runtime: document MemStats.BySize fields

Change-Id: Iae8cdcd84e9b5f5d7c698abc6da3fc2af0ef839a
Reviewed-on: https://go-review.googlesource.com/34710
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

diff --git a/src/runtime/mstats.go b/src/runtime/mstats.go
index 4e111a14fe96133e4b6b292bcb12eb11d208024e..41b9005731383a8a82156e0f4338f8e2ca11a7f2 100644 (file)
--- a/src/runtime/mstats.go
+++ b/src/runtime/mstats.go
@@ -174,6 +174,7 @@ type MemStats struct {
        Lookups uint64
 
        // Mallocs is the cumulative count of heap objects allocated.
+       // The number of live objects is Mallocs - Frees.
        Mallocs uint64
 
        // Frees is the cumulative count of heap objects freed.
@@ -397,9 +398,19 @@ type MemStats struct {
        //
        // This does not report allocations larger than BySize[60].Size.
        BySize [61]struct {
-               Size    uint32
+               // Size is the maximum byte size of an object in this
+               // size class.
+               Size uint32
+
+               // Mallocs is the cumulative count of heap objects
+               // allocated in this size class. The cumulative bytes
+               // of allocation is Size*Mallocs. The number of live
+               // objects in this size class is Mallocs - Frees.
                Mallocs uint64
-               Frees   uint64
+
+               // Frees is the cumulative count of heap objects freed
+               // in this size class.
+               Frees uint64
        }
 }