Re: strange performance regression between 7.4 and 8.1

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

--
Jeff Frost, Owner <jeff(at)frostconsultingllc(dot)com>
Frost Consulting, LLC http://www.frostconsultingllc.com/
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