the speed of forward, caffe with cudnn slower than without cudnn?

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test model: Alexnet, Vgg16, Resnet50, Restnet101, CUDA version: cuda-9.0, CUDNN version: cudnn7.6 Operating system: v100, 1080ti

use caffe time to test speed ./build/tools/caffe time --model alexnet.prototxt --weights alexnet.caffemodel --gpu 1

I use two modes: with cudnn and without cudnn;

when batch = 1: with cudnn is slower than without cudnn, for example,

resnet101: forward use time: with cudnn : 34ms without cudnn: 18ms

when batch = 10: with cudnn is quicker than with cudnn, for example

resnet101:

forward us time: with cudnn: 60ms without cudnn: 48ms

so my question is why batch=1, with cudnn is slower? how do cudnn for conv speed up?

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v100

batch = 1

with cudnn

without cudnn

![Uploading IMG_20210918_154127.jpg…]()

batch = 10

with cudnn

without cudnn