Document and improve (a lot) lintcheck --perf #14194
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Introducing a new chapter to the book, known as "Benchmarking Clippy". It explains the benchmarking capabilities of lintcheck --perf and gives a concrete example on how benchmark and compare a PR with master
rustbot
added
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- Now lintcheck perf deletes target directory after benchmarking, benchmarking with a cache isn't very useful or telling of any precise outcome. - Support for benchmarking several times without having to do a cargo clean. Now we can benchmark a PR and master (or a single change in the same commit) without having to move the perf.data files into an external directory. - Compress perf.data to allow for allowing multiple stacks and occupy much less space
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Maybe we should integrate this into the CI as well. If this is costly (I haven't had a chance to try it yet), we may even be able to watch the comments and react to certain commands, as we would do with a bot. |
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r? @Alexendoo I won't get to review this any time soon. And I think, Alex is the better reviewer for this anyway. |
BD103
reviewed
Feb 24, 2025
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| The first `perf.data` will not have any numbers appended, but any subsequent | ||
| benchmark will be written to `perf.data.number` with a number growing for 0. | ||
| All benchmarks are compressed so that you can |
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Looks like the end of this sentence is missing! :)
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Alexendoo
reviewed
Feb 26, 2025
| cmd.args(&[ | ||
| "record", | ||
| "-e", | ||
| "instructions", // Only count instructions | ||
| "-g", // Enable call-graph, useful for flamegraphs and produces richer reports | ||
| "--quiet", // Do not tamper with lintcheck's normal output | ||
| "--compression-level=22", |
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Does this not slow down the capture? zstd 22 is pretty slow
| cmd.args(&[ | ||
| "record", | ||
| "-e", | ||
| "instructions", // Only count instructions | ||
| "-g", // Enable call-graph, useful for flamegraphs and produces richer reports | ||
| "--quiet", // Do not tamper with lintcheck's normal output | ||
| "--compression-level=22", | ||
| "--freq=97", // Slow down program to capture all events |
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This reduces the sampling frequency considerably meaning fewer captured events
There is no way to capture all the events with perf record as it is a sampling profiler
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In #14116 we added a benchmarking option for Lintcheck, this commit adds a new chapter to the book AND improves that option into a more usable state.
It's recommended to review one commit at a time.
Document how to benchmark with lintcheck --perf
Several improvements on lintcheck perf (desc.)
Now lintcheck perf deletes target directory after benchmarking,
benchmarking with a cache isn't very useful or telling of any
precise outcome.
Support for benchmarking several times without having to do
a cargo clean.
Compress perf.data
changelog: none