Fwd: Process scheduling in postgres

I have a 4 core CPU for postgres and I have submitted 6 queries parallely in 6 different sessions. But I am seeing only 1 query per CPU and the remainig queries are queued. I am not sure why is it happening. Do you have any special scheduler for postgres? I can see that CPU has been shared with other non postgres processes but postgres processes are not sharing any CPU within a core. The following is the process states.

lms       2868  2209 98 07:20 ?        00:02:30 postgres: lms controller [local] SELECT
lms       2869  2209 98 07:20 ?        00:02:30 postgres: lms controller [local] SELECT
lms       2870  2209  0 07:20 ?        00:00:00 postgres: lms controller [local] SELECT
lms       2871  2209  0 07:20 ?        00:00:00 postgres: lms controller [local] SELECT
lms       2872  2209  0 07:20 ?        00:00:00 postgres: lms controller [local] SELECT
lms       2873  2209 98 07:20 ?        00:02:30 postgres: lms controller [local] SELECT

If you see above, three Select queries have been queued. They are acquiring CPU only when there is a core without any postgres query running on it.