[gdal-dev] Changing default value for GDAL_CACHEMAX ? (was Re: Slow warping)

[Even Rouault]

Le vendredi 27 novembre 2015 13:43:34, Ari Jolma a écrit :
> 27.11.2015, 14:10, Even Rouault kirjoitti:
> > Try setting GDAL_CACHEMAX to 150 (6048 * 4032 * 3 = 73 MB. and a x 2
> > security margin)
> 
> This reduces the time into 4 s.
> 
> Quite a bit reduction from several hours.
> 
> Maybe the default is too low? 150 MB does not seem much.

Setting the default is not obvious because it depends on use cases and 
hardware configurations. What if people run 100 gdal_translate in parallel ? 
(not very common use cases admidetely, and people can still override the 
default)

Perhaps rather than a fixed value, a percentage of the total RAM would be more 
appropriate (*). Let's say 5% ? 
2 GB (which is the max for a 32 bit process) -> 100 MB
4 GB -> 200 MB
16 GB -> 800 MB.

We could also accept a GDAL_CACHEMAX=X% syntax

Even

(*) the ECW SDK does that for its own purposes, with a 25% default AFAIR

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