low nginx performance

Hi,
I met with a problem:
The throughput performance(Connections Per Sec) of Nginx with ssl_engine qat is lower than that without.
At the server end, I used command ./nginx to start nginx. And I changed the worker_processes in nginx.conf every time(from 1 to 8).
At the client end, I used command openssl s_time ip:port -new -nbio -time 20 -cipher AES128-SHA1 to test the connections / user sec.

Here is the result:
avg-without-qat: 4287 3836 3884 3902 3939 3624 3617 3218
avg-with-qat: 3478 3101 3202 3221 2902 2855 3014 1769
worker_processes from 1 to 8
I found that of every worker_processes the cps of nginx with qat is lower than that without.
This result is different from that on the white paper: QAT&OpenSSL performance
I could not find out why .

conf
I read the README.md on github.com/intel/QAT_Engine and github.com/intel/asynch_mode_nginx carefully. I set some parameters in the configuration file accordingly and here it is.
nginx.conf:
worker_processes 8;
worker_cpu_affinity auto;
ssl_asynch on;
load_module modules/ngx_ssl_engine_qat_module.so;
ssl_engine {
use_engine qat;
default_algorithms ALL;
qat_engine {
qat_offload_mode async;
qat_notify_mode poll;
qat_poll_mode internal;
qat_internal_poll_interval 10000;
}
}
dh895xcc_dev0.conf:
[SHIM]
NumberCyInstances = 1
NumberDcInstances = 0
NumProcesses = 32
LImitDevAccess = 1
Crypto
Cy0Name = “UserCY0”
Cy0InPolled = 1
Cy0CoreAffinity = 0