Poor performance in single-buffer test

We test run single hash jobs on one core:

- ISA-L
```c
*_ctx_mgr_init(mgr_);
*_ctx_mgr_submit(mgr_, &ctxpool_, buf, text_length, HASH_ENTIRE);
*_ctx_mgr_flush(mgr_);
```

- OpenSSL
```c
*_Init(&ctx_);
*_Update(&ctx_, buf, text_length);
*_Final(digest_, &ctx_);
```

OpenSSL is better than ISA-L(same result in update test):

| Library | Algorithm | 100B(us) | 1KB(us) | 256KB(us) | 512KB(us) | 1MB(us) |
| ------- | --------- | -------- | -------- | ----------- | ----------- | ----------- |
| OpenSSL | MD5 | 0.259577 | 1.973022 | 466.580400 | 930.553100 | 1858.246400 |
| ISA-L | MD5 | 0.510208 | 3.434382 | 788.836000 | 1580.523900 | 3185.874900 |
| | | | | | | |
| OpenSSL | SHA1 | 0.243943 | 1.435872 | 329.519600 | 654.810200 | 1309.367800 |
| ISA-L | SHA1 | 0.326654 | 1.885040 | 393.532000 | 786.502300 | 1573.971600 |
| | | | | | | |
| OpenSSL | SHA256 | 0.432444 | 3.031160 | 714.659800 | 1429.176200 | 2858.618900 |
| ISA-L | SHA256 | 0.597858 | 4.251419 | 997.934900 | 1993.451800 | 3989.759000 |
| | | | | | | |
| OpenSSL | SHA512 | 0.337439 | 2.207246 | 477.429400 | 953.789300 | 1908.231500 |
| ISA-L | SHA512 | 0.598538 | 4.924967 | 1119.788800 | 2237.286500 | 4411.418500 |

If the test is wrong, please look through my steps above and tell me what I am doing wrong.
If not, please tell me why this result.
Thanks