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
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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%