pg.ddx.io pgsql-admin@postgresql.org mailing list archive help / color / mirror / Atom feed From: Cédric Villemain <cedric.villemain.debian@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Greg Stark <gsstark@mit.edu>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: Florian Helmberger <fh@25th-floor.com>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum
Date: Mon, 30 May 2011 01:32:54 +0200
Message-ID: <BANLkTinL6QuAm_Xf8teRZboG2Mdy3dR_vw@mail.gmail.com> (raw )
In-Reply-To: <19876.1306680027@sss.pgh.pa.us >
References: <4DD28F73.6010108@25th-floor.com >
<25017.1306291669@sss.pgh.pa.us >
<4DDCA801.70805@25th-floor.com >
<19738.1306338472@sss.pgh.pa.us >
<BANLkTi=973Arh-nXLO6YFP7_ZTCeNp-X7w@mail.gmail.com >
<22497.1306341699@sss.pgh.pa.us >
<BANLkTi=jcKSU5zR+JG2BvfLNCtezC9sb+g@mail.gmail.com >
<15043.1306423500@sss.pgh.pa.us >
<BANLkTikrCaoZCVrda6SNCUQFiYvvZX75BA@mail.gmail.com >
<25097.1306426982@sss.pgh.pa.us >
<BANLkTikxM6V5DUsXnDEs84z=oRMbyeoOgA@mail.gmail.com >
<4DDE475B020000250003DD63@gw.wicourts.gov >
<BANLkTikTbZ8gibj+X++vkdqkxxJCU6trWw@mail.gmail.com >
<4DDE5033020000250003DD71@gw.wicourts.gov >
<BANLkTikGu30z1rwYeN0NwuO8jMFWHzus+Q@mail.gmail.com >
<4DDE7EB8020000250003DDA8@gw.wicourts.gov >
<9007.1306446600@sss.pgh.pa.us >
<BANLkTinREie2cX2zqZPSEfUsZsdM+GjymQ@mail.gmail.com >
<28116.1306609295@sss.pgh.pa.us >
<BANLkTi=6RYvEVfKn8ufPEf9meGVEu=fHsQ@mail.gmail.com >
<11295.1306645848@sss.pgh.pa.us >
<BANLkTimbSiUZC7+ZZJOzMWp=M2jYZZcJSg@mail.gmail.com >
<19876.1306680027@sss.pgh.pa.us >
2011/5/29 Tom Lane <tgl@sss.pgh.pa.us>:
> =?ISO-8859-1?Q?C=E9dric_Villemain?= <cedric.villemain.debian@gmail.com> writes:
>> 2011/5/29 Tom Lane <tgl@sss.pgh.pa.us>:
>>> OK, do you like the attached version of that logic? (Other fragments
>>> of the patch as before.)
>
>> The idea was that remove only one page from the VACUUM will prevent
>> relfrozenxid update and reltuples (and relpages) update.
>> Now, I beleive that once we've skip at least one page thanks to
>> SKIP_PAGES_THRESHOLD, then we should be more agressive and remove as
>> many as possible pages from the VACUUM, tks to the VM.
>
> That would require proof, not just suggestion. Skipping pages will
> defeat the OS read-ahead algorithm, and so could easily cost more than
> reading them.
Correct, it needs proof. Parenthesis: I did learn also that reading
the first block of a file make read-ahead have its larger window from
the beginning (the one that posix_fadvise_sequential set too), so
remove those initial reads might be counter-productive also. But this
is damn hard to benchmark because the read ahead is also influenced by
memory pressure for example.
view thread (48+ messages)
Message-ID: <BANLkTinL6QuAm_Xf8teRZboG2Mdy3dR_vw@mail.gmail.com>
Permalink: ../BANLkTinL6QuAm_Xf8teRZboG2Mdy3dR_vw@mail.gmail.com/
Also on: postgresql.org/message-id/BANLkTinL6QuAm_Xf8teRZboG2Mdy3dR_vw@mail.gmail.com
copy link · copy postgr.es
reply Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: cedric.villemain.debian@gmail.com, tgl@sss.pgh.pa.us, gsstark@mit.edu, robertmhaas@gmail.com, Kevin.Grittner@wicourts.gov, fh@25th-floor.com, alvherre@commandprompt.com, pgsql-hackers@postgresql.org
Subject: Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum
In-Reply-To: <BANLkTinL6QuAm_Xf8teRZboG2Mdy3dR_vw@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox