runtime: add per-M caches for MemStats

Avoid touching centralized state during
memory manager opreations.

R=rsc
CC=golang-dev
https://golang.org/cl/4766042

src/pkg/runtime/malloc.goc

@@ -38,18 +38,18 @@ runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
 	if(size == 0)
 		size = 1;
 
-	mstats.nmalloc++;
+	c = m->mcache;
+	c->local_nmalloc++;
 	if(size <= MaxSmallSize) {
 		// Allocate from mcache free lists.
 		sizeclass = runtime·SizeToClass(size);
 		size = runtime·class_to_size[sizeclass];
-		c = m->mcache;
 		v = runtime·MCache_Alloc(c, sizeclass, size, zeroed);
 		if(v == nil)
 			runtime·throw("out of memory");
-		mstats.alloc += size;
-		mstats.total_alloc += size;
-		mstats.by_size[sizeclass].nmalloc++;
+		c->local_alloc += size;
+		c->local_total_alloc += size;
+		c->local_by_size[sizeclass].nmalloc++;
 	} else {
 		// TODO(rsc): Report tracebacks for very large allocations.
 
@@ -61,8 +61,8 @@ runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed)
 		if(s == nil)
 			runtime·throw("out of memory");
 		size = npages<<PageShift;
-		mstats.alloc += size;
-		mstats.total_alloc += size;
+		c->local_alloc += size;
+		c->local_total_alloc += size;
 		v = (void*)(s->start << PageShift);
 
 		// setup for mark sweep
@@ -128,6 +128,7 @@ runtime·free(void *v)
 
 	// Find size class for v.
 	sizeclass = s->sizeclass;
+	c = m->mcache;
 	if(sizeclass == 0) {
 		// Large object.
 		size = s->npages<<PageShift;
@@ -139,7 +140,6 @@ runtime·free(void *v)
 		runtime·MHeap_Free(&runtime·mheap, s, 1);
 	} else {
 		// Small object.
-		c = m->mcache;
 		size = runtime·class_to_size[sizeclass];
 		if(size > sizeof(uintptr))
 			((uintptr*)v)[1] = 1;	// mark as "needs to be zeroed"
@@ -147,10 +147,10 @@ runtime·free(void *v)
 		// it might coalesce v and other blocks into a bigger span
 		// and change the bitmap further.
 		runtime·markfreed(v, size);
-		mstats.by_size[sizeclass].nfree++;
+		c->local_by_size[sizeclass].nfree++;
 		runtime·MCache_Free(c, v, sizeclass, size);
 	}
-	mstats.alloc -= size;
+	c->local_alloc -= size;
 	if(prof)
 		runtime·MProf_Free(v, size);
 	m->mallocing = 0;
@@ -163,7 +163,7 @@ runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **sp)
 	byte *p;
 	MSpan *s;
 
-	mstats.nlookup++;
+	m->mcache->local_nlookup++;
 	s = runtime·MHeap_LookupMaybe(&runtime·mheap, v);
 	if(sp)
 		*sp = s;
@@ -192,9 +192,10 @@ runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **sp)
 	}
 
 	n = runtime·class_to_size[s->sizeclass];
+	if(base) {
 		i = ((byte*)v - p)/n;
-	if(base)
 		*base = p + i*n;
+	}
 	if(size)
 		*size = n;
 
@@ -214,6 +215,29 @@ runtime·allocmcache(void)
 	return c;
 }
 
+void
+runtime·purgecachedstats(M* m)
+{
+	MCache *c;
+
+	// Protected by either heap or GC lock.
+	c = m->mcache;
+	mstats.heap_alloc += c->local_cachealloc;
+	c->local_cachealloc = 0;
+	mstats.heap_objects += c->local_objects;
+	c->local_objects = 0;
+	mstats.nmalloc += c->local_nmalloc;
+	c->local_nmalloc = 0;
+	mstats.nfree += c->local_nfree;
+	c->local_nfree = 0;
+	mstats.nlookup += c->local_nlookup;
+	c->local_nlookup = 0;
+	mstats.alloc += c->local_alloc;
+	c->local_alloc= 0;
+	mstats.total_alloc += c->local_total_alloc;
+	c->local_total_alloc= 0;
+}
+
 uintptr runtime·sizeof_C_MStats = sizeof(MStats);
 
