Re: Proposal for CSN based snapshots - Mailing list pgsql-hackers

From Andres Freund
Subject Re: Proposal for CSN based snapshots
Date
Msg-id 20160822174734.kziqfc3i4gix2g7b@alap3.anarazel.de
Whole thread Raw
In response to Re: Proposal for CSN based snapshots  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On 2016-08-22 13:41:57 -0400, Robert Haas wrote:
> On Mon, Aug 22, 2016 at 1:32 PM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
> >> But what about the best case?  If we create a scenario where there are
> >> no open read-write transactions at all and (somehow) lots and lots of
> >> ProcArrayLock contention, how much does this help?
> >
> > I ran some quick pgbench tests on my laptop, but didn't see any meaningful
> > benefit. I think the best I could see is about 5% speedup, when running
> > "pgbench -S", with 900 idle connections sitting in the background. On the
> > positive side, I didn't see much slowdown either. (Sorry, I didn't record
> > the details of those tests, as I was testing many different options and I
> > didn't see a clear difference either way.)
> 
> That's not very exciting.

I think it's neither exciting nor worrying - the benefit of the pgproc
batch clearing itself wasn't apparent on small hardware either...



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