runtime: add per-pause gc stats

R=r, r2
CC=golang-dev
https://golang.org/cl/3980042

3 files changed, 14 insertions, 7 deletions

diff --git a/src/pkg/runtime/debug.go b/src/pkg/runtime/debug.go
index 3ce35cc5ba..cf30374f09 100644
--- a/src/pkg/runtime/debug.go
+++ b/src/pkg/runtime/debug.go
@@ -39,6 +39,7 @@ type MemStatsType struct {
 	Sys        uint64 // bytes obtained from system (should be sum of XxxSys below)
 	Lookups    uint64 // number of pointer lookups
 	Mallocs    uint64 // number of mallocs
+	Frees      uint64 // number of frees
 
 	// Main allocation heap statistics.
 	HeapAlloc   uint64 // bytes allocated and still in use
@@ -60,11 +61,12 @@ type MemStatsType struct {
 	BuckHashSys uint64 // profiling bucket hash table
 
 	// Garbage collector statistics.
-	NextGC   uint64
-	PauseNs  uint64
-	NumGC    uint32
-	EnableGC bool
-	DebugGC  bool
+	NextGC       uint64
+	PauseTotalNs uint64
+	PauseNs      [256]uint64 // most recent GC pause times
+	NumGC        uint32
+	EnableGC     bool
+	DebugGC      bool
 
 	// Per-size allocation statistics.
 	// Not locked during update; approximate.
diff --git a/src/pkg/runtime/malloc.h b/src/pkg/runtime/malloc.h
index 0cee6c0ddb..7e750b9170 100644
--- a/src/pkg/runtime/malloc.h
+++ b/src/pkg/runtime/malloc.h
@@ -176,6 +176,7 @@ struct MStats
 	uint64	sys;		// bytes obtained from system (should be sum of xxx_sys below)
 	uint64	nlookup;	// number of pointer lookups
 	uint64	nmalloc;	// number of mallocs
+	uint64	nfree;  // number of frees
 	
 	// Statistics about malloc heap.
 	// protected by mheap.Lock
@@ -199,7 +200,8 @@ struct MStats
 	// Statistics about garbage collector.
 	// Protected by stopping the world during GC.
 	uint64	next_gc;	// next GC (in heap_alloc time)
-	uint64	pause_ns;
+	uint64	pause_total_ns;
+	uint64	pause_ns[256];
 	uint32	numgc;
 	bool	enablegc;
 	bool	debuggc;
diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 6dcb61091d..4eace9f831 100644
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -210,6 +210,7 @@ sweepspan(MSpan *s)
 		case RefNone:
 			// Free large object.
 			mstats.alloc -= s->npages<<PageShift;
+			mstats.nfree++;
 			runtime·memclr(p, s->npages<<PageShift);
 			if(ref & RefProfiled)
 				runtime·MProf_Free(p, s->npages<<PageShift);
@@ -251,6 +252,7 @@ sweepspan(MSpan *s)
 			if(size > sizeof(uintptr))
 				((uintptr*)p)[1] = 1;	// mark as "needs to be zeroed"
 			mstats.alloc -= size;
+			mstats.nfree++;
 			mstats.by_size[s->sizeclass].nfree++;
 			runtime·MCache_Free(c, p, s->sizeclass, size);
 			break;
@@ -381,7 +383,8 @@ runtime·gc(int32 force)
 
 	t1 = runtime·nanotime();
 	mstats.numgc++;
-	mstats.pause_ns += t1 - t0;
+	mstats.pause_ns[mstats.numgc%nelem(mstats.pause_ns)] = t1 - t0;
+	mstats.pause_total_ns += t1 - t0;
 	if(mstats.debuggc)
 		runtime·printf("pause %D\n", t1-t0);
 	runtime·semrelease(&gcsema);