[dev.typeparams] runtime: simplify defer record allocation

Now that deferred functions are always argumentless and defer
records are no longer with arguments, defer record can be fixed
size (just the _defer struct). This allows us to simplify the
allocation of defer records, specifically, remove the defer
classes and the pools of different sized defers.

Change-Id: Icc4b16afc23b38262ca9dd1f7369ad40874cf701
Reviewed-on: https://go-review.googlesource.com/c/go/+/326062
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 8 insertions, 10 deletions

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index c239fa0f63..34b5b482a3 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1558,19 +1558,17 @@ func clearpools() {
 	sched.sudogcache = nil
 	unlock(&sched.sudoglock)
 
-	// Clear central defer pools.
+	// Clear central defer pool.
 	// Leave per-P pools alone, they have strictly bounded size.
 	lock(&sched.deferlock)
-	for i := range sched.deferpool {
-		// disconnect cached list before dropping it on the floor,
-		// so that a dangling ref to one entry does not pin all of them.
-		var d, dlink *_defer
-		for d = sched.deferpool[i]; d != nil; d = dlink {
-			dlink = d.link
-			d.link = nil
-		}
-		sched.deferpool[i] = nil
+	// disconnect cached list before dropping it on the floor,
+	// so that a dangling ref to one entry does not pin all of them.
+	var d, dlink *_defer
+	for d = sched.deferpool; d != nil; d = dlink {
+		dlink = d.link
+		d.link = nil
 	}
+	sched.deferpool = nil
 	unlock(&sched.deferlock)
 }