| 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 |
| Message-ID: | 20170202195239.cvraezzap6jtuxuf@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
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.
Andres
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