[gdal-dev] RFC 47 and Threading

[Blake Thompson]

Jeff,

Thanks Blake for the detailed response. I did not realize that I did not do
> a reply all in my previous email I sent.
>

Not an issue, glad you guys are interested in my changes.

>
> --> I thought that this was not possible using current trunk GDAL because
> of the global cache. At least the writing side using multiple threads can
> cause issues.
> See this response on a older topic I found in GDAL dev list:
> http://lists.osgeo.org/pipermail/gdal-dev/2013-January/035215.html
> The response there was for a similar question as the one i posted about
> supporting of batch translating of dataset with this RFC .
>

I do believe it is possible in the current trunk of GDAL (and I have
written some code to do it with out seeing any issues). There is a "lock"
on raster blocks currently that prevents them from being removed from the
cache if they are currently be utilized.


>
> --> Ok, I was under the wrong impression that in addition of  a cache per
> dataset there is still a cap of global cache that oversee the total cache
> used by GDAL.
>

This really isn't possible, because if something needs to be removed from
the cache and there is nothing to remove from the current dataset, it would
have to go to another dataset to lower the cache size. At this point the
per dataset cache really has limited meaning, because a lot of the same
issues will occur.

--> Is this mean that in addition of the per dataset cache once can still
> use the global cache (only not per dataset one) and have the scenario of
> translating multiple datasets in a parallel way
> works ok (without threading issues due to current implementation global
> cache).
>

Yes, it will work to translate multiple datasets in a parallel way with a
global cache.

Thanks,

Blake
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