[MapProxy] SV: Response time question

[Rahkonen Jukka]

Hi,

He means that if you'll take four times more pixels
(800x600=480000 vs 400x300=120000)
then you'll need approximately four times longer time.
Rather logical and to my experience pretty accurate approximation.

-Jukka Rahkonen-



Johan Sandberg wrote:
> 
> Hej!
> 
> "MapProxy should scale linear with the number of pixels. So 
> you should expect 1/4 requests when changing from 400x300 to 
> 800x600. You should measure the times with one concurrent 
> requests at first and then you should look how you can scale 
> that with increased concurrency, see below."
> 
> So do you mean that I could expect four times the time to 
> fetch an image that comes from seeded tiles when the 
> requested image size double?
> 
> Is there any good documenations on this? Would be pretty helpful!
> 
> / Johan
> 
> 
> ________________________________________
> Från: Oliver Tonnhofer [olt at omniscale.de]
> Skickat: den 31 mars 2011 17:34
> Till: Johan Sandberg
> Kopia: mapproxy at lists.osgeo.org
> Ämne: Re: Response time question
> 
> Hej Johan,
> 
> On 31.03.2011, at 15:07, Johan Sandberg wrote:
> 
> > hey!
> >
> > I'm measuring responses to Map Proxy when its seeded.
> > I dont get that satisfying response time as a wish. When I 
> perform requests of a image size of 400*300, 10 request at 
> the time I get low response time(around 50, 60ms).
> >
> > When I do image size of 800*600 the response time is up to 1-2 sec.
> > And even bigger image size give response time up to 5-6 sec.
> > Is this normal response time when requesting seeded tiles?
> 
> MapProxy should scale linear with the number of pixels. So 
> you should expect 1/4 requests when changing from 400x300 to 
> 800x600. You should measure the times with one concurrent 
> requests at first and then you should look how you can scale 
> that with increased concurrency, see below.
> 
> > The request should be alligned with the resolution that is 
> seeded so they don't have to re scaled.
> > How much is the normal cost in time of rescaling an image? 
> Do the request have to be perfectly alligned with the cached 
> resolution to achieve the low response time that I wish?
> 
> Depends on the resampling method, you have to check for your 
> self. The performance can degrade dramatically when you 
> request a lower resolution than your first/upper level, 
> because it then needs to merge lots of tiles. So make sure 
> you don't run into that.
> 
> > I have installed map proxy on a Linux computer with httpd 
> apache server. I followed the wgsi example.
> 
> You should run mod_wsgi with multiple daemon processes when 
> you have more than one CPU: 
> http://code.google.com/p/modwsgi/wiki/ConfigurationDirectives
> 
> Regards,
> Oliver
> 
> --
> Oliver Tonnhofer    | Omniscale GmbH & Co KG    | http://omniscale.de
> http://mapproxy.org | https://bitbucket.org/olt | @oltonn
> 
> 
> 
> 
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