Super slow file saves in Gimp on Kubuntu 22.04

[Patrick Dunford]

1. Kubuntu 22.04 upgraded from 20.04
2. Gimp 2.10.30 native package.
2a. Also affects Gimp 2.99.x Beta Flatpak from Gimp Project

3. File save operations have been shown to be slower by as much as 10 times compared to the same project on Kubuntu 20.04 and same version of Gimp.
A sample project has been created with 200 layers each 4800x7200. When saved with better-but-slower XCF compression the disk file size is around 13 GiB. On the 20.04 system the save time is around 8-15 minutes. On the 22.04 system the save time can be stretched out to several hours.
A second project tested with 250 larger layers has a save time on 20.04 of just over an hour, on 22.04 it takes more than 12 hours to save.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: gimp 2.10.30-1build1
ProcVersionSignature: Ubuntu 5.15.0-27.28-generic 5.15.30
Uname: Linux 5.15.0-27-generic x86_64
ApportVersion: 2.20.11-0ubuntu82
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Wed May 4 04:06:10 2022
InstallationDate: Installed on 2022-03-27 (37 days ago)
InstallationMedia: Kubuntu 20.04.4 LTS "Focal Fossa" - Release amd64 (20220223)
ProcEnviron:
 LANGUAGE=en_NZ:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
SourcePackage: gimp
UpgradeStatus: Upgraded to jammy on 2022-04-27 (6 days ago)

[Patrick Dunford (blackwhitekez)]

During the save it was noted the process kiosslave5 was consuming around 30 GB of memory and a perentage of CPU time.
HW/SW specs:
RAM: 32 GB
Swap: 250-500 GB dedicated swap partition on M.2 SSD (2 different computers)
HDD: 2x WD Black 2 TB running in ext4 mdadm RAID-1 mirror (save location)

[Patrick Dunford (blackwhitekez)]

Gimp Flatpak Beta was also tested on debian bookworm. No save time issues were experienced on this platform.

[Patrick Dunford (blackwhitekez)]

Further test after closing all Dolphin windows yielded a more typical file save time for the 200 layer project. Additional testing to be done with the 250 layer project.
The issue with Dolphin sub processes hogging system resources will affect many other possible uses apart from Gimp file saves and should be accorded a high priority for resolution.