Re: Time to up bgwriter_lru_maxpages?

David Steele <david@pgmasters.net>

From: David Steele <david@pgmasters.net>
To: Robert Haas <robertmhaas@gmail.com>, Jim Nasby <Jim.Nasby@bluetreble.com>
Cc: Andres Freund <andres@anarazel.de>, Michael Paquier <michael.paquier@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, "Joshua D. Drake" <jd@commandprompt.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2017-03-16T16:39:20Z
Lists: pgsql-hackers
On 2/2/17 2:47 PM, Robert Haas wrote:
> On Wed, Feb 1, 2017 at 9:47 PM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
>> Before doing that the first thing to look at would be why the limit is
>> currently INT_MAX / 2 instead of INT_MAX.
> 
> Generally the rationale for GUCs with limits of that sort is that
> there is or might be code someplace that multiplies the value by 2 and
> expects the result not to overflow.
> 
> 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.
> 
> Anyway, I committed the patch posted here.  Or the important line out
> of the two, anyway.  :-)

It seems that this submission should be marked as "Committed" with
Robert as the committer.  Am I missing something?

-- 
-David
david@pgmasters.net


Commits

  1. Increase upper bound for bgwriter_lru_maxpages.