Profiling example

crates/ra_hir_ty/src/infer.rs

@@ -65,6 +65,11 @@ mod coerce;
 /// The entry point of type inference.
 pub(crate) fn infer_query(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult> {
     let _p = profile("infer_query");
+    let _cpu_profieler;
+    if ra_prof::Scope::is_active() {
+        _cpu_profieler = ra_prof::cpu_profiler();
+    }
+
     let resolver = def.resolver(db.upcast());
     let mut ctx = InferenceContext::new(db, def, resolver);
 

crates/ra_ide/src/completion.rs

@@ -106,6 +106,7 @@ pub(crate) fn completions(
     config: &CompletionConfig,
     position: FilePosition,
 ) -> Option<Completions> {
+    let _s = ra_prof::Scope::enter();
     let ctx = CompletionContext::new(db, position, config)?;
 
     let mut acc = Completions::default();

crates/ra_prof/Cargo.toml

@@ -24,4 +24,4 @@ cpu_profiler = []
 # Uncomment to enable for the whole crate graph
 # default = [ "backtrace" ]
 # default = [ "jemalloc" ]
-# default = [ "cpu_profiler" ]
+default = [ "cpu_profiler" ]

crates/ra_prof/src/lib.rs

@@ -66,7 +66,8 @@ impl Drop for Scope {
 /// 2. Build with `cpu_profiler` feature.
 /// 3. Tun the code, the *raw* output would be in the `./out.profile` file.
 /// 4. Install pprof for visualization (https://github.com/google/pprof).
-/// 5. Use something like `pprof -svg target/release/rust-analyzer ./out.profile` to see the results.
+/// 5. Bump sampling frequency to once per ms: `export CPUPROFILE_FREQUENCY=1000`
+/// 6. Use something like `pprof -svg target/release/rust-analyzer ./out.profile` to see the results.
 ///
 /// For example, here's how I run profiling on NixOS:
 ///
@@ -74,6 +75,10 @@ impl Drop for Scope {
 /// $ nix-shell -p gperftools --run \
 ///     'cargo run --release -p rust-analyzer -- parse < ~/projects/rustbench/parser.rs > /dev/null'
 /// ```
+///
+/// See this diff for how to profile completions:
+///
+/// https://github.com/rust-analyzer/rust-analyzer/pull/5306
 #[derive(Debug)]
 pub struct CpuProfiler {
     _private: (),