Le jeudi 19 décembre 2013 03:08:59, Robert Haas a écrit :
> On Wed, Dec 18, 2013 at 6:07 PM, Cédric Villemain <cedric@2ndquadrant.fr>
wrote:
> >> When the prefetch process starts up, it services requests from the
> >> queue by reading the requested blocks (or block ranges). When the
> >> queue is empty, it sleeps. If it receives no requests for some period
> >> of time, it unregisters itself and exits. This is sort of a souped-up
> >> version of the hibernation facility we already have for some auxiliary
> >> processes, in that we don't just make the process sleep for a longer
> >> period of time but actually get rid of it altogether.
> >
> > I'm just a bit skeptical about the starting time: backend will ReadBuffer
> > very soon after requesting the Prefetch...
>
> Yeah, absolutely. The first backend that needs a prefetch probably
> isn't going to get it in time. I think that's OK though. Once the
> background process is started, response times will be quicker...
> although possibly still not quick enough. We'd need to benchmark this
> to determine how quickly the background process can actually service
> requests. Does anybody have a good self-contained test case that
> showcases the benefits of prefetching?
Bitmap heap fetch, I haven't a selfcase here. I didn't CC Greg but I'm sure he
has the material your asking.
--
Cédric Villemain +33 (0)6 20 30 22 52
http://2ndQuadrant.fr/
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