runtime: use internal/trace/tracev2 definitions

This change deduplicates trace wire format definitions between the
runtime and the trace parser by making the internal/trace/tracev2
package the source of truth.

Change-Id: Ia0721d3484a80417e40ac473ec32870bee73df09
Reviewed-on: https://go-review.googlesource.com/c/go/+/644221
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

13 files changed, 152 insertions, 306 deletions

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index d7d97ad244..d10f3c09cf 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1553,7 +1553,7 @@ func gcBgMarkWorker(ready chan struct{}) {
 		// We'll releasem after this point and thus this P may run
 		// something else. We must clear the worker mode to avoid
 		// attributing the mode to a different (non-worker) G in
-		// traceGoStart.
+		// tracev2.GoStart.
 		pp.gcMarkWorkerMode = gcMarkWorkerNotWorker
 
 		// If this worker reached a background mark completion
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index e9873e54cd..ce6cf88d0c 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -4693,7 +4693,7 @@ func exitsyscall() {
 				trace.GoSysExit(lostP)
 				if lostP {
 					// We lost the P at some point, even though we got it back here.
-					// Trace that we're starting again, because there was a traceGoSysBlock
+					// Trace that we're starting again, because there was a tracev2.GoSysBlock
 					// call somewhere in exitsyscallfast (indicating that this goroutine
 					// had blocked) and we're about to start running again.
 					trace.GoStart()
@@ -4790,7 +4790,7 @@ func exitsyscallfast_reacquired(trace traceLocker) {
 	if gp.m.syscalltick != gp.m.p.ptr().syscalltick {
 		if trace.ok() {
 			// The p was retaken and then enter into syscall again (since gp.m.syscalltick has changed).
-			// traceGoSysBlock for this syscall was already emitted,
+			// tracev2.GoSysBlock for this syscall was already emitted,
 			// but here we effectively retake the p from the new syscall running on the same p.
 			systemstack(func() {
 				// We're stealing the P. It's treated
diff --git a/src/runtime/traceallocfree.go b/src/runtime/traceallocfree.go
index 84188a55c4..40f1cfe8ab 100644
--- a/src/runtime/traceallocfree.go
+++ b/src/runtime/traceallocfree.go
@@ -9,6 +9,7 @@ package runtime
 import (
 	"internal/abi"
 	"internal/runtime/sys"
+	"internal/trace/tracev2"
 )
 
 // Batch type values for the alloc/free experiment.
@@ -27,7 +28,7 @@ func traceSnapshotMemory(gen uintptr) {
 	// Write a batch containing information that'll be necessary to
 	// interpret the events.
 	var flushed bool
-	w := unsafeTraceExpWriter(gen, nil, traceExperimentAllocFree)
+	w := unsafeTraceExpWriter(gen, nil, tracev2.AllocFree)
 	w, flushed = w.ensure(1 + 4*traceBytesPerNumber)
 	if flushed {
 		// Annotate the batch as containing additional info.
@@ -89,17 +90,17 @@ func traceSpanTypeAndClass(s *mspan) traceArg {
 
 // SpanExists records an event indicating that the span exists.
 func (tl traceLocker) SpanExists(s *mspan) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvSpan, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpan, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
 }
 
 // SpanAlloc records an event indicating that the span has just been allocated.
 func (tl traceLocker) SpanAlloc(s *mspan) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvSpanAlloc, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpanAlloc, traceSpanID(s), traceArg(s.npages), traceSpanTypeAndClass(s))
 }
 
 // SpanFree records an event indicating that the span is about to be freed.
 func (tl traceLocker) SpanFree(s *mspan) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvSpanFree, traceSpanID(s))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSpanFree, traceSpanID(s))
 }
 
 // traceSpanID creates a trace ID for the span s for the trace.
@@ -111,19 +112,19 @@ func traceSpanID(s *mspan) traceArg {
 // The type is optional, and the size of the slot occupied the object is inferred from the
 // span containing it.
 func (tl traceLocker) HeapObjectExists(addr uintptr, typ *abi.Type) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvHeapObject, traceHeapObjectID(addr), tl.rtype(typ))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObject, traceHeapObjectID(addr), tl.rtype(typ))
 }
 
 // HeapObjectAlloc records that an object was newly allocated at addr with the provided type.
 // The type is optional, and the size of the slot occupied the object is inferred from the
 // span containing it.
 func (tl traceLocker) HeapObjectAlloc(addr uintptr, typ *abi.Type) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvHeapObjectAlloc, traceHeapObjectID(addr), tl.rtype(typ))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObjectAlloc, traceHeapObjectID(addr), tl.rtype(typ))
 }
 
 // HeapObjectFree records that an object at addr is about to be freed.
 func (tl traceLocker) HeapObjectFree(addr uintptr) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvHeapObjectFree, traceHeapObjectID(addr))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapObjectFree, traceHeapObjectID(addr))
 }
 
 // traceHeapObjectID creates a trace ID for a heap object at address addr.
@@ -134,18 +135,18 @@ func traceHeapObjectID(addr uintptr) traceArg {
 // GoroutineStackExists records that a goroutine stack already exists at address base with the provided size.
 func (tl traceLocker) GoroutineStackExists(base, size uintptr) {
 	order := traceCompressStackSize(size)
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoroutineStack, traceGoroutineStackID(base), order)
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStack, traceGoroutineStackID(base), order)
 }
 
 // GoroutineStackAlloc records that a goroutine stack was newly allocated at address base with the provided size..
 func (tl traceLocker) GoroutineStackAlloc(base, size uintptr) {
 	order := traceCompressStackSize(size)
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoroutineStackAlloc, traceGoroutineStackID(base), order)
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStackAlloc, traceGoroutineStackID(base), order)
 }
 
 // GoroutineStackFree records that a goroutine stack at address base is about to be freed.
 func (tl traceLocker) GoroutineStackFree(base uintptr) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoroutineStackFree, traceGoroutineStackID(base))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoroutineStackFree, traceGoroutineStackID(base))
 }
 
 // traceGoroutineStackID creates a trace ID for the goroutine stack from its base address.
diff --git a/src/runtime/tracebuf.go b/src/runtime/tracebuf.go
index 0849a57809..63803a90f5 100644
--- a/src/runtime/tracebuf.go
+++ b/src/runtime/tracebuf.go
@@ -8,6 +8,7 @@ package runtime
 
 import (
 	"internal/runtime/sys"
+	"internal/trace/tracev2"
 	"unsafe"
 )
 
@@ -24,7 +25,7 @@ const traceBytesPerNumber = 10
 // we can change it if it's deemed too error-prone.
 type traceWriter struct {
 	traceLocker
-	exp traceExperiment
+	exp tracev2.Experiment
 	*traceBuf
 }
 
@@ -48,7 +49,7 @@ func (tl traceLocker) writer() traceWriter {
 			gp.throwsplit = true
 		}
 	}
-	return traceWriter{traceLocker: tl, traceBuf: tl.mp.trace.buf[tl.gen%2][traceNoExperiment]}
+	return traceWriter{traceLocker: tl, traceBuf: tl.mp.trace.buf[tl.gen%2][tracev2.NoExperiment]}
 }
 
 // unsafeTraceWriter produces a traceWriter that doesn't lock the trace.
@@ -70,7 +71,7 @@ func unsafeTraceWriter(gen uintptr, buf *traceBuf) traceWriter {
 // have any stack growth.
 //
 //go:nosplit
-func (w traceWriter) event(ev traceEv, args ...traceArg) traceWriter {
+func (w traceWriter) event(ev tracev2.EventType, args ...traceArg) traceWriter {
 	// N.B. Everything in this call must be nosplit to maintain
 	// the stack growth related invariants for writing events.
 
