preview in dolphin is slow with many pictures

[Peter Penz]

Hi Mathias,

Thanks a lot for your very detailed performance analyzes, they are very, very 
helpful!

One thing that comes into my mind is that Dolphin for KDE 4.1 creates image 
borders around the previews. For this Dolphin has to resize the images first 
and afterwards draws a shadow around it.

I'll do some tests how much performance this costs...

Best regards,
Peter

On Thursday, 12. June 2008 23:46:03 Mathias Kraus wrote:
[...]
> Ok, I had to investigate this issue a bit more, so I did a few tests.
>
> system:
> kubuntu 8.04
> qt4.4 from riddels repository
>
> dolphin3 -> 0.9.2
> dolphin4 -> 1.0.99 ; build from today
> thunar -> 0.9
>
> I didn't took nautilus, because it had more dependencies than thunar and as
> far as I know, nautius and the gnome file open dialog have much in common
> and the file open dialog is extremly slow with many files.
>
> here my tests:
>
> I removed the information panel for all tests.
>
> open ~/.thumbnails/normal with ~5000 files; file size is a few KiB; preview
> off; app fresh started
> dolphin3: 1...2 seconds; fast scrolling -> fastest
> dolphin4: ~3 seconds; fast scrolling
> thunar: ~3 seconds, slightly faster than dolphin4, but somethimes more than
> 5 seconds; fast scrolling
>
> open ~/.thumbnails/normal with ~5000 files; file size is a few KiB; preview
> off; entering folder the second time
> dolphin3: ~1 second; fast scrolling
> dolphin4: ~2 seconds; fast scrolling
> thunar: <1 second; fast scrolling -> fastest
>
> open ~/.thumbnails/normal with ~5000 files; file size is a few KiB; preview
> on; app fresh started; ~/.thumbnails deleted before entering
> dolphin3: 1...2 seconds; fast scrolling; very fast preview generation ->
> fastest
> dolphin4: ~10 seconds; almost impossible
> thunar: ~3 seconds; fast scrolling
>
> open folder with ~1300 files; file size is a few MiB; preview on; app fresh
> started; ~/.thumbnails deleted before entering folder
> dolphin3: almost instantanously; fast scrolling; fast preview generation,
> slightly faster than thunar
> dolphin4: slightly faster than the other two; fast scrolling but GUI is
> from time to time noticeably blocked; much slower than the other two in
> preview generation
> thunar: slightly faster than dolphin3; fast scrolling; fast preview
> generation
>
> tried dolphin4 with about 400 files from ~/.thumbnails/normal and
> surprisingly scrolling was slower than in the folder with the ~1300 big
> files
>
> coclusion:
> with preview off, no information panel and big files, dolphin4 feels the
> fastest from the tree, but with preview on it becomes the slowest,
> especially with many small files, while there is no difference with the
> other two.
>
> during the test I discovered another bug. dolphin doesn't stop generating
> previews when a folder is opened and then switching off preview. you can
> reproduce it if you open ~/.thumbnails/normal in splitview and delete the
> content, then open a folder with images in the second one and switch
> preview on and then immediatelly off. there are still new thumbnails that
> appear and it stops only after closing the view.
>
> furthermore, while files are added to a folder, dolphing becomes also
> somethimes slow, e.g. open ~/.thumbnails/normal and a second folder with
> images and preview on, so that new files appear in the thumbnail folder.
> scrolling in the thumbnail folder is now somethimes really slow.
>
> deleting many (>500) small files also blocks the GUI.
>
> I also noticed that preview generation thakes much less CPU in dolphin3
> than in dolphin4, while it is also faster.
>
> some suggestions for preview:
> -start from top left, instead from bottom right, if easy doable
> -start with images that are completely in the visible area, not only
> partly, but I think this will be more expensive
>
> Hope it helps,
> Mathias
>
> > Best regards,
> > Peter
> >
> > > #!/bin/bash
> > >
> > > for((jahr=2000; jahr<=2008; jahr++))
> > > do
> > > 	for((monat=1; monat<=9; monat++))
> > > 	do
> > > 		for((tag=1; tag<=9; tag++))
> > > 		do
> > > 			wget http://www.sinfest.net/comikaze/comics/$jahr-0$monat-0$tag.gif
> > > 		done
> > > 		for((tag=10; tag<=31; tag++))
> > > 		do
> > > 			wget http://www.sinfest.net/comikaze/comics/$jahr-0$monat-$tag.gif
> > > 		done
> > > 	done
> > > 	for((monat=10; monat<=12; monat++))
> > > 	do
> > > 		for((tag=1; tag<=9; tag++))
> > > 		do
> > > 			wget http://www.sinfest.net/comikaze/comics/$jahr-$monat-0$tag.gif
> > > 		done
> > > 		for((tag=10; tag<=31; tag++))
> > > 		do
> > > 			wget http://www.sinfest.net/comikaze/comics/$jahr-$monat-$tag.gif
> > > 		done
> > > 	done
> > > done
> > >
> > >
> > > Thanks, I really appreciate your effort.
> > >
> > > > Thanks!
> > > > Peter
> > > >
> > > > > In opposite to Gwenview Dolphin tries to create previews for each
> > > > > MIME-type.
> > > >
> > > >[...]