 #define MaxArena32 (2U<<30)
@@ -361,9 +385,6 @@ func new(n uint32) (ret *uint8) {
 void*
 runtime·stackalloc(uint32 n)
 {
-	void *v;
-	uintptr sys0;
-
 	// Stackalloc must be called on scheduler stack, so that we
 	// never try to grow the stack during the code that stackalloc runs.
 	// Doing so would cause a deadlock (issue 1547).
@@ -382,11 +403,7 @@ runtime·stackalloc(uint32 n)
 			runtime·printf("stackalloc: in malloc, size=%d want %d", FixedStack, n);
 			runtime·throw("stackalloc");
 		}
-		sys0 = m->stackalloc->sys;
-		v = runtime·FixAlloc_Alloc(m->stackalloc);
-		mstats.stacks_inuse += FixedStack;
-		mstats.stacks_sys += m->stackalloc->sys - sys0;
-		return v;
+		return runtime·FixAlloc_Alloc(m->stackalloc);
 	}
 	return runtime·mallocgc(n, FlagNoProfiling|FlagNoGC, 0, 0);
 }
@@ -394,13 +411,8 @@ runtime·stackalloc(uint32 n)
 void
 runtime·stackfree(void *v, uintptr n)
 {
-	uintptr sys0;
-
 	if(m->mallocing || m->gcing || n == FixedStack) {
-		sys0 = m->stackalloc->sys;
 		runtime·FixAlloc_Free(m->stackalloc, v);
-		mstats.stacks_inuse -= FixedStack;
-		mstats.stacks_sys += m->stackalloc->sys - sys0;
 		return;
 	}
 	runtime·free(v);

src/pkg/runtime/malloc.h

@@ -185,10 +185,10 @@ void	runtime·FixAlloc_Free(FixAlloc *f, void *p);
 // Shared with Go: if you edit this structure, also edit extern.go.
 struct MStats
 {
-	// General statistics.  No locking; approximate.
+	// General statistics.
 	uint64	alloc;		// bytes allocated and still in use
 	uint64	total_alloc;	// bytes allocated (even if freed)
-	uint64	sys;		// bytes obtained from system (should be sum of xxx_sys below)
+	uint64	sys;		// bytes obtained from system (should be sum of xxx_sys below, no locking, approximate)
 	uint64	nlookup;	// number of pointer lookups
 	uint64	nmalloc;	// number of mallocs
 	uint64	nfree;  // number of frees
@@ -221,7 +221,6 @@ struct MStats
 	bool	debuggc;
 	
 	// Statistics about allocation size classes.
-	// No locking; approximate.
 	struct {
 		uint32 size;
 		uint64 nmalloc;
@@ -267,9 +266,20 @@ struct MCache
 {
 	MCacheList list[NumSizeClasses];
 	uint64 size;
-	int64 local_alloc;	// bytes allocated (or freed) since last lock of heap
-	int64 local_objects;	// objects allocated (or freed) since last lock of heap
+	int64 local_cachealloc;	// bytes allocated (or freed) from cache since last lock of heap
+	int64 local_objects;	// objects allocated (or freed) from cache since last lock of heap
+	int64 local_alloc;	// bytes allocated and still in use since last lock of heap
+	int64 local_total_alloc;	// bytes allocated (even if freed) since last lock of heap
+	int64 local_nmalloc;	// number of mallocs since last lock of heap
+	int64 local_nfree;	// number of frees since last lock of heap
+	int64 local_nlookup;	// number of pointer lookups since last lock of heap
 	int32 next_sample;	// trigger heap sample after allocating this many bytes
+	// Statistics about allocation size classes since last lock of heap
+	struct {
+		int64 nmalloc;
+		int64 nfree;
+	} local_by_size[NumSizeClasses];
+	
 };
 
 void*	runtime·MCache_Alloc(MCache *c, int32 sizeclass, uintptr size, int32 zeroed);
@@ -378,6 +388,7 @@ void	runtime·markspan(void *v, uintptr size, uintptr n, bool leftover);
 void	runtime·unmarkspan(void *v, uintptr size);
 bool	runtime·blockspecial(void*);
 void	runtime·setblockspecial(void*);
+void	runtime·purgecachedstats(M*);
 
 enum
 {

src/pkg/runtime/mcache.c

@@ -48,7 +48,7 @@ runtime·MCache_Alloc(MCache *c, int32 sizeclass, uintptr size, int32 zeroed)
 			v->next = nil;
 		}
 	}
-	c->local_alloc += size;
+	c->local_cachealloc += size;
 	c->local_objects++;
 	return v;
 }
@@ -90,7 +90,7 @@ runtime·MCache_Free(MCache *c, void *v, int32 sizeclass, uintptr size)
 	l->list = p;
 	l->nlist++;
 	c->size += size;
-	c->local_alloc -= size;
+	c->local_cachealloc -= size;
 	c->local_objects--;
 
 	if(l->nlist >= MaxMCacheListLen) {

src/pkg/runtime/mgc0.c

@@ -484,6 +484,7 @@ sweep(void)
 			// Mark freed; restore block boundary bit.
 			*bitp = (*bitp & ~(bitMask<<shift)) | (bitBlockBoundary<<shift);
 