@@ -186,10 +187,10 @@ func (w traceWriter) refill() traceWriter {
 	}
 
 	// Write the buffer's header.
-	if w.exp == traceNoExperiment {
-		w.byte(byte(traceEvEventBatch))
+	if w.exp == tracev2.NoExperiment {
+		w.byte(byte(tracev2.EvEventBatch))
 	} else {
-		w.byte(byte(traceEvExperimentalBatch))
+		w.byte(byte(tracev2.EvExperimentalBatch))
 		w.byte(byte(w.exp))
 	}
 	w.varint(uint64(w.gen))
@@ -199,6 +200,27 @@ func (w traceWriter) refill() traceWriter {
 	return w
 }
 
+// expWriter returns a traceWriter that writes into the current M's stream for
+// the given experiment.
+func (tl traceLocker) expWriter(exp tracev2.Experiment) traceWriter {
+	return traceWriter{traceLocker: tl, traceBuf: tl.mp.trace.buf[tl.gen%2][exp], exp: exp}
+}
+
+// unsafeTraceExpWriter produces a traceWriter for experimental trace batches
+// that doesn't lock the trace. Data written to experimental batches need not
+// conform to the standard trace format.
+//
+// It should only be used in contexts where either:
+// - Another traceLocker is held.
+// - trace.gen is prevented from advancing.
+//
+// This does not have the same stack growth restrictions as traceLocker.writer.
+//
+// buf may be nil.
+func unsafeTraceExpWriter(gen uintptr, buf *traceBuf, exp tracev2.Experiment) traceWriter {
+	return traceWriter{traceLocker: traceLocker{gen: gen}, traceBuf: buf, exp: exp}
+}
+
 // traceBufQueue is a FIFO of traceBufs.
 type traceBufQueue struct {
 	head, tail *traceBuf
@@ -247,7 +269,7 @@ type traceBufHeader struct {
 type traceBuf struct {
 	_ sys.NotInHeap
 	traceBufHeader
-	arr [64<<10 - unsafe.Sizeof(traceBufHeader{})]byte // underlying buffer for traceBufHeader.buf
+	arr [tracev2.MaxBatchSize - unsafe.Sizeof(traceBufHeader{})]byte // underlying buffer for traceBufHeader.buf
 }
 
 // byte appends v to buf.
diff --git a/src/runtime/tracecpu.go b/src/runtime/tracecpu.go
index c8a6f56ff2..092c707f83 100644
--- a/src/runtime/tracecpu.go
+++ b/src/runtime/tracecpu.go
@@ -6,6 +6,8 @@
 
 package runtime
 
+import "internal/trace/tracev2"
+
 // traceInitReadCPU initializes CPU profile -> tracer state for tracing.
 //
 // Returns a profBuf for reading from.
@@ -114,7 +116,7 @@ func traceStopReadCPU() {
 // Must not run on the system stack because profBuf.read performs race
 // operations.
 func traceReadCPU(gen uintptr) bool {
-	var pcBuf [traceStackSize]uintptr
+	var pcBuf [tracev2.MaxFramesPerStack]uintptr
 
 	data, tags, eof := trace.cpuLogRead[gen%2].read(profBufNonBlocking)
 	for len(data) > 0 {
@@ -169,17 +171,17 @@ func traceReadCPU(gen uintptr) bool {
 
 		// Ensure we have a place to write to.
 		var flushed bool
-		w, flushed = w.ensure(2 + 5*traceBytesPerNumber /* traceEvCPUSamples + traceEvCPUSample + timestamp + g + m + p + stack ID */)
+		w, flushed = w.ensure(2 + 5*traceBytesPerNumber /* tracev2.EvCPUSamples + tracev2.EvCPUSample + timestamp + g + m + p + stack ID */)
 		if flushed {
 			// Annotate the batch as containing strings.
-			w.byte(byte(traceEvCPUSamples))
+			w.byte(byte(tracev2.EvCPUSamples))
 		}
 
 		// Add the stack to the table.
 		stackID := trace.stackTab[gen%2].put(pcBuf[:nstk])
 
