"./examples/streaming_decompression" considerably slower than "zstd -d"

**Describe the bug**
The `streaming_decompression` tool in the `examples` folder is consistently slower than `zstd -d`, I wonder what could be the cause?

I tried to link `streaming_compression` statically and dynamically, no difference there.

**Expected behavior**
The run time is supposed to be comparable, but `streaming_decompression` is consistently slower, about 20% slower than `zstd -d` on a Centos 7 machine.

```
zstd155 --no-check < data > data.zst

sudo sh -c "/bin/echo 3 > /proc/sys/vm/drop_caches"
time -p zstd155 -d < data.zst > data1

sudo sh -c "/bin/echo 3 > /proc/sys/vm/drop_caches"
time -p ./zstd155/examples/streaming_decompression data.zst > data2
```