Re: Vacuum: allow usage of more than 1GB of work mem

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Claudio Freire <klaussfreire(at)gmail(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Vacuum: allow usage of more than 1GB of work mem
Date: 2017-01-20 21:25:18
Message-ID: 20170120212518.f62v2bwfw22hex7f@alvherre.pgsql
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You posted two patches with this preamble:

Claudio Freire wrote:

> Attached is the raw output of the test, the script used to create it,
> and just in case the patch set used. I believe it's the same as the
> last one I posted, just rebased.

There was no discussion whatsoever of the "prefetch" patch in this
thread; and as far as I can see, nobody even mentioned such an idea in
the thread. This prefetch patch appeared out of the blue and there was
no discussion about it that I can see. Now I was about to push it after
some minor tweaks, and went to search where was its justification, only
to see that there was none. Did anybody run tests with this patch?

I attach it now one more time. My version is based on the latest
Claudio posted at
I don't know if there are differences to the version first posted.
I only changed the magic number 32 to a #define, and added a
CHECK_FOR_INTERRUPTS in the prefetching loop.

FWIW, I think this patch is completely separate from the maint_work_mem
patch and should have had its own thread and its own commitfest entry.
I intend to get a look at the other patch next week, after pushing this

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachment Content-Type Size
0001-Prefetch-blocks-during-lazy-vacuum-s-truncation-scan.patch text/plain 2.8 KB

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