 		// Write out the CPU sample.
-		w.byte(byte(traceEvCPUSample))
+		w.byte(byte(tracev2.EvCPUSample))
 		w.varint(timestamp)
 		w.varint(mpid)
 		w.varint(ppid)
diff --git a/src/runtime/traceevent.go b/src/runtime/traceevent.go
index 51d2368842..9d1a93d3f9 100644
--- a/src/runtime/traceevent.go
+++ b/src/runtime/traceevent.go
@@ -9,88 +9,7 @@ package runtime
 import (
 	"internal/abi"
 	"internal/runtime/sys"
-)
-
-// Event types in the trace, args are given in square brackets.
-//
-// Naming scheme:
-//   - Time range event pairs have suffixes "Begin" and "End".
-//   - "Start", "Stop", "Create", "Destroy", "Block", "Unblock"
-//     are suffixes reserved for scheduling resources.
-//
-// NOTE: If you add an event type, make sure you also update all
-// tables in this file!
-type traceEv uint8
-
-const (
-	traceEvNone traceEv = iota // unused
-
-	// Structural events.
-	traceEvEventBatch // start of per-M batch of events [generation, M ID, timestamp, batch length]
-	traceEvStacks     // start of a section of the stack table [...traceEvStack]
-	traceEvStack      // stack table entry [ID, ...{PC, func string ID, file string ID, line #}]
-	traceEvStrings    // start of a section of the string dictionary [...traceEvString]
-	traceEvString     // string dictionary entry [ID, length, string]
-	traceEvCPUSamples // start of a section of CPU samples [...traceEvCPUSample]
-	traceEvCPUSample  // CPU profiling sample [timestamp, M ID, P ID, goroutine ID, stack ID]
-	traceEvFrequency  // timestamp units per sec [freq]
-
-	// Procs.
-	traceEvProcsChange // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack ID]
-	traceEvProcStart   // start of P [timestamp, P ID, P seq]
-	traceEvProcStop    // stop of P [timestamp]
-	traceEvProcSteal   // P was stolen [timestamp, P ID, P seq, M ID]
-	traceEvProcStatus  // P status at the start of a generation [timestamp, P ID, status]
-
-	// Goroutines.
-	traceEvGoCreate            // goroutine creation [timestamp, new goroutine ID, new stack ID, stack ID]
-	traceEvGoCreateSyscall     // goroutine appears in syscall (cgo callback) [timestamp, new goroutine ID]
-	traceEvGoStart             // goroutine starts running [timestamp, goroutine ID, goroutine seq]
-	traceEvGoDestroy           // goroutine ends [timestamp]
-	traceEvGoDestroySyscall    // goroutine ends in syscall (cgo callback) [timestamp]
-	traceEvGoStop              // goroutine yields its time, but is runnable [timestamp, reason, stack ID]
-	traceEvGoBlock             // goroutine blocks [timestamp, reason, stack ID]
-	traceEvGoUnblock           // goroutine is unblocked [timestamp, goroutine ID, goroutine seq, stack ID]
-	traceEvGoSyscallBegin      // syscall enter [timestamp, P seq, stack ID]
-	traceEvGoSyscallEnd        // syscall exit [timestamp]
-	traceEvGoSyscallEndBlocked // syscall exit and it blocked at some point [timestamp]
-	traceEvGoStatus            // goroutine status at the start of a generation [timestamp, goroutine ID, M ID, status]
-
-	// STW.
-	traceEvSTWBegin // STW start [timestamp, kind]
-	traceEvSTWEnd   // STW done [timestamp]
-
-	// GC events.
-	traceEvGCActive           // GC active [timestamp, seq]
-	traceEvGCBegin            // GC start [timestamp, seq, stack ID]
-	traceEvGCEnd              // GC done [timestamp, seq]
-	traceEvGCSweepActive      // GC sweep active [timestamp, P ID]
-	traceEvGCSweepBegin       // GC sweep start [timestamp, stack ID]
-	traceEvGCSweepEnd         // GC sweep done [timestamp, swept bytes, reclaimed bytes]
-	traceEvGCMarkAssistActive // GC mark assist active [timestamp, goroutine ID]
-	traceEvGCMarkAssistBegin  // GC mark assist start [timestamp, stack ID]
-	traceEvGCMarkAssistEnd    // GC mark assist done [timestamp]
-	traceEvHeapAlloc          // gcController.heapLive change [timestamp, heap alloc in bytes]
-	traceEvHeapGoal           // gcController.heapGoal() change [timestamp, heap goal in bytes]
-
-	// Annotations.
-	traceEvGoLabel         // apply string label to current running goroutine [timestamp, label string ID]
-	traceEvUserTaskBegin   // trace.NewTask [timestamp, internal task ID, internal parent task ID, name string ID, stack ID]
-	traceEvUserTaskEnd     // end of a task [timestamp, internal task ID, stack ID]
-	traceEvUserRegionBegin // trace.{Start,With}Region [timestamp, internal task ID, name string ID, stack ID]
-	traceEvUserRegionEnd   // trace.{End,With}Region [timestamp, internal task ID, name string ID, stack ID]
-	traceEvUserLog         // trace.Log [timestamp, internal task ID, key string ID, stack, value string ID]
-
-	// Coroutines.
-	traceEvGoSwitch        // goroutine switch (coroswitch) [timestamp, goroutine ID, goroutine seq]
-	traceEvGoSwitchDestroy // goroutine switch and destroy [timestamp, goroutine ID, goroutine seq]
-	traceEvGoCreateBlocked // goroutine creation (starts blocked) [timestamp, new goroutine ID, new stack ID, stack ID]
-
-	// GoStatus with stack.
-	traceEvGoStatusStack // goroutine status at the start of a generation, with a stack [timestamp, goroutine ID, M ID, status, stack ID]
-
-	// Batch event for an experimental batch with a custom format.
-	traceEvExperimentalBatch // start of extra data [experiment ID, generation, M ID, timestamp, batch length, batch data...]
+	"internal/trace/tracev2"
 )
 
 // traceArg is a simple wrapper type to help ensure that arguments passed
@@ -117,8 +36,8 @@ type traceEventWriter struct {
 // been Runnable before a GoStart). Otherwise, callers can query the status of either the goroutine
 // or P and pass the appropriate status.
 //
-// In this case, the default status should be traceGoBad or traceProcBad to help identify bugs sooner.
-func (tl traceLocker) eventWriter(goStatus traceGoStatus, procStatus traceProcStatus) traceEventWriter {
+// In this case, the default status should be tracev2.GoBad or tracev2.ProcBad to help identify bugs sooner.
+func (tl traceLocker) eventWriter(goStatus tracev2.GoStatus, procStatus tracev2.ProcStatus) traceEventWriter {
 	if pp := tl.mp.p.ptr(); pp != nil && !pp.trace.statusWasTraced(tl.gen) && pp.trace.acquireStatus(tl.gen) {
 		tl.writer().writeProcStatus(uint64(pp.id), procStatus, pp.trace.inSweep).end()
 	}
@@ -129,7 +48,7 @@ func (tl traceLocker) eventWriter(goStatus traceGoStatus, procStatus traceProcSt
 }
 
 // event writes out a trace event.
-func (e traceEventWriter) event(ev traceEv, args ...traceArg) {
+func (e traceEventWriter) event(ev tracev2.EventType, args ...traceArg) {
 	e.tl.writer().event(ev, args...).end()
 }
 
diff --git a/src/runtime/traceexp.go b/src/runtime/traceexp.go
deleted file mode 100644
index 13eec0c0b6..0000000000
--- a/src/runtime/traceexp.go
+++ /dev/null
@@ -1,63 +0,0 @@
-// Copyright 2024 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package runtime
-
-// expWriter returns a traceWriter that writes into the current M's stream for
-// the given experiment.
-func (tl traceLocker) expWriter(exp traceExperiment) traceWriter {
-	return traceWriter{traceLocker: tl, traceBuf: tl.mp.trace.buf[tl.gen%2][exp], exp: exp}
-}
-
-// unsafeTraceExpWriter produces a traceWriter for experimental trace batches
-// that doesn't lock the trace. Data written to experimental batches need not
-// conform to the standard trace format.
-//
-// It should only be used in contexts where either:
-// - Another traceLocker is held.
-// - trace.gen is prevented from advancing.
-//
-// This does not have the same stack growth restrictions as traceLocker.writer.
-//
-// buf may be nil.
-func unsafeTraceExpWriter(gen uintptr, buf *traceBuf, exp traceExperiment) traceWriter {
-	return traceWriter{traceLocker: traceLocker{gen: gen}, traceBuf: buf, exp: exp}
-}
-
-// traceExperiment is an enumeration of the different kinds of experiments supported for tracing.
-type traceExperiment uint8
-
-const (
-	// traceNoExperiment indicates no experiment.
-	traceNoExperiment traceExperiment = iota
-
-	// traceExperimentAllocFree is an experiment to add alloc/free events to the trace.
-	traceExperimentAllocFree
-
-	// traceNumExperiments is the number of trace experiments (and 1 higher than
-	// the highest numbered experiment).
-	traceNumExperiments
-)
-
-// Experimental events.
-const (
-	_ traceEv = 127 + iota
-
-	// Experimental events for ExperimentAllocFree.
-
-	// Experimental heap span events. IDs map reversibly to base addresses.
-	traceEvSpan      // heap span exists [timestamp, id, npages, type/class]
-	traceEvSpanAlloc // heap span alloc [timestamp, id, npages, type/class]
-	traceEvSpanFree  // heap span free [timestamp, id]
-
-	// Experimental heap object events. IDs map reversibly to addresses.
-	traceEvHeapObject      // heap object exists [timestamp, id, type]
-	traceEvHeapObjectAlloc // heap object alloc [timestamp, id, type]
-	traceEvHeapObjectFree  // heap object free [timestamp, id]
-
-	// Experimental goroutine stack events. IDs map reversibly to addresses.
-	traceEvGoroutineStack      // stack exists [timestamp, id, order]
-	traceEvGoroutineStackAlloc // stack alloc [timestamp, id, order]
-	traceEvGoroutineStackFree  // stack free [timestamp, id]
-)
diff --git a/src/runtime/traceruntime.go b/src/runtime/traceruntime.go
index 284e61301b..98ac1082a8 100644
--- a/src/runtime/traceruntime.go
+++ b/src/runtime/traceruntime.go
@@ -8,6 +8,7 @@ package runtime
 
