http – Nginx v1.15.9 slow loading speed with HTTP2 enabled

I noticed that the loading speed started a little slower after enabling HTTP v2 in Nginx v1.15.9.

To enable HTTP v2 support that I just added http2 to listen out directive:

listen to 443 ssl http2;

Average load time of a single 5MB file:
– HTTP v2: 31s
– HTTP v1.1: 18s

I played a little http2_recv_buffer_size but no result

It does not look like the expected behavior. Are there any suggestions to review?