message: fix: performance degraded when disable prefetch
  Use perf to profile nydusd, we can see _blake3_hash_many_sse41 take max
  percent of total cpu cycles. It seems that we calculate digest for each
  io, which is not expected.
diff: @@ -242,6 +242,7 @@ impl BlobCache {
  .is_ok()
  {
  self.metrics.whole_hits.inc();
  + cache_entry.set_ready();
  trace!(
  "recover blob cache {} {} reuse {} offset {} size {}",
  chunk.block_id(),
  