[Gdal-dev] Will increasing the RAM on a server increase the speed of gdalwarp?

[John Mitchell]

Frank,

Thanks for the recommendation of adding --config GDAL_CACHEMAX 500 -wm 500
to the gdalwarp command.

With --config GDAL_CACHEMAX 500 -wm 500 added to gdalwarp the speed of
mosaicing 6 tiles creating a mosaic of 3 gb on a server with 4 gb of RAM
increased the gdalwarp speed by 25%.

I then tried --config GDAL_CACHEMAX 625 -wm 625 instead of --config
GDAL_CACHEMAX 500 -wm 500 and I got the following error:
Out of memory allocatint 400042260 byte destination buffer

If the RAM was increased beyond 4 GB then I would be able to increase to
GDAL_CACHEMAX 625 -wm 625 and beyond, but you don't believe that above 500
will have any effect on gdalwarp performance.  Correct?

Thanks,

John Mitchell

On 7/13/07, Frank Warmerdam <warmerdam at pobox.com> wrote:
>
> John Mitchell wrote:
> > Hi,
> >
> > Will increasing the RAM on a server increase the speed of gdalwarp?
> >
> > If I have a server that currently has 4 gigs of RAM and I increase the
> > RAM to say 75 gigs will I notice a difference in the speed of processing
> > a 75 gig image via gdalwarp?
>
> John,
>
> What commandline options are you using with gdalwarp?  By default
> gdalwarp won't take much advantage of your 4GB of existing RAM.
>
> You might want to try setting the -wm flag. For example "-wm 500" will
> operate on 500MB chunks at a time which is better than the default.
> Increasing the io block cache size may also help.  This can be done
> on the command like:
>
> gdalwarp --config GDAL_CACHEMAX 500 -wm 500 ...
>
> This uses 500MB of RAM for read/write caching, and 500MB of RAM for
> working buffers during the warp.  Beyond that I'm doubtful more
> memory will make a substantial difference.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, http://osgeo.org
>
>


-- 
John J. Mitchell
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