runtime: dump scheduler state if GODEBUG=schedtrace is set

The schedtrace value sets dump period in milliseconds.
In default mode the trace looks as follows:
SCHED 0ms: gomaxprocs=4 idleprocs=0 threads=3 idlethreads=0 runqueue=0 [1 0 0 0]
SCHED 1001ms: gomaxprocs=4 idleprocs=3 threads=6 idlethreads=3 runqueue=0 [0 0 0 0]
SCHED 2008ms: gomaxprocs=4 idleprocs=1 threads=6 idlethreads=1 runqueue=0 [0 1 0 0]
If GODEBUG=scheddetail=1 is set as well, then the detailed trace is printed:
SCHED 0ms: gomaxprocs=4 idleprocs=0 threads=3 idlethreads=0 runqueue=0 singleproc=0 gcwaiting=1 mlocked=0 nmspinning=0 stopwait=0 sysmonwait=0
  P0: status=3 tick=1 m=0 runqsize=1/128 gfreecnt=0
  P1: status=3 tick=0 m=-1 runqsize=0/128 gfreecnt=0
  P2: status=3 tick=0 m=-1 runqsize=0/128 gfreecnt=0
  P3: status=3 tick=0 m=-1 runqsize=0/128 gfreecnt=0
  M2: p=-1 curg=-1 mallocing=0 throwing=0 gcing=0 locks=1 dying=0 helpgc=0 spinning=0 lockedg=-1
  M1: p=-1 curg=-1 mallocing=0 throwing=0 gcing=0 locks=1 dying=0 helpgc=0 spinning=0 lockedg=-1
  M0: p=0 curg=1 mallocing=0 throwing=0 gcing=0 locks=1 dying=0 helpgc=0 spinning=0 lockedg=1
  G1: status=2() m=0 lockedm=0
  G2: status=1() m=-1 lockedm=-1

R=golang-dev, raggi, rsc
CC=golang-dev
https://golang.org/cl/11435044

1 files changed, 2 insertions, 0 deletions

diff --git a/src/pkg/runtime/runtime.c b/src/pkg/runtime/runtime.c
index 39bd9332e1..ab9fed805f 100644
--- a/src/pkg/runtime/runtime.c
+++ b/src/pkg/runtime/runtime.c
@@ -388,6 +388,8 @@ static struct {
 	int32*	value;
 } dbgvar[] = {
 	{"gctrace", &runtime·debug.gctrace},
+	{"schedtrace", &runtime·debug.schedtrace},
+	{"scheddetail", &runtime·debug.scheddetail},
 };
 
 void