 import (
 	"internal/runtime/atomic"
+	"internal/trace/tracev2"
 	_ "unsafe" // for go:linkname
 )
 
@@ -24,11 +25,11 @@ func (s *gTraceState) reset() {
 
 // mTraceState is per-M state for the tracer.
 type mTraceState struct {
-	seqlock       atomic.Uintptr                    // seqlock indicating that this M is writing to a trace buffer.
-	buf           [2][traceNumExperiments]*traceBuf // Per-M traceBuf for writing. Indexed by trace.gen%2.
-	link          *m                                // Snapshot of alllink or freelink.
-	reentered     uint32                            // Whether we've reentered tracing from within tracing.
-	oldthrowsplit bool                              // gp.throwsplit upon calling traceLocker.writer. For debugging.
+	seqlock       atomic.Uintptr                       // seqlock indicating that this M is writing to a trace buffer.
+	buf           [2][tracev2.NumExperiments]*traceBuf // Per-M traceBuf for writing. Indexed by trace.gen%2.
+	link          *m                                   // Snapshot of alllink or freelink.
+	reentered     uint32                               // Whether we've reentered tracing from within tracing.
+	oldthrowsplit bool                                 // gp.throwsplit upon calling traceLocker.writer. For debugging.
 }
 
 // pTraceState is per-P state for the tracer.
@@ -283,7 +284,7 @@ func traceExitedSyscall() {
 
 // Gomaxprocs emits a ProcsChange event.
 func (tl traceLocker) Gomaxprocs(procs int32) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvProcsChange, traceArg(procs), tl.stack(1))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvProcsChange, traceArg(procs), tl.stack(1))
 }
 
 // ProcStart traces a ProcStart event.
@@ -294,14 +295,14 @@ func (tl traceLocker) ProcStart() {
 	// Procs are typically started within the scheduler when there is no user goroutine. If there is a user goroutine,
 	// it must be in _Gsyscall because the only time a goroutine is allowed to have its Proc moved around from under it
 	// is during a syscall.
-	tl.eventWriter(traceGoSyscall, traceProcIdle).event(traceEvProcStart, traceArg(pp.id), pp.trace.nextSeq(tl.gen))
+	tl.eventWriter(tracev2.GoSyscall, tracev2.ProcIdle).event(tracev2.EvProcStart, traceArg(pp.id), pp.trace.nextSeq(tl.gen))
 }
 
 // ProcStop traces a ProcStop event.
 func (tl traceLocker) ProcStop(pp *p) {
 	// The only time a goroutine is allowed to have its Proc moved around
 	// from under it is during a syscall.
-	tl.eventWriter(traceGoSyscall, traceProcRunning).event(traceEvProcStop)
+	tl.eventWriter(tracev2.GoSyscall, tracev2.ProcRunning).event(tracev2.EvProcStop)
 }
 
 // GCActive traces a GCActive event.
@@ -309,7 +310,7 @@ func (tl traceLocker) ProcStop(pp *p) {
 // Must be emitted by an actively running goroutine on an active P. This restriction can be changed
 // easily and only depends on where it's currently called.
 func (tl traceLocker) GCActive() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCActive, traceArg(trace.seqGC))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCActive, traceArg(trace.seqGC))
 	// N.B. Only one GC can be running at a time, so this is naturally
 	// serialized by the caller.
 	trace.seqGC++
@@ -320,7 +321,7 @@ func (tl traceLocker) GCActive() {
 // Must be emitted by an actively running goroutine on an active P. This restriction can be changed
 // easily and only depends on where it's currently called.
 func (tl traceLocker) GCStart() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCBegin, traceArg(trace.seqGC), tl.stack(3))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCBegin, traceArg(trace.seqGC), tl.stack(3))
 	// N.B. Only one GC can be running at a time, so this is naturally
 	// serialized by the caller.
 	trace.seqGC++
@@ -331,7 +332,7 @@ func (tl traceLocker) GCStart() {
 // Must be emitted by an actively running goroutine on an active P. This restriction can be changed
 // easily and only depends on where it's currently called.
 func (tl traceLocker) GCDone() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCEnd, traceArg(trace.seqGC))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCEnd, traceArg(trace.seqGC))
 	// N.B. Only one GC can be running at a time, so this is naturally
 	// serialized by the caller.
 	trace.seqGC++
@@ -341,14 +342,14 @@ func (tl traceLocker) GCDone() {
 func (tl traceLocker) STWStart(reason stwReason) {
 	// Although the current P may be in _Pgcstop here, we model the P as running during the STW. This deviates from the
 	// runtime's state tracking, but it's more accurate and doesn't result in any loss of information.
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvSTWBegin, tl.string(reason.String()), tl.stack(2))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSTWBegin, tl.string(reason.String()), tl.stack(2))
 }
 
 // STWDone traces a STWEnd event.
 func (tl traceLocker) STWDone() {
 	// Although the current P may be in _Pgcstop here, we model the P as running during the STW. This deviates from the
 	// runtime's state tracking, but it's more accurate and doesn't result in any loss of information.
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvSTWEnd)
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvSTWEnd)
 }
 
 // GCSweepStart prepares to trace a sweep loop. This does not
@@ -380,7 +381,7 @@ func (tl traceLocker) GCSweepSpan(bytesSwept uintptr) {
 	pp := tl.mp.p.ptr()
 	if pp.trace.maySweep {
 		if pp.trace.swept == 0 {
-			tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCSweepBegin, tl.stack(1))
+			tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCSweepBegin, tl.stack(1))
 			pp.trace.inSweep = true
 		}
 		pp.trace.swept += bytesSwept
@@ -398,7 +399,7 @@ func (tl traceLocker) GCSweepDone() {
 		throw("missing traceGCSweepStart")
 	}
 	if pp.trace.inSweep {
-		tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCSweepEnd, traceArg(pp.trace.swept), traceArg(pp.trace.reclaimed))
+		tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCSweepEnd, traceArg(pp.trace.swept), traceArg(pp.trace.reclaimed))
 		pp.trace.inSweep = false
 	}
 	pp.trace.maySweep = false
@@ -406,22 +407,22 @@ func (tl traceLocker) GCSweepDone() {
 
