runtime: capture per-g trace state in a type

More tightening up of the tracer's interface.

This increases the size of each G very slightly, which isn't great, but
we stay within the same size class, so actually memory use will be
unchanged.

Change-Id: I7d1f5798edcf437c212beb1e1a2619eab833aafb
Reviewed-on: https://go-review.googlesource.com/c/go/+/494188
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>

1 files changed, 24 insertions, 25 deletions

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 2cbc823fd9..9e702aa033 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -471,36 +471,35 @@ type g struct {
 	// for stack shrinking.
 	parkingOnChan atomic.Bool
 
-	raceignore     int8     // ignore race detection events
-	sysblocktraced bool     // StartTrace has emitted EvGoInSyscall about this goroutine
-	tracking       bool     // whether we're tracking this G for sched latency statistics
-	trackingSeq    uint8    // used to decide whether to track this G
-	trackingStamp  int64    // timestamp of when the G last started being tracked
-	runnableTime   int64    // the amount of time spent runnable, cleared when running, only used when tracking
-	sysexitticks   int64    // cputicks when syscall has returned (for tracing)
-	traceseq       uint64   // trace event sequencer
-	tracelastp     puintptr // last P emitted an event for this goroutine
-	lockedm        muintptr
-	sig            uint32
-	writebuf       []byte
-	sigcode0       uintptr
-	sigcode1       uintptr
-	sigpc          uintptr
-	parentGoid     uint64          // goid of goroutine that created this goroutine
-	gopc           uintptr         // pc of go statement that created this goroutine
-	ancestors      *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
-	startpc        uintptr         // pc of goroutine function
-	racectx        uintptr
-	waiting        *sudog         // sudog structures this g is waiting on (that have a valid elem ptr); in lock order
-	cgoCtxt        []uintptr      // cgo traceback context
-	labels         unsafe.Pointer // profiler labels
-	timer          *timer         // cached timer for time.Sleep
-	selectDone     atomic.Uint32  // are we participating in a select and did someone win the race?
+	raceignore    int8  // ignore race detection events
+	tracking      bool  // whether we're tracking this G for sched latency statistics
+	trackingSeq   uint8 // used to decide whether to track this G
+	trackingStamp int64 // timestamp of when the G last started being tracked
+	runnableTime  int64 // the amount of time spent runnable, cleared when running, only used when tracking
+	lockedm       muintptr
+	sig           uint32
+	writebuf      []byte
+	sigcode0      uintptr
+	sigcode1      uintptr
+	sigpc         uintptr
+	parentGoid    uint64          // goid of goroutine that created this goroutine
+	gopc          uintptr         // pc of go statement that created this goroutine
+	ancestors     *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
+	startpc       uintptr         // pc of goroutine function
+	racectx       uintptr
+	waiting       *sudog         // sudog structures this g is waiting on (that have a valid elem ptr); in lock order
+	cgoCtxt       []uintptr      // cgo traceback context
+	labels        unsafe.Pointer // profiler labels
+	timer         *timer         // cached timer for time.Sleep
+	selectDone    atomic.Uint32  // are we participating in a select and did someone win the race?
 
 	// goroutineProfiled indicates the status of this goroutine's stack for the
 	// current in-progress goroutine profile
 	goroutineProfiled goroutineProfileStateHolder
 
+	// Per-G tracer state.
+	trace gTraceState
+
 	// Per-G GC state
 
 	// gcAssistBytes is this G's GC assist credit in terms of