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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