lib/workingsetcache: switch from split cache to full cache after the cache size exceeds 95% of split capacity

Previously the switch occurred when the cache size becomes 100% of its capacity. The cache size could never reach 100% capacity.
This could prevent from switching from the split cache to full cache, thus reducing the cache effectiveness.

lib/workingsetcache/cache.go

@@ -153,7 +153,7 @@ func (c *Cache) cacheSizeWatcher() {
 		var cs fastcache.Stats
 		curr := c.curr.Load().(*fastcache.Cache)
 		curr.UpdateStats(&cs)
-		if cs.BytesSize >= uint64(c.maxBytes)/2 {
+		if cs.BytesSize >= uint64(0.95*float64(c.maxBytes)/2) {
 			break
 		}
 	}