Re: Speed up Clog Access by increasing CLOG buffers

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: David Steele <david(at)pgmasters(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Speed up Clog Access by increasing CLOG buffers
Date: 2016-03-22 14:36:13
Message-ID: CAA4eK1K9Z5L8rBu6nAk55oSTE4iC_aw=d+MyqpEy4UL6=aTG8w@mail.gmail.com
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On Tue, Mar 22, 2016 at 6:29 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2016-03-22 18:19:48 +0530, Amit Kapila wrote:
> > > I'm actually rather unconvinced that it's all that common that all
> > > subtransactions are on one page. If you have concurrency - otherwise
> > > there'd be not much point in this patch - they'll usually be heavily
> > > interleaved, no? You can argue that you don't care about subxacts,
> > > because they're more often used in less concurrent scenarios, but if
> > > that's the argument, it should actually be made.
> > >
> >
> > Note, that we are doing it only when a transaction has less than equal
to
> > 64 sub transactions.
>
> So?
>

They should fall on one page, unless they are heavily interleaved as
pointed by you. I think either subtransactions are present or not, this
patch won't help for bigger transactions.

I will address your other review comments and send an updated patch.

Thanks for the review.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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