Question about using async jobs and qat_sw.

I've been testing qat_sw performance using `openssl speed` test and I've noticed using async_jobs option makes a big speed-up difference. However there are some doubts I hope someone can help me to understand when using -async_jobs.

Here is the command I've been used:

`openssl speed -engine qatengine -async_jobs n rsa2048`

Questions:
1. I see no big performance difference when using -async_jobs as 10, 100 or 1000.
a. Is there a 'sweet' point for the the async_jobs value parameter?
b. How to find the best performant async_jobs number?
c. How the -async_jobs value affects the performance?

2. If I use `-async_jobs 7` (or less) as value parameter the performance is very poor even when compared to a test not using async_jobs, i.e `openssl speed rsa2048`.
a. Is that an issue or an expected behavior considering the low -async-jobs number and due to the overhead to process jobs asynchronously?

Some number just as an example:

`openssl speed rsa2048` gives me:

Doing 2048 bits private rsa's for 10s: 10487 2048 bits private RSA's in 10.00s
Doing 2048 bits public rsa's for 10s: 351725 2048 bits public RSA's in 10.00s
...
sign verify sign/s verify/s
rsa 2048 bits 0.000954s 0.000028s 1048.7 35172.5

`openssl speed -engine qatengine -async_jobs 1 rsa2048` gives me:

Doing 2048 bits private rsa's for 10s: 893 2048 bits private RSA's in 1.03s
Doing 2048 bits public rsa's for 10s: 985 2048 bits public RSA's in 0.11s
...
sign verify sign/s verify/s
rsa 2048 bits 0.001153s 0.000112s 867.0 8954.5

Thanks in advance for any clarification.