Re: Adding skip scan (including MDAM style range skip scan) to nbtree

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: Tomas Vondra <tomas(at)vondra(dot)me>
Cc: Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>
Subject: Re: Adding skip scan (including MDAM style range skip scan) to nbtree
Date: 2025-05-09 14:17:39
Message-ID: CAH2-Wz=XfWkSJ7+HU938j6Hfg2EXie4Sw0VvMPu_TQnxkQgSFg@mail.gmail.com
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On Fri, May 9, 2025 at 8:58 AM Tomas Vondra <tomas(at)vondra(dot)me> wrote:
> I'm also not sure about the root cause, but while investigating it one
> of the experiments I tried was tweaking the glibc malloc by setting
>
> export MALLOC_TOP_PAD_=$((64*1024*1024))
>
> which keeps a 64MB "buffer" in glibc, to reduce the amount of malloc
> syscalls. And with that, the results change to this:

You're sure that the problem is an increase in the number of
malloc()s? If that's what this is, then it shouldn't be too hard to
debug.

--
Peter Geoghegan

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