| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Andres Freund <andres(at)2ndquadrant(dot)com>, Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, Markus Wanner <markus(at)bluegap(dot)ch>, Ants Aasma <ants(at)cybertec(dot)at>, Bruce Momjian <bruce(at)momjian(dot)us>, obartunov <obartunov(at)postgrespro(dot)ru>, Teodor Sigaev <teodor(at)postgrespro(dot)ru>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Subject: | Re: Proposal for CSN based snapshots |
| Date: | 2016-08-22 17:47:34 |
| Message-ID: | 20160822174734.kziqfc3i4gix2g7b@alap3.anarazel.de |
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| Lists: | 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(at)iki(dot)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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