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Re: Uh, I change my mind about commit_delay + commit_siblings (sort of)

From: Peter Geoghegan <peter(at)2ndquadrant(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, tgl(at)sss(dot)pgh(dot)pa(dot)us
Subject: Re: Uh, I change my mind about commit_delay + commit_siblings (sort of)
Date: 2012-06-28 18:38:35
Message-ID: CAEYLb_XO8_fhspZ31eK5xC53i6y-gLsoFESsbRqZHTojBO_f-w@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 28 June 2012 19:25, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Peter Geoghegan <peter(at)2ndquadrant(dot)com> wrote:
>
>> Is anyone aware of a non-zero commit_delay in the wild today? I
>> personally am not.
>
> http://archives.postgresql.org/pgsql-performance/2011-11/msg00083.php

In that thread, Robert goes on to say to the OP that has set commit_delay:

>On Fri, Nov 4, 2011 at 2:45 PM, Claudio Freire <klaussfreire(at)gmail(dot)com> wrote:
>> I don't think 1 second can be such a big difference for the bgwriter,
>> but I might be wrong.
>
> Well, the default value is 200 ms.   And I've never before heard of
> anyone tuning it up, except maybe to save on power consumption on a
> system with very low utilization.  Nearly always you want to reduce
> it.
>
>> The wal_writer makes me doubt, though. If logged activity was higher
>> than 8MB/s, then that setting would block it all.
>> I guess I really should lower it.
>
> Here again, you've set it to ten times the default value.  That
> doesn't seem like a good idea.  I would start with the default and
> tune down.

So, let me rephrase my question: Is anyone aware of a non-zero
commit_delay in the wild today with sensible reasoning behind it?

-- 
Peter Geoghegan       http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services

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