Re: Time to up bgwriter_lru_maxpages?

From: Andres Freund <andres(at)anarazel(dot)de>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Time to up bgwriter_lru_maxpages?
Date: 2017-02-02 19:52:39
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On 2017-02-02 14:47:53 -0500, Robert Haas wrote:
> I expect that increasing the maximum value of shared_buffers beyond
> what can be stored by an integer could have a noticeable distributed
> performance cost for the entire system. It might be a pretty small
> cost, but then again maybe not; for example, BufferDesc's buf_id
> member would have to get wider, and probably the freeNext member, too.
> Andres already did unspeakable things to make a BufferDesc fit into
> one cache line for performance reasons, so that wouldn't be great
> news.

Yea, we'd have to get rid of BufferDesc's buf_id - but that's not that
hard, just a bit verbose. You can get the buf_id already with a tiny bit
of pointer math. I don't think there should be too many other changes,
but I might be wrong.


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