 // GCMarkAssistStart emits a MarkAssistBegin event.
 func (tl traceLocker) GCMarkAssistStart() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCMarkAssistBegin, tl.stack(1))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCMarkAssistBegin, tl.stack(1))
 }
 
 // GCMarkAssistDone emits a MarkAssistEnd event.
 func (tl traceLocker) GCMarkAssistDone() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGCMarkAssistEnd)
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGCMarkAssistEnd)
 }
 
 // GoCreate emits a GoCreate event.
 func (tl traceLocker) GoCreate(newg *g, pc uintptr, blocked bool) {
 	newg.trace.setStatusTraced(tl.gen)
-	ev := traceEvGoCreate
+	ev := tracev2.EvGoCreate
 	if blocked {
-		ev = traceEvGoCreateBlocked
+		ev = tracev2.EvGoCreateBlocked
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(ev, traceArg(newg.goid), tl.startPC(pc), tl.stack(2))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(ev, traceArg(newg.goid), tl.startPC(pc), tl.stack(2))
 }
 
 // GoStart emits a GoStart event.
@@ -430,10 +431,10 @@ func (tl traceLocker) GoCreate(newg *g, pc uintptr, blocked bool) {
 func (tl traceLocker) GoStart() {
 	gp := getg().m.curg
 	pp := gp.m.p
-	w := tl.eventWriter(traceGoRunnable, traceProcRunning)
-	w.event(traceEvGoStart, traceArg(gp.goid), gp.trace.nextSeq(tl.gen))
+	w := tl.eventWriter(tracev2.GoRunnable, tracev2.ProcRunning)
+	w.event(tracev2.EvGoStart, traceArg(gp.goid), gp.trace.nextSeq(tl.gen))
 	if pp.ptr().gcMarkWorkerMode != gcMarkWorkerNotWorker {
-		w.event(traceEvGoLabel, trace.markWorkerLabels[tl.gen%2][pp.ptr().gcMarkWorkerMode])
+		w.event(tracev2.EvGoLabel, trace.markWorkerLabels[tl.gen%2][pp.ptr().gcMarkWorkerMode])
 	}
 }
 
@@ -441,7 +442,7 @@ func (tl traceLocker) GoStart() {
 //
 // TODO(mknyszek): Rename this to GoDestroy.
 func (tl traceLocker) GoEnd() {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoDestroy)
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoDestroy)
 }
 
 // GoSched emits a GoStop event with a GoSched reason.
@@ -456,7 +457,7 @@ func (tl traceLocker) GoPreempt() {
 
 // GoStop emits a GoStop event with the provided reason.
 func (tl traceLocker) GoStop(reason traceGoStopReason) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoStop, traceArg(trace.goStopReasons[tl.gen%2][reason]), tl.stack(1))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoStop, traceArg(trace.goStopReasons[tl.gen%2][reason]), tl.stack(1))
 }
 
 // GoPark emits a GoBlock event with the provided reason.
@@ -464,14 +465,14 @@ func (tl traceLocker) GoStop(reason traceGoStopReason) {
 // TODO(mknyszek): Replace traceBlockReason with waitReason. It's silly
 // that we have both, and waitReason is way more descriptive.
 func (tl traceLocker) GoPark(reason traceBlockReason, skip int) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoBlock, traceArg(trace.goBlockReasons[tl.gen%2][reason]), tl.stack(skip))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoBlock, traceArg(trace.goBlockReasons[tl.gen%2][reason]), tl.stack(skip))
 }
 
 // GoUnpark emits a GoUnblock event.
 func (tl traceLocker) GoUnpark(gp *g, skip int) {
 	// Emit a GoWaiting status if necessary for the unblocked goroutine.
 	tl.emitUnblockStatus(gp, tl.gen)
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoUnblock, traceArg(gp.goid), gp.trace.nextSeq(tl.gen), tl.stack(skip))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoUnblock, traceArg(gp.goid), gp.trace.nextSeq(tl.gen), tl.stack(skip))
 }
 
 // GoSwitch emits a GoSwitch event. If destroy is true, the calling goroutine
@@ -479,10 +480,10 @@ func (tl traceLocker) GoUnpark(gp *g, skip int) {
 func (tl traceLocker) GoSwitch(nextg *g, destroy bool) {
 	// Emit a GoWaiting status if necessary for the unblocked goroutine.
 	tl.emitUnblockStatus(nextg, tl.gen)
-	w := tl.eventWriter(traceGoRunning, traceProcRunning)
-	ev := traceEvGoSwitch
+	w := tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning)
+	ev := tracev2.EvGoSwitch
 	if destroy {
-		ev = traceEvGoSwitchDestroy
+		ev = tracev2.EvGoSwitchDestroy
 	}
 	w.event(ev, traceArg(nextg.goid), nextg.trace.nextSeq(tl.gen))
 }
@@ -494,7 +495,7 @@ func (tl traceLocker) emitUnblockStatus(gp *g, gen uintptr) {
 		// TODO(go.dev/issue/65634): Although it would be nice to add a stack trace here of gp,
 		// we cannot safely do so. gp is in _Gwaiting and so we don't have ownership of its stack.
 		// We can fix this by acquiring the goroutine's scan bit.
-		tl.writer().writeGoStatus(gp.goid, -1, traceGoWaiting, gp.inMarkAssist, 0).end()
+		tl.writer().writeGoStatus(gp.goid, -1, tracev2.GoWaiting, gp.inMarkAssist, 0).end()
 	}
 }
 
@@ -505,7 +506,7 @@ func (tl traceLocker) GoSysCall() {
 	// Scribble down the M that the P is currently attached to.
 	pp := tl.mp.p.ptr()
 	pp.trace.mSyscallID = int64(tl.mp.procid)
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvGoSyscallBegin, pp.trace.nextSeq(tl.gen), tl.stack(1))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvGoSyscallBegin, pp.trace.nextSeq(tl.gen), tl.stack(1))
 }
 
 // GoSysExit emits a GoSyscallEnd event, possibly along with a GoSyscallBlocked event
@@ -518,15 +519,15 @@ func (tl traceLocker) GoSysCall() {
 // - The goroutine lost its P and was unable to reacquire it, and is now running without a P.
 // - The goroutine lost its P and acquired a different one, and is now running with that P.
 func (tl traceLocker) GoSysExit(lostP bool) {
-	ev := traceEvGoSyscallEnd
-	procStatus := traceProcSyscall // Procs implicitly enter traceProcSyscall on GoSyscallBegin.
+	ev := tracev2.EvGoSyscallEnd
+	procStatus := tracev2.ProcSyscall // Procs implicitly enter tracev2.ProcSyscall on GoSyscallBegin.
 	if lostP {
-		ev = traceEvGoSyscallEndBlocked
-		procStatus = traceProcRunning // If a G has a P when emitting this event, it reacquired a P and is indeed running.
+		ev = tracev2.EvGoSyscallEndBlocked
+		procStatus = tracev2.ProcRunning // If a G has a P when emitting this event, it reacquired a P and is indeed running.
 	} else {
 		tl.mp.p.ptr().trace.mSyscallID = -1
 	}
-	tl.eventWriter(traceGoSyscall, procStatus).event(ev)
+	tl.eventWriter(tracev2.GoSyscall, procStatus).event(ev)
 }
 
