Re: Low Performance for big hospital server ..

Dave Cramer wrote:

>
>
> William Yu wrote:
>
>> amrit(at)health2(dot)moph(dot)go(dot)th wrote:
>>
>>> I will try to reduce shared buffer to 1536 [1.87 Mb].
>>
>>
>>
>> 1536 is probaby too low. I've tested a bunch of different settings on
>> my 8GB Opteron server and 10K seems to be the best setting.
>
>
> Be careful here, he is not using opterons which can access physical
> memory above 4G efficiently. Also he only has 4G the 6-10% rule still
> applies

10% of 4GB is 400MB. 10K buffers is 80MB. Easily less than the 6-10% rule.

>> To figure out your effective cache size, run top and add free+cached.
>
>
> My understanding is that effective cache is the sum of shared buffers,
> plus kernel buffers, not sure what free + cached gives you?

Not true. Effective cache size is the free memory available that the OS
can use for caching for Postgres. In a system that runs nothing but
Postgres, it's free + cached.