Merge pull request #1482 from nnethercote/update-perf-runner

Update perf runner details

Author: nnethercote

collector/README.md

@@ -1,7 +1,8 @@
 # Rust Compiler Performance Benchmarking and Profiling
 
 Hardware and software details of the machine that executes the CI details can be found
-[here](perf-runner.md). 
+[here](../docs/perf-runner.md). A glossary of relevant terms can be found
+[here](../docs/glossary.md).
 
 ## The benchmarks
 

collector/perf-runner.md renamed to docs/perf-runner.md

@@ -42,11 +42,12 @@ The machine that actually executes the benchmarks in CI has the following config
 - OS: Ubuntu `18.04`
 
 ## Configuration
-### Turboboost
-Enabled.
+### HyperThreading & Turboboost
+As of November 2022, both are disabled.
 
-### HyperThreading
-Enabled.
+Prior to October 2022, both were enabled. During October 2022 some
+[experimentation](https://github.com/rust-lang/rustc-perf/issues/1450) was done
+which found that disabling both reduced variance significantly.
 
 ### CPU scaling
 Scaling governor set to `performance`.