Re: WIP parallel restore patch

Okay, I have had a chance to run some timing benchmarks.
Here are my results for the parallel pg_restore patch:

Ken
--------------------------------------------------
Server settings:
  max_connections = 100                   # (change requires restart)  shared_buffers = 256MB                    # min
128kB work_mem = 128MB                                # min 64kB  maintenance_work_mem = 256MB            # min 1MB
 
  fsync = on # turns forced synchronization on or off
  synchronous_commit = off                # immediate fsync at commit
  full_page_writes = on # recover from partial page writes  checkpoint_segments = 10 # in logfile segments, min 1, 16MB
each autovacuum = on # Enable autovacuum subprocess? 'on'
 

The total final database size is 6.5GB. Here are the timings for
the different run parallelism from 1 to 8 on a 4-core AMD box:

-bash-3.00$ time pg_restore -U postgres -p 5435 -d rttest /tmp/rtout.pz
...

real    19m3.175s
user    1m2.968s
sys     0m8.202s

improvement - 0%

-bash-3.00$ time pg_restore -U postgres -p 5435 -m 2 -d rttest /tmp/rtout.pz
...
real    12m55.680s
user    1m12.440s
sys     0m8.343s

improvement - 32%

-bash-3.00$ time pg_restore -U postgres -p 5435 -m 4 -d rttest /tmp/rtout.pz
...
real    9m45.056s
user    1m1.892s
sys     0m8.980s

improvement - 49%

The system only has 4 cores, but here are the results with "-m 8":

-bash-3.00$ time pg_restore -U postgres -p 5435 -m 8 -d rttest /tmp/rtout.pz
...
real    8m15.320s
user    0m55.206s
sys     0m8.678s

improvement - 53%