Re: CLUSTER, reform_and_rewrite_tuple(), and parallelism

From: Andres Freund <andres(at)anarazel(dot)de>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: CLUSTER, reform_and_rewrite_tuple(), and parallelism
Date: 2016-08-18 00:20:06
Message-ID: 20160818002006.s7wko4pq3vurozaw@alap3.anarazel.de
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On 2016-08-17 21:17:56 -0300, Alvaro Herrera wrote:
> Peter Geoghegan wrote:
>
> > This doesn't seem that interesting, but not sure what you're looking for.
> >
> > I also attach cycles flamegraph.
>
> I may be blind, but what are those write() calls attributed to
> heap_form_tuple?

libc isn't compiled with -fno-omit-frame-pointer (and even if, it uses
assembly without setup of the frame pointer), so frame pointer based
call graphs are wrong through libc. The attributions are based on
random stuff in the frame pointer at that point. You either need to use
dwarf or lbr to get accurate ones.

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