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My QGIS startup time and response time (after minimizing/switching tasks) is significantly delayed, only when I am connected to the internet. As soon as I disconnect from Internet, all loading becomes almost instanteneous.

E.g. I start QGIS, it loads for minutes, but when I disconnect, it loads immediately. Or: I minimize QGIS and after a few minutes try to use it again, but get only a blank screen, loading for minutes until it shows all UI. But when I disconnect from internet, it is back and responsive immediately.

My insights so far:

  • Debugging/Development Tools show, that the "Main Window" is responsible for startup delay e.g. 500 seconds or more (and probably also the unresponsive behavior). But I don't know how to drill down what exactly in the "Main Window" is causing the lag (see image below).

  • This was reproducible with QGIS LTR 3.28.11 and still is after the recent upgrade to QGIS LTR 3.34.4.

  • Switching to a clean/new user profile (without plugins and so on) has no effect (besides the reduced plugin load time, but the long delay isn't caused by that)

  • I am aware of network drives that can be the source of slowdown. In fact they were at some point for me, since we have company network drives P: / U:. These cause long lags and unresponsive behavior when not in VPN with fast internet (in Windows generally, and also in QGIS with all browser/load file based operations), but I could fix that for QGIS by removing P: and U: from searchable drives (by modifying the .ini). Also that doesn't seem to be the reason here, since the long load times remain even if in a fast VPN environment (that has access to internet).

  • I generally find QGIS a bit sluggish when it comes to loading network layers. I think the network requests shouldn't slow down the main UI, but should run asynchronous to all other tasks, leaving a responsive UI despite of e.g. WMS/WMTS layers being loaded or not... in an attempt to achieve faster response times I lowered the timeout for network requests, however that is always a trade-off between long load times with unresponsive behavior and dropping network requests up to the extent that nothing is loaded at all for slow connections Timeout for Network Request setting

  • I also read through these threads, without finding anything that helps: What can be a reason of QGIS slow work? and How to fix QGIS being extremely slow?

Does anyone else experience similar problems? Any suggestions on what else to try?

Main Window

Honeybear
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  • you can try sysinternals procmon or fiddler to see what resource is being requested. – JGH Mar 01 '24 at 19:53
  • What kind of datasets are you accessing over the internet by vpn? I found that file geodatabase layers were problematic in both ArcGIS and QGIS, so I only used local versions of them. Shapefiles worked much better. – John Mar 02 '24 at 13:24
  • @John: During the described behavior I am not accessing anything via VPN (simply starting the locally installed QGIS without a project and/or opening a local project). – Honeybear Mar 03 '24 at 07:39
  • @JGH: thanks for the suggestion, I tried procmon right now and filtered for Process Name qgis. I get a lot (as in thousands) of entries with many details, any additional hints what I am looking for exactly? Operations mostly revolve around RegQueryKey and Query/Read/Close File/Directory; Results are mostly SUCCESS, with a few REPARSE/NAME NOT FOUND/BUFFER OVERFLOW here and there. But I don't have a conclusive lead rightaway (as in specific network paths that time out or URLs being requested...) – Honeybear Mar 03 '24 at 07:50

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