Adding new method on BucketedBytes to expose used memory (thanos-io#7137

)

* Adding new method on bucketed bytes to expose used

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>

* Removing interface, using RWMutex

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>

---------

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>

pkg/pool/pool.go

@@ -35,7 +35,7 @@ type BucketedBytes struct {
 	sizes     []int
 	maxTotal  uint64
 	usedTotal uint64
-	mtx       sync.Mutex
+	mtx       sync.RWMutex
 
 	new func(s int) *[]byte
 }
@@ -137,3 +137,10 @@ func (p *BucketedBytes) Put(b *[]byte) {
 		p.usedTotal -= uint64(sz)
 	}
 }
+
+func (p *BucketedBytes) UsedBytes() uint64 {
+	p.mtx.RLock()
+	defer p.mtx.RUnlock()
+
+	return p.usedTotal
+}