| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| 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 15:40:13 |
| Message-ID: | 20160105154013.GD31334@momjian.us |
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| Lists: | pgsql-hackers |
On Tue, Jan 5, 2016 at 04:31:15PM +0100, Andres Freund wrote:
> On 2016-01-05 10:28:25 -0500, Bruce Momjian wrote:
> > 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?
>
> Yes? But it's ok sizewise on the common platforms?
What is the uncommon part? I guess I missed that.
--
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. +
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