@Override
        public String toString() {
            StringBuilder sb = new StringBuilder("ByteBufAllocMetric{allocatorMetric=");
            sb.append(metric);
            sb.append(", allocatedMemory=");
            sb.append(allocatedMemory);
            sb.append(", detail=");
            for (Map.Entry<String, Long> entry : detail.entrySet()) {
                sb.append(entry.getKey()).append("=").append(entry.getValue()).append(", ");
            }
            sb.append("pooled=");
            sb.append(policy.isPooled());
            sb.append(", direct=");
            sb.append(policy.isDirect());
            sb.append("}");
            return sb.toString();
        }
Get the chunk size of the allocator.
It returns {@link Optional#empty} if the {@link #policy} is not {@link ByteBufAllocPolicy#isPooled}.
s3stream/src/main/java/com/automq/stream/s3/ByteBufAlloc.java