Hi Patrick,
I can't comment on the core issue, but just a point for clarification -
I thought Swap memory usage was something the operating system dealt
with? Isn't it usually transparent to the application?
A quick search indicates that what GIMP calls swap is really a bespoke
folder for GIMP to store temporary files (in a fashion similar to
virtual memory/swap) rather than the system swap file; FME does this too
(they call it a "temporary directory").
I can certainly see why that would have value - it looks like QGIS has
one, at least for temporary outputs -
https://github.com/qgis/QGIS/issues/28222 - but whether it's as well
used as it should be I leave for others to comment on (I have no idea
what it's used for).
Cheers,
Jonathan
On 2020-01-26 12:19, Patrick Dunford wrote:
Good day to all.
Not so long ago I wrote a post about issues handling large numbers of
raster files. This results from what appears to be an architectural
design limitation of Qgis in that it only has enough resources
available for a certain (unknown) number of raster layers and does not
have any effective system for dealing with the exhaustion of these
resources.
I also noted that the software does not appear to have the ability to
use the swap (virtual memory) resources within a system to deal with
the apparent exhaustion of resources, as other software would. For
example, Gimp which I use for graphical editing is able to handle
certain projects using a swap space of 200 GB, which consists of 32 GB
of physical RAM and the rest in SSD. It is not unusual with some of
these graphics projects to have 100 GB or more of swap space in use,
without crashing the system. (This being possible since Gimp 2.10 with
its ability to write files of more than 4 GB)
Whilst it is possible to manage the number of layers with file based
rasters, this cannot be done with a WMTS server because there is no
way I am aware of to manage the number of layers that can be
downloaded from the server.
Version 2.18 and earlier almost never crashed with excess layers,
usually all that would happen is a layer would be displayed with
invalid data. However, crashes have become the norm with 3.x versions
of software.
It seems to me there is a big architectural problem in the software
with its inability to utilise the full resources of the system in
order to process the number of layers that a WMTS server is capable of
issuing.
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