the bandwidth is low between my gpus. tested with p2pBandwidthLatencyTest

i have 4 1080ti on my machine. the nvidia driver version is 384.111.
compared to others’ test(usually close to 10 GB/s), the bandwidth seems very low on my machine. Did i miss something? thanks

below is my test result:

GPU0	GPU1	GPU2	GPU3	CPU Affinity

GPU0 X PHB PHB PHB 0-7
GPU1 PHB X PHB PHB 0-7
GPU2 PHB PHB X PHB 0-7
GPU3 PHB PHB PHB X 0-7

Unidirectional P2P=Disabled Bandwidth Matrix (GB/s)
D\D 0 1 2 3
0 61.23 3.12 1.64 1.64
1 2.95 361.02 1.64 1.64
2 1.52 1.52 61.29 1.50
3 1.55 1.55 1.53 61.26
Unidirectional P2P=Enabled Bandwidth Matrix (GB/s)
D\D 0 1 2 3
0 61.33 3.26 2.37 2.02
1 3.06 360.76 2.93 3.06
2 3.05 3.05 245.83 3.06
3 2.73 2.73 2.73 385.23
Bidirectional P2P=Disabled Bandwidth Matrix (GB/s)
D\D 0 1 2 3
0 391.80 5.41 5.36 5.10
1 5.42 363.31 5.21 5.08
2 5.40 5.25 392.16 5.07
3 5.10 5.08 5.08 390.23
Bidirectional P2P=Enabled Bandwidth Matrix (GB/s)
D\D 0 1 2 3
0 393.55 6.11 6.11 5.44
1 6.08 363.88 6.13 5.45
2 6.08 6.10 392.20 5.46
3 5.42 5.43 5.44 389.48
P2P=Disabled Latency Matrix (us)
D\D 0 1 2 3
0 2.17 10.42 10.43 12.07
1 10.43 2.18 10.36 11.80
2 10.40 10.35 2.15 11.74
3 12.28 11.78 11.97 2.16
P2P=Enabled Latency Matrix (us)
D\D 0 1 2 3
0 2.18 4.78 4.76 5.53
1 4.63 2.20 4.58 5.35
2 4.75 4.77 2.20 5.53
3 6.70 6.74 6.74 2.17