From: | Bruce Momjian <bruce(at)momjian(dot)us> |
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To: | "andres(at)anarazel(dot)de" <andres(at)anarazel(dot)de> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Ildus Kurbangaliev <i(dot)kurbangaliev(at)postgrespro(dot)ru>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
Subject: | Re: [PATCH] Refactoring of LWLock tranches |
Date: | 2016-01-05 15:28:25 |
Message-ID: | 20160105152825.GC31334@momjian.us |
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Lists: | pgsql-hackers |
On Sun, Dec 13, 2015 at 12:35:34PM +0100, Andres Freund wrote:
> > > One thing to call out is that an "oversized" s_lock can now make
> > > BufferDesc exceed 64 bytes, right now that's just the case when it's
> > > larger than 4 bytes. I'm not sure if that's cause for real concern,
> > > given that it's not very concurrent or ancient platforms where that's
> > > the case.
> > > http://archives.postgresql.org/message-id/20150915020625.GI9666%40alap3.anarazel.de
> > > would alleviate that concern again, as it collapses flags, usage_count,
> > > buf_hdr_lock and refcount into one 32 bit int...
> >
> > I don't think that would be worth worrying about even if we didn't
> > have a plan in mind that would make it go away again, and even less so
> > given that we do have such a plan.
>
> Ok cool. I'm not particularly concerned either, just didn't want to slip
> that in without having it called out.
Uh, didn't you and I work in 9.5 to make sure the BufferDesc was 64-byte
aligned to avoid double-CPU cache invalidation that was causing
performance problems on a server you were testing?
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
+ Roman grave inscription +
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