runtime/select.go optimize heapsort for lockorder

zikcheng · zikcheng · commit b8b00df4311f · 2023-10-23T19:08:35.000+08:00
Heapsort can stop when only one element remains in the heap.
diff --git a/src/runtime/select.go b/src/runtime/select.go
@@ -194,7 +194,7 @@ func selectgo(cas0 *scase, order0 *uint16, pc0 *uintptr, nsends, nrecvs int, blo
 		}
 		lockorder[j] = pollorder[i]
 	}
-	for i := len(lockorder) - 1; i >= 0; i-- {
+	for i := len(lockorder) - 1; i > 0; i-- {
 		o := lockorder[i]
 		c := scases[o].c
 		lockorder[i] = lockorder[0]

Original file line number	Diff line number	Diff line change
`@@ -194,7 +194,7 @@ func selectgo(cas0 scase, order0 uint16, pc0 *uintptr, nsends, nrecvs int, blo`
`194`	`194`	`}`
`195`	`195`	`lockorder[j] = pollorder[i]`
`196`	`196`	`}`
`197`		`- for i := len(lockorder) - 1; i >= 0; i-- {`
	`197`	`+ for i := len(lockorder) - 1; i > 0; i-- {`
`198`	`198`	`o := lockorder[i]`
`199`	`199`	`c := scases[o].c`
`200`	`200`	`lockorder[i] = lockorder[0]`