 // ProcSteal indicates that our current M stole a P from another M.
@@ -547,7 +548,7 @@ func (tl traceLocker) ProcSteal(pp *p, inSyscall bool) {
 	if !pp.trace.statusWasTraced(tl.gen) && pp.trace.acquireStatus(tl.gen) {
 		// Careful: don't use the event writer. We never want status or in-progress events
 		// to trigger more in-progress events.
-		tl.writer().writeProcStatus(uint64(pp.id), traceProcSyscallAbandoned, pp.trace.inSweep).end()
+		tl.writer().writeProcStatus(uint64(pp.id), tracev2.ProcSyscallAbandoned, pp.trace.inSweep).end()
 	}
 
 	// The status of the proc and goroutine, if we need to emit one here, is not evident from the
@@ -556,18 +557,18 @@ func (tl traceLocker) ProcSteal(pp *p, inSyscall bool) {
 	// ourselves specifically to keep running. The two contexts look different, but can be summarized
 	// fairly succinctly. In the former, we're a regular running goroutine and proc, if we have either.
 	// In the latter, we're a goroutine in a syscall.
-	goStatus := traceGoRunning
-	procStatus := traceProcRunning
+	goStatus := tracev2.GoRunning
+	procStatus := tracev2.ProcRunning
 	if inSyscall {
-		goStatus = traceGoSyscall
-		procStatus = traceProcSyscallAbandoned
+		goStatus = tracev2.GoSyscall
+		procStatus = tracev2.ProcSyscallAbandoned
 	}
-	tl.eventWriter(goStatus, procStatus).event(traceEvProcSteal, traceArg(pp.id), pp.trace.nextSeq(tl.gen), traceArg(mStolenFrom))
+	tl.eventWriter(goStatus, procStatus).event(tracev2.EvProcSteal, traceArg(pp.id), pp.trace.nextSeq(tl.gen), traceArg(mStolenFrom))
 }
 
 // HeapAlloc emits a HeapAlloc event.
 func (tl traceLocker) HeapAlloc(live uint64) {
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvHeapAlloc, traceArg(live))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapAlloc, traceArg(live))
 }
 
 // HeapGoal reads the current heap goal and emits a HeapGoal event.
@@ -577,7 +578,7 @@ func (tl traceLocker) HeapGoal() {
 		// Heap-based triggering is disabled.
 		heapGoal = 0
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvHeapGoal, traceArg(heapGoal))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvHeapGoal, traceArg(heapGoal))
 }
 
 // GoCreateSyscall indicates that a goroutine has transitioned from dead to GoSyscall.
@@ -590,7 +591,7 @@ func (tl traceLocker) GoCreateSyscall(gp *g) {
 	// N.B. We should never trace a status for this goroutine (which we're currently running on),
 	// since we want this to appear like goroutine creation.
 	gp.trace.setStatusTraced(tl.gen)
-	tl.eventWriter(traceGoBad, traceProcBad).event(traceEvGoCreateSyscall, traceArg(gp.goid))
+	tl.eventWriter(tracev2.GoBad, tracev2.ProcBad).event(tracev2.EvGoCreateSyscall, traceArg(gp.goid))
 }
 
 // GoDestroySyscall indicates that a goroutine has transitioned from GoSyscall to dead.
@@ -602,7 +603,7 @@ func (tl traceLocker) GoCreateSyscall(gp *g) {
 func (tl traceLocker) GoDestroySyscall() {
 	// N.B. If we trace a status here, we must never have a P, and we must be on a goroutine
 	// that is in the syscall state.
-	tl.eventWriter(traceGoSyscall, traceProcBad).event(traceEvGoDestroySyscall)
+	tl.eventWriter(tracev2.GoSyscall, tracev2.ProcBad).event(tracev2.EvGoDestroySyscall)
 }
 
 // To access runtime functions from runtime/trace.
@@ -617,7 +618,7 @@ func trace_userTaskCreate(id, parentID uint64, taskType string) {
 		// Need to do this check because the caller won't have it.
 		return
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvUserTaskBegin, traceArg(id), traceArg(parentID), tl.string(taskType), tl.stack(3))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvUserTaskBegin, traceArg(id), traceArg(parentID), tl.string(taskType), tl.stack(3))
 	traceRelease(tl)
 }
 
@@ -630,7 +631,7 @@ func trace_userTaskEnd(id uint64) {
 		// Need to do this check because the caller won't have it.
 		return
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvUserTaskEnd, traceArg(id), tl.stack(2))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvUserTaskEnd, traceArg(id), tl.stack(2))
 	traceRelease(tl)
 }
 
@@ -646,16 +647,16 @@ func trace_userRegion(id, mode uint64, name string) {
 		// Need to do this check because the caller won't have it.
 		return
 	}
-	var ev traceEv
+	var ev tracev2.EventType
 	switch mode {
 	case 0:
-		ev = traceEvUserRegionBegin
+		ev = tracev2.EvUserRegionBegin
 	case 1:
-		ev = traceEvUserRegionEnd
+		ev = tracev2.EvUserRegionEnd
 	default:
 		return
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(ev, traceArg(id), tl.string(name), tl.stack(3))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(ev, traceArg(id), tl.string(name), tl.stack(3))
 	traceRelease(tl)
 }
 
@@ -668,7 +669,7 @@ func trace_userLog(id uint64, category, message string) {
 		// Need to do this check because the caller won't have it.
 		return
 	}
-	tl.eventWriter(traceGoRunning, traceProcRunning).event(traceEvUserLog, traceArg(id), tl.string(category), tl.uniqueString(message), tl.stack(3))
+	tl.eventWriter(tracev2.GoRunning, tracev2.ProcRunning).event(tracev2.EvUserLog, traceArg(id), tl.string(category), tl.uniqueString(message), tl.stack(3))
 	traceRelease(tl)
 }
 
diff --git a/src/runtime/tracestack.go b/src/runtime/tracestack.go
index 225566d102..bca2d0a88d 100644
--- a/src/runtime/tracestack.go
+++ b/src/runtime/tracestack.go
@@ -9,15 +9,11 @@ package runtime
 import (
 	"internal/abi"
 	"internal/goarch"
+	"internal/trace/tracev2"
 	"unsafe"
 )
 
 const (
-	// Maximum number of PCs in a single stack trace.
-	// Since events contain only stack id rather than whole stack trace,
-	// we can allow quite large values here.
-	traceStackSize = 128
-
 	// logicalStackSentinel is a sentinel value at pcBuf[0] signifying that
 	// pcBuf[1:] holds a logical stack requiring no further processing. Any other
 	// value at pcBuf[0] represents a skip value to apply to the physical stack in
@@ -36,7 +32,7 @@ const (
 // that this stack trace is being written out for, which needs to be synchronized with
 // generations moving forward. Prefer traceEventWriter.stack.
 func traceStack(skip int, gp *g, gen uintptr) uint64 {
-	var pcBuf [traceStackSize]uintptr
+	var pcBuf [tracev2.MaxFramesPerStack]uintptr
 