+			c = m->mcache;
 			if(s->sizeclass == 0) {
 				// Free large span.
 				runtime·unmarkspan(p, 1<<PageShift);
@@ -491,14 +492,13 @@ sweep(void)
 				runtime·MHeap_Free(&runtime·mheap, s, 1);
 			} else {
 				// Free small object.
-				c = m->mcache;
 				if(size > sizeof(uintptr))
 					((uintptr*)p)[1] = 1;	// mark as "needs to be zeroed"
-				mstats.by_size[s->sizeclass].nfree++;
+				c->local_by_size[s->sizeclass].nfree++;
 				runtime·MCache_Free(c, p, s->sizeclass, size);
 			}
-			mstats.alloc -= size;
-			mstats.nfree++;
+			c->local_alloc -= size;
+			c->local_nfree++;
 		}
 	}
 }
@@ -533,14 +533,26 @@ cachestats(void)
 {
 	M *m;
 	MCache *c;
+	int32 i;
+	uint64 stacks_inuse;
+	uint64 stacks_sys;
 
+	stacks_inuse = 0;
+	stacks_sys = 0;
 	for(m=runtime·allm; m; m=m->alllink) {
+		runtime·purgecachedstats(m);
+		stacks_inuse += m->stackalloc->inuse;
+		stacks_sys += m->stackalloc->sys;
 		c = m->mcache;
-		mstats.heap_alloc += c->local_alloc;
-		c->local_alloc = 0;
-		mstats.heap_objects += c->local_objects;
-		c->local_objects = 0;
+		for(i=0; i<nelem(c->local_by_size); i++) {
+			mstats.by_size[i].nmalloc += c->local_by_size[i].nmalloc;
+			c->local_by_size[i].nmalloc = 0;
+			mstats.by_size[i].nfree += c->local_by_size[i].nfree;
+			c->local_by_size[i].nfree = 0;
 		}
+	}
+	mstats.stacks_inuse = stacks_inuse;
+	mstats.stacks_sys = stacks_sys;
 }
 
 void
@@ -603,6 +615,7 @@ runtime·gc(int32 force)
 	sweep();
 	t2 = runtime·nanotime();
 	stealcache();
+	cachestats();
 
 	mstats.next_gc = mstats.heap_alloc+mstats.heap_alloc*gcpercent/100;
 	m->gcing = 0;

src/pkg/runtime/mheap.c

@@ -57,10 +57,7 @@ runtime·MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, int32 acct)
 	MSpan *s;
 
 	runtime·lock(h);
-	mstats.heap_alloc += m->mcache->local_alloc;
-	m->mcache->local_alloc = 0;
-	mstats.heap_objects += m->mcache->local_objects;
-	m->mcache->local_objects = 0;
+	runtime·purgecachedstats(m);
 	s = MHeap_AllocLocked(h, npage, sizeclass);
 	if(s != nil) {
 		mstats.heap_inuse += npage<<PageShift;
@@ -258,10 +255,7 @@ void
 runtime·MHeap_Free(MHeap *h, MSpan *s, int32 acct)
 {
 	runtime·lock(h);
-	mstats.heap_alloc += m->mcache->local_alloc;
-	m->mcache->local_alloc = 0;
-	mstats.heap_objects += m->mcache->local_objects;
-	m->mcache->local_objects = 0;
+	runtime·purgecachedstats(m);
 	mstats.heap_inuse -= s->npages<<PageShift;
 	if(acct) {
 		mstats.heap_alloc -= s->npages<<PageShift;

test/mallocrep.go

@@ -47,6 +47,7 @@ func main() {
 			b := runtime.Alloc(uintptr(j))
 			during := runtime.MemStats.Alloc
 			runtime.Free(b)
+			runtime.GC()
 			if a := runtime.MemStats.Alloc; a != 0 {
 				println("allocated ", j, ": wrong stats: during=", during, " after=", a, " (want 0)")
 				panic("fail")

test/mallocrep1.go

@@ -60,6 +60,7 @@ func AllocAndFree(size, count int) {
 		fmt.Printf("size=%d count=%d stats=%+v\n", size, count, *stats)
 	}
 	n3 := stats.Alloc
+	runtime.GC()
 	for j := 0; j < count; j++ {
 		i := j
 		if *reverse {
@@ -72,6 +73,7 @@ func AllocAndFree(size, count int) {
 			panic("fail")
 		}
 		runtime.Free(b[i])
+		runtime.GC()
 		if stats.Alloc != uint64(alloc-n) {
 			println("free alloc got", stats.Alloc, "expected", alloc-n, "after free of", n)
 			panic("fail")