The mozperftest project was created with the intention to replace all existing performance testing frameworks that exist in the mozilla central source tree with a single one, and make performance tests a standardized, first-class citizen, alongside mochitests and xpcshell tests.

We want to give the ability to any developer to write performance tests in their component, both locally and in the CI, exactly like how they would do with xpcshell tests and mochitests.

Historically, we have Talos, that provided a lot of different tests, from micro-benchmarks to page load tests. From there we had Raptor, that was a fork of Talos, focusing on page loads only. Then mach browsertime was added, which was a wrapper around the browsertime tool.

All those frameworks besides mach browsertime were mainly focusing on working well in the CI, and were hard to use locally. mach browsertime worked locally but not on all platforms and was specific to the browsertime framework.

mozperftest currently provides the mach perftest command, that will scan for all tests that are declared in ini files such as and registered under PERFTESTS_MANIFESTS in files such as

If you launch ./mach perftest without any parameters, you will get a full list of available tests, and you can pick and run one. Adding –push-to-try will run it on try.

The framework loads perf tests and read its metadata, that can be declared within the test. We have a parser that is currently able to recognize and load xpcshell tests and browsertime tests, and a runner for each one of those.

But the framework can be extended to support more formats. We would like to add support for jsshell and any other format we have in m-c.

A performance test is a script that perftest runs, and that returns metrics we can use. Right now we consume those metrics directly in the console, and also in perfherder, but other formats could be added. For instance, there’s a new influxdb output that has been added, to push the data in an influxdb time series database.

What is important is to make sure performance tests belong to the component it’s testing in the source tree. We’ve learned with Talos that grouping all performance tests in a single place is problematic because there’s no sense of ownership from developers once it’s added there. It becomes the perf team problem. If the tests stay in each component alongside mochitests and xpcshell tests, the component maintainers will own and maintain it.

Next steps

We want to rewrite all Talos and Raptor tests into perftest. For Raptor, we need to have the ability to use proxy records, which is a work in progress. From there, running a raptor test will be a simple, one liner browsertime script.

For Talos, we’ll need to refactor the existing micro-benchmarks into xpchsell tests, and if that does not suffice, create a new runner.

For JS benchmarks, once the jsshell runner is added into perftest, it will be straightforward.