From: | Markus Wanner <markus(at)bluegap(dot)ch> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, PostgreSQL-development Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: dynamically allocating chunks from shared memory |
Date: | 2010-08-09 19:11:48 |
Message-ID: | 4C6052F4.1030607@bluegap.ch |
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Lists: | pgsql-hackers |
Hi,
On 08/09/2010 08:45 PM, Robert Haas wrote:
> Yeah, I think that's a real concern. I think we need to distinguish
> memory needs from memory wants. Ideally, we'd like our entire
> database to be cached in RAM. But that may or may not be feasible, so
> we page what we can into shared_buffers and page out as necessary to
> make room for other things. In contrast, the traditional malloc()
> approach doesn't give you much flexibility: if it returns NULL, you
> pretty much have to fail whatever operation you were trying to
> perform. For some things, that's OK. For other things, it's not.
Agreed, it's going to be a difficult compromise and it possibly is very
hard to find a good one automatically. However, I doubt our current
approach with hard limits between subsystems is the best compromise.
Regards
Markus Wanner
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