Add "Making Clippy blazingly fast by 2024"

posts/inside-rust/2023-08-21-clippy-perf-project.md

@@ -0,0 +1,79 @@
+---
+layout: post
+title: "Making Clippy blazingly fast by 2024"
+author: Alejandra González
+team: the Clippy team <https://www.rust-lang.org/governance/teams/dev-tools#Clippy%20team>
+description: This is the start of a series of posts talking about optimizations done on the Clippy codebase. 
+---
+
+Clippy's codebase is designed to be beginner-friendly so new contributors can come and learn,
+not optimized for performance. It was never a priority to make Clippy fast because *it never needed
+to be.* But time passed and more lints were added, now we have [over 650 lints][lint_list], each one of them adding a bit of performance overhead. In big projects this can take over a minute to check all those lints, so the Clippy team have decided to do something about it.
+
+> <span class="note"><svg class="note-icon" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg> Full disclosure</span>
+>
+> While some members are being sponsored by Embark Studios to continue / improve these efforts, these optimizations are and will be always free and open source. No brands attached.
+
+The final goal of this project (and series of posts) is being able to run Clippy
+quickly after save, making it a sort of IDE-companion, instead of a
+totally external tool run in the CLI. Consuming less time / power on
+CI checks would be a secondary goal, achieved collaterally
+(but very much appreciated!).
+
+## Careful analysis of the situation
+
+Before opening your IDE, you must think "what is the biggest
+bottleneck in my codebase's performance?". Do not start optimizing your
+big functions that are only run once, optimize those small functions
+that, even being small, clog your code. With some profiling we
+discovered that the function [`clippy_utils::is_from_proc_macro`][from_proc_macro]
+takes up *25%* of the runtime, even just being used in 32
+occasions. This function will be our primary target for this period.
+
+## Preparing strategies
+
+The team held [this Zulip thread](zulip_thread) talking about the whole situation.
+
+From that thread, a lot of optimization opportunities came up. It revived [this issue], and
+[this PR][this_pr] not long after (maybe because of the thread, maybe not) 🎉, resulting in a significant performance boost.
+
+## Crafting a cartography of our problem
+
+So, we decided to focus more on this section of the Clippy project. By the end of 2024 the following goals should have accomplished the following goals:
+
+- `is_from_proc_macro` use should be O(log n) time complexity instead of the current O(n).
+- `rustc` and by proxy, Clippy, should not process allowed / disabled by default lints.
+- Tools should be made to automatically benchmark every week or so the Clippy repo to check for regressions (we don't need per-commit benchmarking)
+
+These 3 objectives are the goal for this period, the next period
+an update will be released with how much performance increased from the
+last update and what are our next objectives.
+
+## A final note
+
+The <span class="perf-project"><b>Performance project</b></span> is big, it
+will (hopefully) be done by 2024 maybe it's delayed. I'll be writing
+updates on this topic about every 1 or 2 months, so you (the
+community) knows how it's going. Let's hope Clippy
+is **blazingly fast** by 2024 🦀.
+
+[lint_list]: https://rust-lang.github.io/rust-clippy/
+[from_proc_macro]: https://doc.rust-lang.org/beta/nightly-rustc/clippy_utils/fn.is_from_proc_macro.html
+[zulip_thread]: https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/Clippy's.20performance/near/366555916
+[this_pr]: https://github.com/rust-lang/rust/pull/114026
+[this_issue]: https://github.com/rust-lang/rust/issues/106983
+
+<style>
+    .note {
+        color: #2169DF;
+    }
+
+    .note-icon {
+        fill: #2169DF;
+        top: 2px;
+    }
+
+    .perf-project {
+        text-shadow: 0px 2px 0px #ffc832;
+    }
+</style>