Re: What limits Postgres performance when the whole database lives in cache?

On Fri, Sep 2, 2016 at 10:32:46AM -0700, Andres Freund wrote:
> On 2016-09-02 11:10:35 -0600, Scott Marlowe wrote:
> > On Fri, Sep 2, 2016 at 4:49 AM, dandl <david(at)andl(dot)org> wrote:
> > > Re this talk given by Michael Stonebraker:
> > >
> > > http://slideshot.epfl.ch/play/suri_stonebraker
> > >
> > >
> > >
> > > He makes the claim that in a modern ‘big iron’ RDBMS such as Oracle, DB2, MS
> > > SQL Server, Postgres, given enough memory that the entire database lives in
> > > cache, the server will spend 96% of its memory cycles on unproductive
> > > overhead. This includes buffer management, locking, latching (thread/CPU
> > > conflicts) and recovery (including log file reads and writes).
>
> I think those numbers are overblown, and more PR than reality.
>
> But there certainly are some things that can be made more efficient if
> you don't care about durability and replication.

Agreed. Stonebraker measured Shore DBMS, which is an academic database:

http://research.cs.wisc.edu/shore/

If he had measured a production-quality database that had been optimized
like Postgres, I would take more stock of his "overhead" numbers.

--
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. +
+ Ancient Roman grave inscription +