Re: Handing off SLRU fsyncs to the checkpointer

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Jakub Wartak <Jakub(dot)Wartak(at)tomtom(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Handing off SLRU fsyncs to the checkpointer
Date: 2020-08-26 18:09:50
Message-ID: 20200826180950.GA16713@alvherre.pgsql
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On 2020-Aug-25, Andres Freund wrote:

> Hi,
>
> On 2020-08-26 15:58:14 +1200, Thomas Munro wrote:
> > > --12.51%--compactify_tuples
> > > PageRepairFragmentation
> > > heap2_redo
> > > StartupXLOG
> >
> > I wonder if there is something higher level that could be done to
> > reduce the amount of compaction work required in the first place, but
> > in the meantime I'm very happy if we can improve the situation so much
> > with such a microscopic improvement that might eventually benefit
> > other sorting stuff...
>
> Another approach could be to not perform any sorting during recovery,
> instead including enough information in the WAL record to avoid doing a
> full blown PageRepairFragmentation during recovery.

Hmm, including the sorted ItemId array in the WAL record might make
sense to alleviate the qsort work ...

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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