 	// Figure out gp and mp for the backtrace.
 	var mp *m
@@ -55,7 +51,7 @@ func traceStack(skip int, gp *g, gen uintptr) uint64 {
 			// are totally fine for taking a stack trace. They're captured
 			// correctly in goStatusToTraceGoStatus.
 			switch goStatusToTraceGoStatus(status, gp.waitreason) {
-			case traceGoRunning, traceGoSyscall:
+			case tracev2.GoRunning, tracev2.GoSyscall:
 				if getg() == gp || mp.curg == gp {
 					break
 				}
@@ -147,7 +143,7 @@ func (t *traceStackTable) put(pcs []uintptr) uint64 {
 // releases all memory and resets state. It must only be called once the caller
 // can guarantee that there are no more writers to the table.
 func (t *traceStackTable) dump(gen uintptr) {
-	stackBuf := make([]uintptr, traceStackSize)
+	stackBuf := make([]uintptr, tracev2.MaxFramesPerStack)
 	w := unsafeTraceWriter(gen, nil)
 	if root := (*traceMapNode)(t.tab.root.Load()); root != nil {
 		w = dumpStacksRec(root, w, stackBuf)
@@ -172,15 +168,15 @@ func dumpStacksRec(node *traceMapNode, w traceWriter, stackBuf []uintptr) traceW
 	// bound is pretty loose, but avoids counting
 	// lots of varint sizes.
 	//
-	// Add 1 because we might also write traceEvStacks.
+	// Add 1 because we might also write tracev2.EvStacks.
 	var flushed bool
 	w, flushed = w.ensure(1 + maxBytes)
 	if flushed {
-		w.byte(byte(traceEvStacks))
+		w.byte(byte(tracev2.EvStacks))
 	}
 
 	// Emit stack event.
-	w.byte(byte(traceEvStack))
+	w.byte(byte(tracev2.EvStack))
 	w.varint(uint64(node.id))
 	w.varint(uint64(len(frames)))
 	for _, frame := range frames {
diff --git a/src/runtime/tracestatus.go b/src/runtime/tracestatus.go
index 425ac37ba0..4dabc8e562 100644
--- a/src/runtime/tracestatus.go
+++ b/src/runtime/tracestatus.go
@@ -6,43 +6,9 @@
 
 package runtime
 
-import "internal/runtime/atomic"
-
-// traceGoStatus is the status of a goroutine.
-//
-// They correspond directly to the various goroutine
-// statuses.
-type traceGoStatus uint8
-
-const (
-	traceGoBad traceGoStatus = iota
-	traceGoRunnable
-	traceGoRunning
-	traceGoSyscall
-	traceGoWaiting
-)
-
-// traceProcStatus is the status of a P.
-//
-// They mostly correspond to the various P statuses.
-type traceProcStatus uint8
-
-const (
-	traceProcBad traceProcStatus = iota
-	traceProcRunning
-	traceProcIdle
-	traceProcSyscall
-
-	// traceProcSyscallAbandoned is a special case of
-	// traceProcSyscall. It's used in the very specific case
-	// where the first a P is mentioned in a generation is
-	// part of a ProcSteal event. If that's the first time
-	// it's mentioned, then there's no GoSyscallBegin to
-	// connect the P stealing back to at that point. This
-	// special state indicates this to the parser, so it
-	// doesn't try to find a GoSyscallEndBlocked that
-	// corresponds with the ProcSteal.
-	traceProcSyscallAbandoned
+import (
+	"internal/runtime/atomic"
+	"internal/trace/tracev2"
 )
 
 // writeGoStatus emits a GoStatus event as well as any active ranges on the goroutine.
@@ -51,23 +17,23 @@ const (
 // have any stack growth.
 //
 //go:nosplit
-func (w traceWriter) writeGoStatus(goid uint64, mid int64, status traceGoStatus, markAssist bool, stackID uint64) traceWriter {
+func (w traceWriter) writeGoStatus(goid uint64, mid int64, status tracev2.GoStatus, markAssist bool, stackID uint64) traceWriter {
 	// The status should never be bad. Some invariant must have been violated.
-	if status == traceGoBad {
+	if status == tracev2.GoBad {
 		print("runtime: goid=", goid, "\n")
 		throw("attempted to trace a bad status for a goroutine")
 	}
 
 	// Trace the status.
 	if stackID == 0 {
-		w = w.event(traceEvGoStatus, traceArg(goid), traceArg(uint64(mid)), traceArg(status))
+		w = w.event(tracev2.EvGoStatus, traceArg(goid), traceArg(uint64(mid)), traceArg(status))
 	} else {
-		w = w.event(traceEvGoStatusStack, traceArg(goid), traceArg(uint64(mid)), traceArg(status), traceArg(stackID))
+		w = w.event(tracev2.EvGoStatusStack, traceArg(goid), traceArg(uint64(mid)), traceArg(status), traceArg(stackID))
 	}
 
 	// Trace any special ranges that are in-progress.
 	if markAssist {
-		w = w.event(traceEvGCMarkAssistActive, traceArg(goid))
+		w = w.event(tracev2.EvGCMarkAssistActive, traceArg(goid))
 	}
 	return w
 }
@@ -85,26 +51,26 @@ func (w traceWriter) writeProcStatusForP(pp *p, inSTW bool) traceWriter {
 	if !pp.trace.acquireStatus(w.gen) {
 		return w
 	}
-	var status traceProcStatus
+	var status tracev2.ProcStatus
 	switch pp.status {
 	case _Pidle, _Pgcstop:
-		status = traceProcIdle
+		status = tracev2.ProcIdle
 		if pp.status == _Pgcstop && inSTW {
 			// N.B. a P that is running and currently has the world stopped will be
 			// in _Pgcstop, but we model it as running in the tracer.
-			status = traceProcRunning
+			status = tracev2.ProcRunning
 		}
 	case _Prunning:
-		status = traceProcRunning
+		status = tracev2.ProcRunning
 		// There's a short window wherein the goroutine may have entered _Gsyscall
 		// but it still owns the P (it's not in _Psyscall yet). The goroutine entering
 		// _Gsyscall is the tracer's signal that the P its bound to is also in a syscall,
 		// so we need to emit a status that matches. See #64318.
 		if w.mp.p.ptr() == pp && w.mp.curg != nil && readgstatus(w.mp.curg)&^_Gscan == _Gsyscall {
-			status = traceProcSyscall
+			status = tracev2.ProcSyscall
 		}
 	case _Psyscall:
-		status = traceProcSyscall
+		status = tracev2.ProcSyscall
 	default:
 		throw("attempt to trace invalid or unsupported P status")
 	}
@@ -121,19 +87,19 @@ func (w traceWriter) writeProcStatusForP(pp *p, inSTW bool) traceWriter {
 // have any stack growth.
 //
 //go:nosplit
-func (w traceWriter) writeProcStatus(pid uint64, status traceProcStatus, inSweep bool) traceWriter {
+func (w traceWriter) writeProcStatus(pid uint64, status tracev2.ProcStatus, inSweep bool) traceWriter {
 	// The status should never be bad. Some invariant must have been violated.
-	if status == traceProcBad {
+	if status == tracev2.ProcBad {
 		print("runtime: pid=", pid, "\n")
 		throw("attempted to trace a bad status for a proc")
 	}
 
