Bug 457906

Summary:	krusader is very slow with 7-zip 7zip 7z archives
Product:	[Applications] krusader	Reporter:	empyreal <empyreal>
Component:	krarc	Assignee:	Krusader Bugs Distribution List <krusader-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	krusader-bugs-null, voidpointertonull+bugskdeorg
Priority:	NOR
Version First Reported In:	Git
Target Milestone:	---
Platform:	Kubuntu
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description empyreal 2022-08-15 09:40:36 UTC

SUMMARY
Archived home folder into 4.5 GB 7z. Browsing through archive is very slow. Need to wait 1 minute to move into folder.  Extracting is a disaster.  Tried on NTFS and ext4.

STEPS TO REPRODUCE
1. Create 7z archive from home folder, for example.
2. Browse 7z archive and move to /home/user/snap/
3. Ctrl + C firefox folder (in my case 400 MB).
4. Move to desired location and Ctrl + V

OBSERVED RESULT
1500 files (110 MB) are extracted from 7z for 30 minutes. Very slow work. Total Commander on Windows 10 makes such operations very fast without any discomfort. Why is that? I use zip instead of 7zip because of this problem.

EXPECTED RESULT
Expect to browse and extract 7z in a blink of an eye (=

Operating System: Kubuntu 22.10
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.4
Kernel Version: 5.15.0-46-generic (64-bit)
Graphics Platform: X11
Processors: 12 × AMD Ryzen 5 1600 Six-Core Processor
Memory: 15,6 GiB of RAM

Comment 1 empyreal 2022-08-15 10:57:07 UTC

Forgot one thing: right-click and Extract archive here works fast. It's often easier to Extract here than browse archives and extract separate folders.

Comment 2 Pedro V 2024-04-29 10:05:41 UTC

Already dug into the issue somewhat in Bug #422142 , but I'll partially reiterate what's there with more focus on Krusader.

Aside from the K7zip implementation not looking like it's suitable for fast browsing, I'm not even sure if that's being used, and if it is, then that means that the file list is processed multiple times.

Apparently there's a sneaky `bool check7zEncrypted = true` default option for checking archives because someone figured that `// encryption check is expensive, check only if it's necessary`, but it doesn't look like this is ever avoided.
The price comes from running the external 7z executable to get a full list of files with details included. I also had the suspicion that this keeps on being done when moving around within the archive, and running `KDE_FORK_SLAVES=true krusader -d` shows output that suggests it may be the case, but I haven't seen enough to be confident.

While 7z handling doesn't seem to be great overall in KDE, Krusader seems to be special with its own odd problems added.