Update parallel-rustc.md

Minor updates to syntax and improvements for readability.

Author: Tbkhi

src/parallel-rustc.md

@@ -1,22 +1,21 @@
 # Parallel Compilation
 
-As of <!-- date-check --> August 2022, the only stage of the compiler that 
-is already parallel is codegen. Some parts of the compiler already have 
-parallel implementations, such as query evaluation, type check and 
-monomorphization, but the general version of the compiler does not include 
-these parallelization functions. **To try out the current parallel compiler**, 
-one can install rustc from source code with `parallel-compiler = true` in 
-the `config.toml`.
+As of <!-- date-check --> August 2022, the only stage of the compiler that is
+parallel is codegen. Some parts of the compiler have parallel implementations,
+such as query evaluation, type check and [monomorphization][monomorphization],
+but the general version of the compiler does not include parallelization
+functions. **To try out the current parallel compiler**, install `rustc` from
+source code with `parallel-compiler = true` in the `Config.toml`.
 
 The lack of parallelism at other stages (for example, macro expansion) also 
 represents an opportunity for improving compiler performance.
 
 These next few sections describe where and how parallelism is currently used,
 and the current status of making parallel compilation the default in `rustc`.
 
-## Codegen
+## Code Generation
 
-During [monomorphization][monomorphization] the compiler splits up all the code to
+During monomorphization the compiler splits up all the code to
 be generated into smaller chunks called _codegen units_. These are then generated by
 independent instances of LLVM running in parallel. At the end, the linker
 is run to combine all the codegen units together into one binary. This process
@@ -45,22 +44,22 @@ are implemented differently depending on whether `parallel-compiler` is true.
 | LockGuard | parking_lot::MutexGuard | std::cell::RefMut |
 | MappedLockGuard | parking_lot::MappedMutexGuard | std::cell::RefMut |
 
-- These thread-safe data structures interspersed during compilation can 
-  cause a lot of lock contention, which actually degrades performance as the
-  number of threads increases beyond 4. This inspires us to audit the use 
-  of these data structures, leading to either refactoring to reduce use of 
-  shared state, or persistent documentation covering invariants, atomicity, 
-  and lock orderings.
+- These thread-safe data structures are interspersed during compilation which
+  can cause lock contention resulting in degraded performance as the number of
+  threads increases beyond 4. So we audit the use of these data structures
+  which leads to either a refactoring so as to reduce the use of shared state,
+  or the authoring of persistent documentation covering the specific of the
+  invariants, the atomicity, and the lock orderings.
 
 - On the other hand, we still need to figure out what other invariants 
   during compilation might not hold in parallel compilation.
 
 ### WorkLocal
 
-`WorkLocal` is a special data structure implemented for parallel compiler.
-It holds worker-locals values for each thread in a thread pool. You can only 
-access the worker local value through the Deref impl on the thread pool it 
-was constructed on. It will panic otherwise. 
+`WorkLocal` is a special data structure implemented for parallel compilers. It
+holds worker-locals values for each thread in a thread pool. You can only
+access the worker local value through the `Deref` `impl` on the thread pool it
+was constructed on. It panics otherwise. 
 
 `WorkLocal` is used to implement the `Arena` allocator in the parallel 
 environment, which is critical in parallel queries. Its implementation 
@@ -115,7 +114,7 @@ There are still many loops that have the potential to use parallel iterators.
 The query model has some properties that make it actually feasible to evaluate
 multiple queries in parallel without too much of an effort:
 
-- All data a query provider can access is accessed via the query context, so
+- All data a query provider can access is via the query context, so
   the query context can take care of synchronizing access.
 - Query results are required to be immutable so they can safely be used by
   different threads concurrently.
@@ -141,25 +140,24 @@ the previous `Data Structures` and `Parallel Iterators`. See [this tracking issu
 ## Rustdoc
 
 As of <!-- date-check--> November 2022, there are still a number of steps
-to complete before rustdoc rendering can be made parallel. More details on
-this issue can be found [here][parallel-rustdoc].
+to complete before `rustdoc` rendering can be made parallel (see a discussion of
+[parallel `rustdoc`][parallel-rustdoc]).
 
 ## Resources
 
-Here are some resources that can be used to learn more (note that some of them
-are a bit out of date):
+Here are some resources that can be used to learn more:
 
+- [This IRLO thread by alexchricton about performance][irlo1]
 - [This IRLO thread by Zoxc, one of the pioneers of the effort][irlo0]
 - [This list of interior mutability in the compiler by nikomatsakis][imlist]
-- [This IRLO thread by alexchricton about performance][irlo1]
 
 [`rayon`]: https://crates.io/crates/rayon
-[rustc-rayon]: https://github.com/rust-lang/rustc-rayon
-[irlo0]: https://internals.rust-lang.org/t/parallelizing-rustc-using-rayon/6606
+[Arc]: https://doc.rust-lang.org/std/sync/struct.Arc.html
 [imlist]: https://github.com/nikomatsakis/rustc-parallelization/blob/master/interior-mutability-list.md
+[irlo0]: https://internals.rust-lang.org/t/parallelizing-rustc-using-rayon/6606
 [irlo1]: https://internals.rust-lang.org/t/help-test-parallel-rustc/11503
-[tracking]: https://github.com/rust-lang/rust/issues/48685
 [monomorphization]: backend/monomorph.md
 [parallel-rustdoc]: https://github.com/rust-lang/rust/issues/82741
-[Arc]: https://doc.rust-lang.org/std/sync/struct.Arc.html
 [Rc]: https://doc.rust-lang.org/std/rc/struct.Rc.html
+[rustc-rayon]: https://github.com/rust-lang/rustc-rayon
+[tracking]: https://github.com/rust-lang/rust/issues/48685