 	// Trace the status.
-	w = w.event(traceEvProcStatus, traceArg(pid), traceArg(status))
+	w = w.event(tracev2.EvProcStatus, traceArg(pid), traceArg(status))
 
 	// Trace any special ranges that are in-progress.
 	if inSweep {
-		w = w.event(traceEvGCSweepActive, traceArg(pid))
+		w = w.event(tracev2.EvGCSweepActive, traceArg(pid))
 	}
 	return w
 }
@@ -146,16 +112,16 @@ func (w traceWriter) writeProcStatus(pid uint64, status traceProcStatus, inSweep
 // have any stack growth.
 //
 //go:nosplit
-func goStatusToTraceGoStatus(status uint32, wr waitReason) traceGoStatus {
+func goStatusToTraceGoStatus(status uint32, wr waitReason) tracev2.GoStatus {
 	// N.B. Ignore the _Gscan bit. We don't model it in the tracer.
-	var tgs traceGoStatus
+	var tgs tracev2.GoStatus
 	switch status &^ _Gscan {
 	case _Grunnable:
-		tgs = traceGoRunnable
+		tgs = tracev2.GoRunnable
 	case _Grunning, _Gcopystack:
-		tgs = traceGoRunning
+		tgs = tracev2.GoRunning
 	case _Gsyscall:
-		tgs = traceGoSyscall
+		tgs = tracev2.GoSyscall
 	case _Gwaiting, _Gpreempted:
 		// There are a number of cases where a G might end up in
 		// _Gwaiting but it's actually running in a non-preemptive
@@ -163,9 +129,9 @@ func goStatusToTraceGoStatus(status uint32, wr waitReason) traceGoStatus {
 		// garbage collector. In these cases, we're not going to
 		// emit an event, and we want these goroutines to appear in
 		// the final trace as if they're running, not blocked.
-		tgs = traceGoWaiting
+		tgs = tracev2.GoWaiting
 		if status == _Gwaiting && wr.isWaitingForGC() {
-			tgs = traceGoRunning
+			tgs = tracev2.GoRunning
 		}
 	case _Gdead:
 		throw("tried to trace dead goroutine")
diff --git a/src/runtime/tracestring.go b/src/runtime/tracestring.go
index 2585c69cc0..d486f9efbd 100644
--- a/src/runtime/tracestring.go
+++ b/src/runtime/tracestring.go
@@ -6,9 +6,9 @@
 
 package runtime
 
-// Trace strings.
+import "internal/trace/tracev2"
 
-const maxTraceStringLen = 1024
+// Trace strings.
 
 // traceStringTable is map of string -> unique ID that also manages
 // writing strings out into the trace.
@@ -52,8 +52,8 @@ func (t *traceStringTable) emit(gen uintptr, s string) uint64 {
 //go:systemstack
 func (t *traceStringTable) writeString(gen uintptr, id uint64, s string) {
 	// Truncate the string if necessary.
-	if len(s) > maxTraceStringLen {
-		s = s[:maxTraceStringLen]
+	if len(s) > tracev2.MaxEventTrailerDataSize {
+		s = s[:tracev2.MaxEventTrailerDataSize]
 	}
 
 	lock(&t.lock)
@@ -61,14 +61,14 @@ func (t *traceStringTable) writeString(gen uintptr, id uint64, s string) {
 
 	// Ensure we have a place to write to.
 	var flushed bool
-	w, flushed = w.ensure(2 + 2*traceBytesPerNumber + len(s) /* traceEvStrings + traceEvString + ID + len + string data */)
+	w, flushed = w.ensure(2 + 2*traceBytesPerNumber + len(s) /* tracev2.EvStrings + tracev2.EvString + ID + len + string data */)
 	if flushed {
 		// Annotate the batch as containing strings.
-		w.byte(byte(traceEvStrings))
+		w.byte(byte(tracev2.EvStrings))
 	}
 
 	// Write out the string.
-	w.byte(byte(traceEvString))
+	w.byte(byte(tracev2.EvString))
 	w.varint(id)
 	w.varint(uint64(len(s)))
 	w.stringData(s)
diff --git a/src/runtime/tracetime.go b/src/runtime/tracetime.go
index d5ee2b078f..bfda0aac9a 100644
--- a/src/runtime/tracetime.go
+++ b/src/runtime/tracetime.go
@@ -8,6 +8,7 @@ package runtime
 
 import (
 	"internal/goarch"
+	"internal/trace/tracev2"
 	_ "unsafe"
 )
 
@@ -80,10 +81,10 @@ func traceFrequency(gen uintptr) {
 	w := unsafeTraceWriter(gen, nil)
 
 	// Ensure we have a place to write to.
-	w, _ = w.ensure(1 + traceBytesPerNumber /* traceEvFrequency + frequency */)
+	w, _ = w.ensure(1 + traceBytesPerNumber /* tracev2.EvFrequency + frequency */)
 
 	// Write out the string.
-	w.byte(byte(traceEvFrequency))
+	w.byte(byte(tracev2.EvFrequency))
 	w.varint(traceClockUnitsPerSecond())
 
 	// Immediately flush the buffer.
diff --git a/src/runtime/tracetype.go b/src/runtime/tracetype.go
index d9e340f64a..f54f812578 100644
--- a/src/runtime/tracetype.go
+++ b/src/runtime/tracetype.go
@@ -9,6 +9,7 @@ package runtime
 import (
 	"internal/abi"
 	"internal/goarch"
+	"internal/trace/tracev2"
 	"unsafe"
 )
 
@@ -35,7 +36,7 @@ func (t *traceTypeTable) put(typ *abi.Type) uint64 {
 // releases all memory and resets state. It must only be called once the caller
 // can guarantee that there are no more writers to the table.
 func (t *traceTypeTable) dump(gen uintptr) {
-	w := unsafeTraceExpWriter(gen, nil, traceExperimentAllocFree)
+	w := unsafeTraceExpWriter(gen, nil, tracev2.AllocFree)
 	if root := (*traceMapNode)(t.tab.root.Load()); root != nil {
 		w = dumpTypesRec(root, w)
 	}