Re: Increase default effective_cache_size?

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Teodor Sigaev <teodor(at)sigaev(dot)ru>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org, Russ Brown <pickscrape(at)gmail(dot)com>
Subject: Re: Increase default effective_cache_size?
Date: 2006-09-25 12:17:01
Message-ID: 4517C8BD.2080908@dunslane.net
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Teodor Sigaev wrote:
>> current default of 1000 pages (8Mb) seems really pretty silly for modern
>> machines; we could certainly set it to 10 times that without problems,
>> and maybe much more. Thoughts?
>
> May be, set by default effective_cache_size equal to number of shared
> buffers?
> If pgsql is configured to use quarter or half of total memory for
> shared buffer, then effective_cache_size will have good approximation...
>
>

Initdb does not currently make any attempt to discover the extent of
physical or virtual memory, it simply tries to start postgres with
certain shared_buffer settings, starting at 4000, and going down until
we get a success.

max_fsm_pages is now fixed proportionally with shared_buffers, and I
guess we could do something similar with effective_cache_size, but since
IIRC this doesn't involve shared memory I'm inclined to agree with Tom
that it should just be fixed at some substantially higher level.

cheers

andrew

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