Re: strange performance regression between 7.4 and 8.1

On 3/1/07, Jeff Frost <jeff(at)frostconsultingllc(dot)com> wrote:
> On Thu, 1 Mar 2007, Alex Deucher wrote:
>
> >> Vacuum? Analayze? default_statistics_target? How many shared_buffers?
> >> effective_cache_size? work_mem?
> >>
> >
> > I'm running the autovacuum process on the 8.1 server. vacuuming on
> > the old server was done manually.
> >
> > default_statistics_target and effective_cache_size are set to the the
> > defaults on both.
> >
> > postgres 7.4 server:
> > # - Memory -
> > shared_buffers = 82000 # 1000 min 16, at least
> > max_connections*2, 8KB each
> > sort_mem = 8000 # 1024 min 64, size in KB
> > vacuum_mem = 32000 # 8192 min 1024, size in KB
> > # - Free Space Map -
> > #max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each
> > #max_fsm_relations = 1000 # min 100, ~50 bytes each
> > # - Kernel Resource Usage -
> > #max_files_per_process = 1000 # min 25
> >
> > postgres 8.1 server:
> > # - Memory -
> > shared_buffers = 100000 # min 16 or max_connections*2, 8KB
> > each
> > temp_buffers = 2000 #1000 # min 100, 8KB each
> > max_prepared_transactions = 100 #5 # can be 0 or more
> > # note: increasing max_prepared_transactions costs ~600 bytes of shared
> > memory
> > # per transaction slot, plus lock space (see max_locks_per_transaction).
> > work_mem = 10000 #1024 # min 64, size in KB
> > maintenance_work_mem = 524288 #16384 # min 1024, size in KB
> > #max_stack_depth = 2048 # min 100, size in KB
> >
> > I've also tried using the same settings from the old server on the new
> > one; same performance issues.
> >
>
> If this is a linux system, could you give us the output of the 'free' command?

total used free shared buffers cached
Mem: 8059852 8042868 16984 0 228 7888648
-/+ buffers/cache: 153992 7905860
Swap: 15631224 2164 15629060

> Postgresql might be choosing a bad plan because your effective_cache_size is
> way off (it's the default now right?). Also, what was the block read/write

yes it's set to the default.

> speed of the SAN from your bonnie tests? Probably want to tune
> random_page_cost as well if it's also at the default.
>

------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
luna12-san 16000M 58896 91 62931 9 35870 5 54869 82 145504 13 397.7 0

effective_cache_size is the default.

Alex