Public bug reported:
Binary package hint: dolphin
Using Dolphin Version 1.3
Using KDE 4.3.2
when viewing a folder with many large images in dolphin using thumbnail
mode it uses so much ram that the system becomes completely unresponsive
as everything else is moved to swap. (this happened on a machine with
4GB of physical ram) the way i see it this boils down to 2 problems:
1) it uses more ram than a single image takes up in decompressed form. i
guess this is because it's using multitasking to speed up the
calculations on multicore cpu's which is good, but apparently it doesn't
take ram requirements into account when deciding how many images to
process at a time. the images were 8kx8k with 32 bits per color so each
should take up only 256mb. i know these are large images but not *that*
uncommon.
2) dolphin makes the decision whether to calculate a thumbnail based on
the image's filesize when it should also consider the dimensions. in
some cases huge images are very compressible and end up having very
small filesizes.
3) the algorithms used seem not to optimized for memory usage. when
using weighed average scaling for example there is no need to store the
full sized image in memory. just an array of the size of the thumbnail
image (with a few more bits per channel) should be enough. this is
probably hard to do though as it requires working with the low level
functions of several image libraries.
ways to reproduce:
fill a folder with lots of high resolution images and simply open it in
dolphin and enable thumbnail mode. 16kx16k png images filled with a single
color should definitely work as they will have a small file size but huge
dimensions.
** Affects: dolphin (Ubuntu)
Importance: Undecided
Status: New
** Tags: lockup performance ram thumbnailer
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dolphin thumbnailer takes too much ram
https://bugs.launchpad.net/bugs/521349
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