From: | William Yu <wyu(at)talisys(dot)com> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Low Performance for big hospital server .. |
Date: | 2005-01-03 19:57:50 |
Message-ID: | crc87h$2ehh$1@news.hub.org |
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Thread: | |
Lists: | pgsql-performance |
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.
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