runtime: remove allocfreetrace

allocfreetrace prints all allocations and frees to stderr. It's not
terribly useful because it has a really huge overhead, making it not
feasible to use except for the most trivial programs. A follow-up CL
will replace it with something that is both more thorough and also lower
overhead.

Change-Id: I1d668fee8b6aaef5251a5aea3054ec2444d75eb6
Reviewed-on: https://go-review.googlesource.com/c/go/+/583376
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>

7 files changed, 6 insertions, 85 deletions

diff --git a/src/runtime/arena.go b/src/runtime/arena.go
index bb88ed053d..47b131466c 100644
--- a/src/runtime/arena.go
+++ b/src/runtime/arena.go
@@ -828,10 +828,6 @@ func newUserArenaChunk() (unsafe.Pointer, *mspan) {
 	}
 
 	if debug.malloc {
-		if debug.allocfreetrace != 0 {
-			tracealloc(unsafe.Pointer(span.base()), userArenaChunkBytes, nil)
-		}
-
 		if inittrace.active && inittrace.id == getg().goid {
 			// Init functions are executed sequentially in a single goroutine.
 			inittrace.bytes += uint64(userArenaChunkBytes)
diff --git a/src/runtime/extern.go b/src/runtime/extern.go
index 63950c3b5f..833019a7b4 100644
--- a/src/runtime/extern.go
+++ b/src/runtime/extern.go
@@ -35,9 +35,6 @@ time.
 The GODEBUG variable controls debugging variables within the runtime.
 It is a comma-separated list of name=val pairs setting these named variables:
 
-	allocfreetrace: setting allocfreetrace=1 causes every allocation to be
-	profiled and a stack trace printed on each object's allocation and free.
-
 	clobberfree: setting clobberfree=1 causes the garbage collector to
 	clobber the memory content of an object with bad content when it frees
 	the object.
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 48cace9171..a572900eb7 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1261,10 +1261,6 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
 	}
 
 	if debug.malloc {
-		if debug.allocfreetrace != 0 {
-			tracealloc(x, size, typ)
-		}
-
 		if inittrace.active && inittrace.id == getg().goid {
 			// Init functions are executed sequentially in a single goroutine.
 			inittrace.bytes += uint64(fullSize)
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 83afd55c47..1316af72ba 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1510,10 +1510,6 @@ func gcMarkWorkAvailable(p *p) bool {
 // All gcWork caches must be empty.
 // STW is in effect at this point.
 func gcMark(startTime int64) {
-	if debug.allocfreetrace > 0 {
-		tracegc()
-	}
-
 	if gcphase != _GCmarktermination {
 		throw("in gcMark expecting to see gcphase as _GCmarktermination")
 	}
diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go
index 5670b1b8d5..da66bfa596 100644
--- a/src/runtime/mgcsweep.go
+++ b/src/runtime/mgcsweep.go
@@ -608,17 +608,13 @@ func (sl *sweepLocked) sweep(preserve bool) bool {
 		spanHasNoSpecials(s)
 	}
 
-	if debug.allocfreetrace != 0 || debug.clobberfree != 0 || raceenabled || msanenabled || asanenabled {
-		// Find all newly freed objects. This doesn't have to
-		// efficient; allocfreetrace has massive overhead.
+	if debug.clobberfree != 0 || raceenabled || msanenabled || asanenabled {
+		// Find all newly freed objects.
 		mbits := s.markBitsForBase()
 		abits := s.allocBitsForIndex(0)
 		for i := uintptr(0); i < uintptr(s.nelems); i++ {
 			if !mbits.isMarked() && (abits.index < uintptr(s.freeindex) || abits.isMarked()) {
 				x := s.base() + i*s.elemsize
-				if debug.allocfreetrace != 0 {
-					tracefree(unsafe.Pointer(x), size)
-				}
 				if debug.clobberfree != 0 {
 					clobberfree(unsafe.Pointer(x), size)
 				}
diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go
index 87eed8d1dd..26b7d78283 100644
--- a/src/runtime/mprof.go
+++ b/src/runtime/mprof.go
@@ -1459,61 +1459,3 @@ func Stack(buf []byte, all bool) int {
 	}
 	return n
 }
-
-// Tracing of alloc/free/gc.
-
-var tracelock mutex
-
-func tracealloc(p unsafe.Pointer, size uintptr, typ *_type) {
-	lock(&tracelock)
-	gp := getg()
-	gp.m.traceback = 2
-	if typ == nil {
-		print("tracealloc(", p, ", ", hex(size), ")\n")
-	} else {
-		print("tracealloc(", p, ", ", hex(size), ", ", toRType(typ).string(), ")\n")
-	}
-	if gp.m.curg == nil || gp == gp.m.curg {
-		goroutineheader(gp)
-		pc := getcallerpc()
-		sp := getcallersp()
-		systemstack(func() {
-			traceback(pc, sp, 0, gp)
-		})
-	} else {
-		goroutineheader(gp.m.curg)
-		traceback(^uintptr(0), ^uintptr(0), 0, gp.m.curg)
-	}
-	print("\n")
-	gp.m.traceback = 0
-	unlock(&tracelock)
-}
-
-func tracefree(p unsafe.Pointer, size uintptr) {
-	lock(&tracelock)
-	gp := getg()
-	gp.m.traceback = 2
-	print("tracefree(", p, ", ", hex(size), ")\n")
-	goroutineheader(gp)
-	pc := getcallerpc()
-	sp := getcallersp()
-	systemstack(func() {
-		traceback(pc, sp, 0, gp)
-	})
-	print("\n")
-	gp.m.traceback = 0
-	unlock(&tracelock)
-}
-
-func tracegc() {
-	lock(&tracelock)
-	gp := getg()
-	gp.m.traceback = 2
-	print("tracegc()\n")
-	// running on m->g0 stack; show all non-g0 goroutines
-	tracebackothers(gp)
-	print("end tracegc\n")
-	print("\n")
-	gp.m.traceback = 0
-	unlock(&tracelock)
-}
diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
index 5b37d23e90..dd19242cb4 100644
--- a/src/runtime/runtime1.go
+++ b/src/runtime/runtime1.go
@@ -334,10 +334,9 @@ var debug struct {
 	// debug.malloc is used as a combined debug check
 	// in the malloc function and should be set
 	// if any of the below debug options is != 0.
-	malloc         bool
-	allocfreetrace int32
-	inittrace      int32
-	sbrk           int32
+	malloc    bool
+	inittrace int32
+	sbrk      int32
 
 	panicnil atomic.Int32
 
@@ -354,7 +353,6 @@ var debug struct {
 
 var dbgvars = []*dbgVar{
 	{name: "adaptivestackstart", value: &debug.adaptivestackstart},
-	{name: "allocfreetrace", value: &debug.allocfreetrace},
 	{name: "asyncpreemptoff", value: &debug.asyncpreemptoff},
 	{name: "asynctimerchan", atomic: &debug.asynctimerchan},
 	{name: "cgocheck", value: &debug.cgocheck},
@@ -425,7 +423,7 @@ func parsedebugvars() {
 	// apply environment settings
 	parsegodebug(godebug, nil)
 
-	debug.malloc = (debug.allocfreetrace | debug.inittrace | debug.sbrk) != 0
+	debug.malloc = (debug.inittrace | debug.sbrk) != 0
 
 	setTraceback(gogetenv("GOTRACEBACK"))
 	traceback_env = traceback_cache