Re: PrivateRefCount (for 8.3)

Hi,

What is the opinion of the list as to the best way of measuring if the
following implementation is ok?

http://archives.postgresql.org/pgsql-hackers/2007-01/msg00752.php

As mentioned in earlier mails, this will reduce the per-backend usage of
memory by an amount which will be a fraction (single digit percentage)
of (NBuffers
* int) size. I have done pgbench/dbt2 runs and I do not see any negative
impact because of this. Are there any other suggestions for measuring the
backend memory footprint?

Regards,
Nikhils

On 2/21/07, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
>
> Added to TODO:
>
> * Consider decreasing the amount of memory used by PrivateRefCount
>
> http://archives.postgresql.org/pgsql-hackers/2006-11/msg00797.php
> http://archives.postgresql.org/pgsql-hackers/2007-01/msg00752.php
>
>
>
> ---------------------------------------------------------------------------
>
> Simon Riggs wrote:
> > On Mon, 2006-11-27 at 14:42 -0500, Bruce Momjian wrote:
> > > Simon Riggs wrote:
> > > > int8 still seems like overkjll. When will the ref counts go above 2
> on a
> > > > regular basis? Surely refcount=2 is just chance at the best of
> times.
> > > >
> > > > Refcount -> 2 bits per value, plus a simple overflow list? That
> would
> > > > allow 0,1,2 ref counts plus 3 means look in hashtable to find real
> > > > refcount.
> > >
> > > At two bits, would we run into contention for the byte by multiple
> > > backends?
> >
> > No contention, its a private per-backend data structure. That's why we
> > want to reduce the size of it so badly.
> >
> > --
> > Simon Riggs
> > EnterpriseDB http://www.enterprisedb.com
> >
> >
> >
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> --
> Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
> EnterpriseDB http://www.enterprisedb.com
>
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>
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