[Qgis-user] Qgis crashes while loading WMTS layers

[Patrick Dunford]

Sorry I don't know enough about virtual memory implementation to comment.

The only software I am sufficiently familiar with from experience is 
Gimp, which has the setting where you can specify the size of the tile 
cache. So for example I have a tile cache set to 200 GB. It starts with 
physical RAM then pushes into the swap space.

I can monitor the resource use of the system with a widget displayed on 
the panel on the computer. This shows CPU use, memory and swap space 
use. From there I can watch the resource use of the system while doing 
things. I can compare the resource usage being displayed for the system 
with the Gimp dashboard.

The assumption for me is that the operating system, in theory, presents 
a virtual memory model to applications, whereby the actual physical 
implementation is abstracted, such that when an application makes a 
request for more memory allocated, it is essentially transparent where 
the information is actually physically stored. Maybe that is not accurate?

On 27/01/20 8:18 pm, Bo Victor Thomsen wrote:
>
> Hi Patrick -
>
> Swap space is an internal component the underlying operating system 
> (OS) uses for handling memory request that exceeds the ram resources 
> of the computer. A normal user program like QGIS has no "knowledge" 
> about this facility and can't directly manipulate the swap system.
>
> As Jonathan describes, "swap" space for for other program is temporary 
> file storage, usually placed in a specific directory (in windows 
> designated by the environment variable %TEMP%). QGIS uses this 
> directory too.
>
> A QGIS crash can be caused by running out of memory resources and/or 
> temp file storage. However, that is result of a bad setup of your 
> operating system, which can limit how much swap space, that can be 
> allocated to memory hungry programs and the size of hard-disk used for 
> swap space and/or temp storage
>
> So what to do:
>
>  1. Check memory consumption when using QGIS. Is it really using all
>     the ram - memory and starting to swap ?
>  2. Check the setup of the swap space parameters. It it using a
>     hard-disk which is running out of storage space.
>  3. Check the setup of the temp storage parameters. It it using a
>     hard-disk which  is running out of storage space ? Are the user
>     allowed to allocate enough storage?
>
> (I can't be more specific not knowing the operating system you use)
>
> If the above checks out OK and you still have issues with QGIS crashing..
>
> The shift from QGIS 2.x to QGIS 3.x meant a complete change of the 
> underlying graphics subsystem QT from ver 4.x to ver. 5.x (and a huge 
> amount of other changes).
>
> One or more of those changes  might cause a failure as you described. 
> However, you have to check the above and then write an error issue 
> (https://github.com/qgis/QGIS/issues) where you describe error 
> messages, your specific setup like operating system and version, QGIS 
> version and - if possible - test-data and project to replicate the issue.
>
> -- 
> Med venlig hilsen / Kind regards
>
> Bo Victor Thomsen
>
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