From: Simon Riggs <simon@2ndQuadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Hot Standby on git
Date: Mon, 05 Oct 2009 19:49:49 +0100
Message-ID: <1254768589.4691.249.camel@ebony.2ndQuadrant> (raw)
In-Reply-To: <6950.1254752345@sss.pgh.pa.us>
References: <1253958559.4449.833.camel@ebony.2ndQuadrant>
<4ABF4522.6060601@enterprisedb.com>
<1254743455.4691.153.camel@ebony.2ndQuadrant>
<6950.1254752345@sss.pgh.pa.us>
On Mon, 2009-10-05 at 10:19 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndQuadrant.com> writes:
> > I don't see how that helps at all. The objective of lock counters was to
> > know if we can skip acquiring an LWlock on all lock partitions. This
> > change keeps the lock counters yet acquires the locks we were trying to
> > avoid. This change needs some justification since it is not a bug fix.
>
> [ scratches head ... ] Why is hot standby messing with this sort of
> thing at all? It sounds like a performance optimization that should
> be considered separately, and *later*.
Possibly.
We have 3 suggested approaches:
* Avoid taking LockPartition locks while we get info for Hot Standby
during normal running, by means of a ref counting scheme (Simon)
* Take the locks and implement a ref counting scheme (Heikki)
* Take the locks, worry later (Tom)
The middle ground seems pointless to me.
I'm happy to go with simple lock-everything-for-now but it's pretty
clear its going to be a annoying performance hit. If we do that we
should put in a parameter to turn on/off so that those who will never
use Hot Standby can avoid this completely.
I'll wait for Heikki's thoughts before implementing anything.
--
Simon Riggs www.2ndQuadrant.com
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To: pgsql-hackers@postgresql.org
Cc: simon@2ndQuadrant.com, tgl@sss.pgh.pa.us, heikki.linnakangas@enterprisedb.com
Subject: Re: Hot Standby on git
In-Reply-To: <1254768589.4691.249.camel@ebony.2ndQuadrant>
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