runtime: reduced struct sizes found via pahole

During my research of pahole with Go structs, I've found couple of
structs in runtime/ pkg where we can reduce several structs' sizes
highligted by pahole tool which detect byte holes and paddings.

Overall, there are 80 bytes reduced.

Change-Id: I398e5ed6f5b199394307741981cb5ad5b875e98f
Reviewed-on: https://go-review.googlesource.com/c/go/+/578795
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Joedian Reid <joedian@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/mgclimit.go

@@ -33,16 +33,6 @@ type gcCPULimiterState struct {
 	lock atomic.Uint32
 
 	enabled atomic.Bool
-	bucket  struct {
-		// Invariants:
-		// - fill >= 0
-		// - capacity >= 0
-		// - fill <= capacity
-		fill, capacity uint64
-	}
-	// overflow is the cumulative amount of GC CPU time that we tried to fill the
-	// bucket with but exceeded its capacity.
-	overflow uint64
 
 	// gcEnabled is an internal copy of gcBlackenEnabled that determines
 	// whether the limiter tracks total assist time.
@@ -55,6 +45,20 @@ type gcCPULimiterState struct {
 	// the mark and sweep phases.
 	transitioning bool
 
+	// test indicates whether this instance of the struct was made for testing purposes.
+	test bool
+
+	bucket struct {
+		// Invariants:
+		// - fill >= 0
+		// - capacity >= 0
+		// - fill <= capacity
+		fill, capacity uint64
+	}
+	// overflow is the cumulative amount of GC CPU time that we tried to fill the
+	// bucket with but exceeded its capacity.
+	overflow uint64
+
 	// assistTimePool is the accumulated assist time since the last update.
 	assistTimePool atomic.Int64
 
@@ -77,9 +81,6 @@ type gcCPULimiterState struct {
 	//
 	// gomaxprocs isn't used directly so as to keep this structure unit-testable.
 	nprocs int32
-
-	// test indicates whether this instance of the struct was made for testing purposes.
-	test bool
 }
 
 // limiting returns true if the CPU limiter is currently enabled, meaning the Go GC

src/runtime/mgcscavenge.go

@@ -281,15 +281,19 @@ type scavengerState struct {
 	// g is the goroutine the scavenger is bound to.
 	g *g
 
-	// parked is whether or not the scavenger is parked.
-	parked bool
-
 	// timer is the timer used for the scavenger to sleep.
 	timer *timer
 
 	// sysmonWake signals to sysmon that it should wake the scavenger.
 	sysmonWake atomic.Uint32
 
+	// parked is whether or not the scavenger is parked.
+	parked bool
+
+	// printControllerReset instructs printScavTrace to signal that
+	// the controller was reset.
+	printControllerReset bool
+
 	// targetCPUFraction is the target CPU overhead for the scavenger.
 	targetCPUFraction float64
 
@@ -312,10 +316,6 @@ type scavengerState struct {
 	// value. Used if the controller's assumptions fail to hold.
 	controllerCooldown int64
 
-	// printControllerReset instructs printScavTrace to signal that
-	// the controller was reset.
-	printControllerReset bool
-
 	// sleepStub is a stub used for testing to avoid actually having
 	// the scavenger sleep.
 	//

src/runtime/netpoll.go

@@ -102,14 +102,14 @@ type pollDesc struct {
 
 	lock    mutex // protects the following fields
 	closing bool
+	rrun    bool      // whether rt is running
+	wrun    bool      // whether wt is running
 	user    uint32    // user settable cookie
 	rseq    uintptr   // protects from stale read timers
 	rt      timer     // read deadline timer
-	rrun    bool      // whether rt is running
 	rd      int64     // read deadline (a nanotime in the future, -1 when expired)
 	wseq    uintptr   // protects from stale write timers
 	wt      timer     // write deadline timer
-	wrun    bool      // whether wt is running
 	wd      int64     // write deadline (a nanotime in the future, -1 when expired)
 	self    *pollDesc // storage for indirect interface. See (*pollDesc).makeArg.
 }

src/runtime/proc.go

@@ -6024,8 +6024,8 @@ func sysmon() {
 
 type sysmontick struct {
 	schedtick   uint32
-	schedwhen   int64
 	syscalltick uint32
+	schedwhen   int64
 	syscallwhen int64
 }
 

src/runtime/runtime2.go

@@ -510,12 +510,12 @@ type g struct {
 	sleepWhen     int64          // when to sleep until
 	selectDone    atomic.Uint32  // are we participating in a select and did someone win the race?
 
-	coroarg *coro // argument during coroutine transfers
-
 	// goroutineProfiled indicates the status of this goroutine's stack for the
 	// current in-progress goroutine profile
 	goroutineProfiled goroutineProfileStateHolder
 
+	coroarg *coro // argument during coroutine transfers
+
 	// Per-G tracer state.
 	trace gTraceState
 
@@ -604,8 +604,8 @@ type m struct {
 	// there's no stack to put them on. That is their sole purpose.
 	waitunlockf          func(*g, unsafe.Pointer) bool
 	waitlock             unsafe.Pointer
-	waitTraceBlockReason traceBlockReason
 	waitTraceSkip        int
+	waitTraceBlockReason traceBlockReason
 
 	syscalltick uint32
 	freelink    *m // on sched.freem

src/runtime/sizeof_test.go

@@ -20,7 +20,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr // size on 32bit platforms
 		_64bit uintptr // size on 64bit platforms
 	}{
-		{runtime.G{}, 272, 440},   // g, but exported for testing
+		{runtime.G{}, 272, 432},   // g, but exported for testing
 		{runtime.Sudog{}, 56, 88}, // sudog, but exported for testing
 	}
 

src/runtime/symtab.go

@@ -401,13 +401,12 @@ type moduledata struct {
 	modulehashes []modulehash
 
 	hasmain uint8 // 1 if module contains the main function, 0 otherwise
+	bad     bool  // module failed to load and should be ignored
 
 	gcdatamask, gcbssmask bitvector
 
 	typemap map[typeOff]*_type // offset to *_rtype in previous module
 
-	bad bool // module failed to load and should be ignored
-
 	next *moduledata
 }