Re: Performance Bottleneck

Martin Foster wrote:

> Gaetano Mendola wrote:
>
>>
>>
>> Let start from your postgres configuration:
>>
>> shared_buffers = 8192    <==== This is really too small for your
>> configuration
>> sort_mem = 2048
>>
>> wal_buffers = 128    <==== This is really too small for your
>> configuration
>>
>> effective_cache_size = 16000
>>
>> change this values in:
>>
>> shared_buffers = 50000
>> sort_mem = 16084
>>
>> wal_buffers = 1500
>>
>> effective_cache_size = 32000
>>
>>
>> to bump up the shm usage you have to configure your OS in order to be
>> allowed to use that ammount of SHM.
>>
>> This are the numbers that I feel good for your HW, the second step now is
>> analyze your queries
>>
>
> These changes have yielded some visible improvements, with load averages
> rarely going over the anything noticeable.   However, I do have a
> question on the matter, why do these values seem to be far higher then
> what a frequently pointed to document would indicate as necessary?
>
> http://www.varlena.com/GeneralBits/Tidbits/perf.html
>
> I am simply curious, as this clearly shows that my understanding of
> PostgreSQL is clearly lacking when it comes to tweaking for the hardware.

Unfortunately there is no a "wizard tuning" for postgres so each one of
us have a own "school". The data I gave you are oversized to be sure
to achieve improvements. Now you can start to decrease these values
( starting from the wal_buffers ) in order to find the good compromise
with your HW.




Regards
Gaetano Mendola