Date: Wed, 23 Mar 2016 21:43:41 +0100
From: Andres Freund <andres@anarazel.de>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: David Steele <david@pgmasters.net>, Robert Haas <robertmhaas@gmail.com>,
	Thom Brown <thom@linux.com>, Simon Riggs <simon@2ndquadrant.com>,
	Jesper Pedersen <jesper.pedersen@redhat.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Speed up Clog Access by increasing CLOG buffers
Message-ID: <20160323204341.GB4686@awork2.anarazel.de>
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On 2016-03-23 12:33:22 +0530, Amit Kapila wrote:
> On Wed, Mar 23, 2016 at 12:26 PM, Amit Kapila <amit.kapila16@gmail.com>
> wrote:
> >
> > On Tue, Mar 22, 2016 at 4:22 PM, Andres Freund <andres@anarazel.de> wrote:
> > >
> > >
> > > I think it's worthwhile to create a benchmark that does something like
> > > BEGIN;SELECT ... FOR UPDATE; SELECT pg_sleep(random_time);
> > > INSERT;COMMIT; you'd find that if random is a bit larger (say 20-200ms,
> > > completely realistic values for network RTT + application computation),
> > > the success rate of group updates shrinks noticeably.
> > >
> >
> > Will do some tests based on above test and share results.
> >
> 
> Forgot to mention that the effect of patch is better visible with unlogged
> tables, so will do the test with those and request you to use same if you
> yourself is also planning to perform some tests.

I'm playing around with SELECT txid_current(); right now - that should
be about the most specific load for setting clog bits.

Andres


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