how to improve the performance of creating index

Hi, all

         I am trying to improve the performance of creating index.

         I’ve set shared_buffers = 1024MB

                   Effective_cache_size = 1024MB

                   Work_mem = 1GB

                   Maintenance_work_mem=512MB

         (I’m sure that the server process has received the SIGHUP signal)

However, when create index, I found that the memory used by Postgres is only 50MB. And it is very slow. How to make it faster?

All helps are appreciated.

Thanks.

Yinan