Re: Speed up transaction completion faster after many relations are accessed in a transaction

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Speed up transaction completion faster after many relations are accessed in a transaction
Date: 2019-04-08 02:58:43
Message-ID: CAKJS1f8A2rwpYmzAtrmfC5swTL2_W-yM-UPxG5wD6H89KYkM0Q@mail.gmail.com
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On Mon, 8 Apr 2019 at 14:54, Tsunakawa, Takayuki
<tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
>
> From: 'Andres Freund' [mailto:andres(at)anarazel(dot)de]
> > Did you see that people measured slowdowns?
>
> Yeah, 0.5% decrease with pgbench -M prepared -S (select-only), which feels like a somewhat extreme test case. And that might be within noise as was mentioned.
>
> If we want to remove even the noise, we may have to think of removing the LocalLockHash completely. But it doesn't seem feasible...

It would be good to get your view on the
shrink_bloated_locallocktable_v3.patch I worked on last night. I was
unable to measure any overhead to solving the problem that way.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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