On 3 September 2015 at 07:24, Peter Geoghegan <p...@heroku.com> wrote:
> On Wed, Sep 2, 2015 at 7:12 AM, Andres Freund <and...@anarazel.de> wrote: > > What worries me about adding explicit prefetching is that it's *highly* > > platform and even micro-architecture dependent. Why is looking three > > elements ahead the right value? > > Because that was the fastest value following testing on my laptop. You > are absolutely right to point out that this isn't a good reason to go > with the patch -- I share your concern. All I can say in defense of > that is that other major system software does the same, without any > regard for the underlying microarchitecture AFAICT. So, yes, > certainly, more testing is required across a reasonable cross-section > of platforms to justify the patch. > FWIW someone else found 3 to be good on the platform they tested on: http://www.naftaliharris.com/blog/2x-speedup-with-one-line-of-code/ Peter, would you be able to share the test case which you saw the speedup on. So far I've been unable to see much of an improvement. Regards David Rowley -- David Rowley http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Training & Services
