From 1a411e201b71374f515d1f6cdbb1b36186ee48b0 Mon Sep 17 00:00:00 2001
From: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Date: Mon, 8 May 2023 21:32:17 -0700
Subject: Add some comments

---
 src/bundler/bundle_v2.zig | 5 +++++
 src/fs.zig                | 8 ++++++++
 2 files changed, 13 insertions(+)

(limited to 'src')

diff --git a/src/bundler/bundle_v2.zig b/src/bundler/bundle_v2.zig
index 9502f5dfe..aad40b961 100644
--- a/src/bundler/bundle_v2.zig
+++ b/src/bundler/bundle_v2.zig
@@ -1750,6 +1750,11 @@ pub const BundleV2 = struct {
     }
 
     // TODO: remove ResolveQueue
+    //
+    // Moving this to the Bundle thread was a significant perf improvement on Linux for first builds
+    //
+    // The problem is that module resolution has many mutexes.
+    // The downside is cached resolutions are faster to do in threads since they only lock very briefly.
     fn runResolutionForParseTask(parse_result: *ParseTask.Result, this: *BundleV2) ResolveQueue {
         var ast = &parse_result.value.success.ast;
         const source = &parse_result.value.success.source;
diff --git a/src/fs.zig b/src/fs.zig
index ee2fdff54..f85678136 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -885,6 +885,14 @@ pub const FileSystem = struct {
             return readDirectoryWithIterator(fs, _dir, _handle, generation, store_fd, void, {});
         }
 
+        // One of the learnings here
+        //
+        //   Closing file descriptors yields significant performance benefits on Linux
+        //
+        // It was literally a 300% performance improvement to bundling.
+        // https://twitter.com/jarredsumner/status/1655787337027309568
+        // https://twitter.com/jarredsumner/status/1655714084569120770
+        // https://twitter.com/jarredsumner/status/1655464485245845506
         pub fn readDirectoryWithIterator(fs: *RealFS, _dir: string, _handle: ?std.fs.Dir, generation: bun.Generation, store_fd: bool, comptime Iterator: type, iterator: Iterator) !*EntriesOption {
             var dir = _dir;
             var cache_result: ?allocators.Result = null;
-- 
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