have a "profiler" installed. This will likely be perf or [bpftrace] on Linux, and [DTrace] on macOS. There are some great instructions on how to get started with these tools on Brendan Gregg's [CPU Flame Graphs page].

[profiler]: [perf]: [bpftrace]: [DTrace]: [CPU Flame Graphs page]:

On Linux, you may need to tweak a kernel config such as

$ echo 0 | sudo tee /proc/sys/kernel/perf_event_paranoid

to get profiling to work.


Comparison to the Perl implementation

To run Inferno's performance comparison, run ./ It requires hyperfine, and you must make sure you also check out Inferno's submodules. In general, Inferno's perf and dtrace collapsers are ~20x faster than stackcollapse-*, and the sample collapser is ~10x faster.


Inferno includes criterion benchmarks in benches/. Criterion saves its results in target/criterion/, and uses that to recognize changes in performance, which should make it easy to detect performance regressions while developing bugfixes and improvements.

You can run the benchmarks with cargo bench. Some results (YMMV):

My desktop computer (AMD Ryzen 5 2600X) gets (/N means N cores):

collapse/dtrace/1       time:   [8.2767 ms 8.2817 ms 8.2878 ms]
                        thrpt:  [159.08 MiB/s 159.20 MiB/s 159.29 MiB/s]
collapse/dtrace/12      time:   [3.8631 ms 3.8819 ms 3.9019 ms]
                        thrpt:  [337.89 MiB/s 339.63 MiB/s 341.28 MiB/s]

collapse/perf/1         time:   [16.386 ms 16.401 ms 16.416 ms]
                        thrpt:  [182.37 MiB/s 182.53 MiB/s 182.70 MiB/s]
collapse/perf/12        time:   [4.8056 ms 4.8254 ms 4.8460 ms]
                        thrpt:  [617.78 MiB/s 620.41 MiB/s 622.97 MiB/s]

collapse/sample         time:   [8.9132 ms 8.9196 ms 8.9264 ms]
                        thrpt:  [155.49 MiB/s 155.61 MiB/s 155.72 MiB/s]

flamegraph              time:   [16.071 ms 16.118 ms 16.215 ms]
                        thrpt:  [38.022 MiB/s 38.250 MiB/s 38.363 MiB/s]

My laptop (Intel Core i7-8650U) gets:

collapse/dtrace/1       time:   [8.3612 ms 8.3839 ms 8.4114 ms]
                        thrpt:  [156.74 MiB/s 157.25 MiB/s 157.68 MiB/s]
collapse/dtrace/8       time:   [3.4623 ms 3.4826 ms 3.5014 ms]
                        thrpt:  [376.54 MiB/s 378.58 MiB/s 380.79 MiB/s]

collapse/perf/1         time:   [15.723 ms 15.756 ms 15.798 ms]
                        thrpt:  [189.51 MiB/s 190.01 MiB/s 190.41 MiB/s]
collapse/perf/8         time:   [6.1391 ms 6.1554 ms 6.1715 ms]
                        thrpt:  [485.09 MiB/s 486.36 MiB/s 487.65 MiB/s]

collapse/sample         time:   [9.3194 ms 9.3429 ms 9.3719 ms]
                        thrpt:  [148.10 MiB/s 148.56 MiB/s 148.94 MiB/s]

flamegraph              time:   [16.490 ms 16.503 ms 16.518 ms]
                        thrpt:  [37.324 MiB/s 37.358 MiB/s 37.388 MiB/s]


Inferno is a port of @brendangregg's awesome original FlameGraph project, written in Perl, and owes its existence and pretty much of all of its functionality entirely to that project. Like FlameGraph, Inferno is licensed under the CDDL 1.0 to avoid any licensing issues. Specifically, the CDDL 1.0 grants

a world-wide, royalty-free, non-exclusive license under intellectual property rights (other than patent or trademark) Licensable by Initial Developer, to use, reproduce, modify, display, perform, sublicense and distribute the Original Software (or portions thereof), with or without Modifications, and/or as part of a Larger Work; and under Patent Claims infringed by the making, using or selling of Original Software, to make, have made, use, practice, sell, and offer for sale, and/or otherwise dispose of the Original Software (or portions thereof).

as long as the source is made available along with the license (3.1), both of which are true since you're reading this file!