Search time increased comparing with 0.10.2 using index: SQ8H

[del-zhenwu]

Please state your issue using the following template and, most importantly, in English.

Describe the bug
0.10.2:

17:19:29  │  Nq/Top-k   │      1      │     10      │     100     │    1000     │
17:19:29  ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤
17:19:29  │           1 │        0.04 │        0.02 │        0.03 │        0.03 │
17:19:29  │          10 │        0.06 │        0.06 │        0.07 │        0.07 │
17:19:29  │         100 │        0.15 │        0.15 │        0.16 │         0.2 │
17:19:29  │         200 │        0.26 │        0.26 │        0.28 │        0.42 │
17:19:29  │         500 │        0.58 │        0.58 │        0.64 │        0.88 │
17:19:29  │        1000 │        1.15 │        1.14 │        1.21 │        1.81 │

0.10.3:

16:50:40  │  Nq/Top-k   │      1      │     10      │     100     │    1000     │
16:50:40  ├─────────────┼─────────────┼─────────────┼─────────────┼─────────────┤
16:50:40  │           1 │        0.03 │        0.03 │        0.04 │        0.04 │
16:50:40  │          10 │         0.1 │         0.1 │        0.09 │        0.09 │
16:50:40  │         100 │        0.76 │        0.79 │        0.79 │        0.85 │
16:50:40  │         200 │        1.52 │        1.47 │        1.51 │        1.65 │
16:50:40  │         500 │        3.72 │         3.7 │        3.73 │        4.04 │
16:50:40  │        1000 │        7.34 │        7.23 │        7.38 │        7.98 │

Steps/Code to reproduce behavior
dataset:

sift_50m_2048_128_l2_sq8h

params:

gpu_threshold:
  2000
index params:
  type: sq8h:
  nlist : 16384
search params:
  nrpobe: 32

log path:

/test/milvus/db_data_8/sift_50m_2048_128_l2_sq8h

Expected behavior
A clear and concise description of what you expected to happen.

Method of installation

• Docker/cpu
• Docker/gpu
• Build from source

Environment details

• Hardware/Softwars conditions (OS, CPU, GPU, Memory)

• Milvus version (master or released version)

Configuration file
Settings you made in server_config.yaml or milvus.yaml

paste-file-content-here

Screenshots
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Additional context
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