Add basic performance check#151
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This property of a test is very stable, however only a very rough estimate of the resource needs. The limits in the tests are chosen in such a way that moderate growth still won't make tests fail. Still having a warning on substantial changes might prevent some mistakes, and making the metrics that bazel collects anyway available to tests is cheap.
These metrics are less stable, especially when using persistent workers to build the test fixtures; nevertheless, they are closer to the actual build evaluation. Due to their unstable nature, limits are chosen generously, just making sure huge performance changes are detected.
After a build run bazel info used-heap-size-after-gc to ask bazel of the heap size still in use after the build. This is a good proxy for the memory of the final dependency graph. This metrics should be valid even though we use bazel persistent workers, as a change of sample project completely invalidates the project-specific parts of the old project and only valid graph parts are kept between builds.
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As we frequently extend our aspect to obtain more information, we should have same basic sanity-checks warning us if we accidentally increase the build size too much. To do so, we use metrics that bazel collects anyway and focus on stable ones.